5.3 Pregnancy and childbirth

Chapter 5.3a The physiology of pregnancy and childbirth

Learning points

At the end of this chapter you will:

• understand the physiology of conception

• be able to recognise the stages of development of the embryo/fetus

• be able to describe the physiological changes of pregnancy

• be able to describe the changes that occur in normal labour

• be able to describe the physiological changes of the postnatal period (the puerperium).

Estimated time for chapter: 140 minutes.

Introduction

Section 5.2 was dedicated to the roles of the reproductive system of both the male and the female, including the production of gametes, and the provision of an environment in which these gametes can meet to produce a zygote. This chapter explores what happens following the time of conception, which is when the gametes meet, and follows the stages of development of the embryo and fetus, together with the physiological changes that occur in the mother at this time. The chapter concludes with a description of the physiology of childbirth and of the puerperium, which is the 6-week period that follows childbirth, during which time the mother’s body begins to return to its pre-pregnant state.

The formation of the embryo

Conception

‘Conception’ is the term used to describe the fusion of one of the millions of spermatozoa in the ejaculated sperm with the ovum, so forming a fertilised egg (zygote). In natural conception this fusion most commonly occurs in one of the fallopian tubes, within a few hours of ovulation. It is estimated that the ovum is viable for no more than 48 hours. This provides the spermatozoa with a relatively short window of opportunity to meet up with the ovum in any one menstrual cycle.

A spermatozoon reaches the fallopian tube from the vagina by means of the waving action of its flagellum (the tail-like process that projects from its cell membrane). The energy required for this feat of long-distance swimming is derived from nutrients contained in the seminal fluid (see Q5.3a-1).

The exact timing of the fertile period is unpredictable, as it depends on the timing of ovulation, which is variable even for women with regular menstrual cycles. It is recognised that women with regular cycles can ovulate earlier than day 7 and later than day 21 in a 28-day cycle. This, of course, has implications for the ‘natural family planning’ methods that can be used either to plan conception or to prevent pregnancy. This is why recognition of the changes in the consistency of cervical mucus is so important for the success of these methods.

Out of the millions of spermatozoa that are ejaculated, only a few hundred reach the fallopian tubes. When these spermatozoa reach the ovum, only one will be permitted to penetrate the cell membrane of the ovum. As soon as penetration has occurred, there is a change in the cell membrane that prevents the remaining spermatozoa from attaching (Figure 5.3a-I). The nuclei of the male and female gametes contain only 23 single chromosomes, rather than 23 pairs. After fusion of the ovum and sperm, their nuclei fuse to form 23 pairs of chromosomes, giving a combination of genes which is totally unique to that zygote. Within a few hours this new nucleus divides, and the zygote begins to form into the ball of cells known as the embryo.

Figure 5.3a-I • A recently fertilised ovum after a single division of the nucleus
• Spermatozoa that did not manage to penetrate the egg can be seen outside the cell membrane.

Development of the fetus to the time of delivery

From about 10 weeks of gestation the embryo is termed a ‘fetus’. The fetus has primitive limbs and facial features, and all the rudimentary organs in place. At this time the fetus is about 2.5 centimetres in length.

Nourishment of the fetus

The fetus obtains the nutrients it requires from the mother’s circulation. It is generally believed in conventional medicine that, except in cases of extreme starvation, the fetus can obtain all it needs from the mother’s bloodstream, and so will not necessarily suffer if the mother cannot have a good diet (e.g. in the case of morning sickness). Deficiency of folic acid in the maternal diet is the obvious exception to this. This is not the view held in Chinese medicine, in which the precise content of the diet of the pregnant woman is believed to have an important bearing on the health of the developing organs of the fetus.

However, the mother may suffer as her nutrients are being diverted to nourish the developing fetus and support the growth of the placenta. Deficiencies of iron and calcium are well recognised to affect women in pregnancy. These can than lead to anaemia and weak teeth. It is very likely that many more vitamin and mineral deficiencies can occur, which may partly explain the specific food cravings that many women experience during pregnancy. Although some of the foods craved may be bizarre in nature, the most common cravings are for fruit juice and dairy products, indicating a need to replace vitamins such as vitamin C and minerals such as calcium.

The main source of energy for the fetus is glucose. Glucose is also used to make the fats required by the fetus. Excessive glucose, a problem which occurs in maternal diabetes, will stimulate growth and cause excessive fat formation, and so can lead to an overlarge baby. Maternal amino acids are used to make the proteins required to build the structure of the tissues of the fetus. The wastes that the fetus produces are removed by the placenta into the maternal blood.

The fetal circulation

The circulation of the fetus has some important differences to that of a newborn baby. The blood enters the fetus through the umbilical cord, and first passes through the liver. It then is pumped through the heart, and thence to the rest of the body, before being redirected out through the umbilical cord. One major difference in this circulatory pattern is that relatively little blood is passed through the lungs, which in the fetus are filled with fluid, and are not a source of oxygen. To enable this circulation pattern to occur, the fetal heart retains a hole in its central wall, which permits the exchange of blood between the right and the left sides of the heart.

At birth, the lungs are expanded suddenly with the baby’s first cry. This expansion diverts a lot of blood into the vessels of the lungs for the first time. This has the remarkable effect of altering the pressure of blood within the rest of the fetal circulation so that the ‘hole’ in the heart is closed by means of a flap of tissue, and the blood flow in the umbilicus diminishes markedly. Within a matter of seconds the whole pattern of blood flow in the fetus is transformed. Within a few minutes the pulsation of blood in the umbilical cord stops, and the cord can be tied off. What used to be the life source for the fetus now becomes a redundant stump, commonly known as the ‘tummy button’.

The fetal digestive system

The gastrointestinal tract is relatively quiet in the fetus. As the fetus matures, it swallows amniotic fluid, which is then absorbed through the intestines and then excreted back into amniotic fluid cavity by the kidneys. By the end of pregnancy the intestines of the fetus contain a black sticky form of faeces called meconium. This is composed largely of epithelial cells that have been shed from the growing intestinal lining.

The fetal lungs

The fluid in the developing fetal lungs is in direct communication with the amniotic fluid through the mouth and nose. A circulation of this fluid is maintained by the breathing movements that occur with increasing regularity in the developing fetus. As the fetus reaches full maturity, the lungs secrete an oily substance, called ‘surfactant’, into the alveoli. After birth, surfactant enables the newly expanded air spaces to remain in their patent state. In premature babies, insufficient surfactant can result in a tendency for the alveoli to collapse. Deficiency of surfactant is one of the causes of the severe respiratory problems that can affect premature babies.

The fetal immune system

The immune system of the fetus begins to develop by week 20 of pregnancy. After this time the fetus is able to produce its own antibodies. Nevertheless, this response is not fully mature until some weeks after birth. The fetus gains extra protection from infection in the womb by maternal antibodies, which are able to cross the placenta. These antibodies have a life of a few weeks, and so continue to protect the newborn for a couple of months or so after the birth.

The progression of all the changes that occur in the fetus during its development are summarised in Table 5.3a-I (see Q5.3a-3).

Table 5.3a-I The stages in the development of the fetus

Age of gestation	Length of fetus	Stage of development of fetus
14 weeks	6 cm	All organs present in rudimentary form Limbs, muscles and bones all formed, baby has free movement. Sex organs developed Heartbeat strong and fast
15–22 weeks	16 cm	Hair, eyebrows, fingernails and fingerprint all formed; eyelids remain closed Baby’s movement can be felt by mother
23–30 weeks	24 cm	Movement is vigorous, baby can respond to touch and sound Baby can swallow, may get hiccups Urine is formed by the kidneys Eyelids open from time to time At 28 weeks the baby has a good chance of survival if born prematurely
31–40 weeks		Fat is laid down beneath the skin of the baby, making it plump and less wrinkly At 34 weeks most babies find a head-down position, and movements become more restricted due to lack of space

The physiological changes of pregnancy

The hormones of pregnancy

The developing embryo secretes the hormone HCG into the endometrium very soon after implantation. This means that at about day 21 after the last menstrual cycle the ovaries receive a signal that implantation has occurred. HCG stimulates the corpus luteum to continue to produce oestrogen and progesterone. Without this stimulus, the corpus luteum would degenerate rapidly, and the resulting drop in oestrogen and progesterone would lead to menstruation within a few days.

HCG is produced in large amounts during the first third (trimester) of the pregnancy. It is this hormone that can be detected from a sample of the mother’s urine and is used as the means of testing for pregnancy. A simple HCG test, which can be bought in the UK at a chemist, can indicate pregnancy even earlier than week 6 of gestation (2 weeks after the ‘missed period’).

Oestrogen is secreted in increasing amounts throughout pregnancy. This initially is produced by the corpus luteum, but is later produced by the placenta. Oestrogen brings about the increased fleshiness that is characteristic of pregnancy. The cervix becomes swollen and soft, and the breasts and nipples enlarge. Oestrogen also stimulates the increased vaginal discharge that is a normal feature of pregnancy. It also promotes an increased blood supply to all tissues. The amount of blood pumped through the heart increases, and the blood vessels dilate. In healthy pregnancies this results in a drop in the blood pressure. The healthy ‘glow’ commonly seen in middle to late pregnancy is a result of the effect of oestrogen on the blood supply to the skin.

Like oestrogen, progesterone is also produced initially by the corpus luteum, and then by the placenta. One important action of progesterone is to cause muscle and ligamentous relaxation. This effect is very marked on the muscular wall of the uterus, but excessive relaxation of the smooth muscle of the oesophageal sphincter, the bowel and the ureters may also occur. This effect of progesterone can result in some of the most common minor complications of pregnancy, including heartburn, constipation and tendency to urinary infections. Relaxation of the ligaments of the pelvis and lower back is important to allow for the passage of the baby during labour. However, this can lead to some of the painful musculoskeletal conditions of pregnancy, such as low backache, sacroiliac strain and pain in the symphysis pubis. Progesterone also tends to increase the body temperature. The placidity of pregnancy is attributed to a calming effect of progesterone on the brain.

Other hormones important in pregnancy include prolactin from the pituitary gland, adrenal corticosteroids and thyroid hormones. Prolactin stimulates the development of the milk-producing glands within the breast in the last 10 weeks of pregnancy. The adrenal corticosteroids are important to help the body deal with the demands of pregnancy, but in excess may lead to weight gain, high blood sugar and high blood pressure. The thyroid hormones play a role in the regulation of increased growth. Under the influence of oestrogen, the thyroid gland may enlarge to twice its normal size. Occasionally, if this enlargement is excessive, a goitre may develop.

The first symptoms of pregnancy

The first symptoms of pregnancy may be felt as early as the first 2 weeks after conception. Some women are aware of a different feeling even before the first missed period, and some may experience nausea or breast tingling at this early stage. It is more usual that symptoms are experienced at around week 6 of gestation. The most common include breast tingling or tenderness, nausea, and sensitivity to certain smells or tastes. The missed period is not a universal experience. Some women may have a painless bleed at 4 weeks, and even at 8 weeks of gestation, despite having a healthy pregnancy. As well as being a potential source of great anxiety, this form of bleeding can very much confuse the dating of the pregnancy, as the estimate of the length of the gestation normally relies on the date of the last menstrual period.

The effects of the enlarging uterus

As the embryo develops into a rapidly growing fetus, the uterus and the placenta enlarge to accommodate the growth and increasing nutritional requirements. At about 12 weeks of gestation, the amniotic sac is 10 centimetres in diameter and the uterus can be felt just above the pubic bone. At 20 weeks of gestation, the top of the uterus is at the level of the umbilicus, and by 36 weeks the uterus has reached the level of the xiphisternum. Amazingly, the remaining abdominal contents continue to function relatively normally, despite their increasingly cramped conditions.

However, certain problems can arise from the compression of the abdominal organs. In particular, compression of the abdominal aorta can lead to discomfort and faintness when lying supine (on the back) in late pregnancy. Restriction of the free flow of blood in the deep pelvic veins can contribute to the development of varicose veins, haemorrhoids and ankle swelling. Heartburn can be very severe in late pregnancy, as the uterus presses on the stomach from below. Occasionally, nerve compression can cause areas of pain and tingling. The most common site for this problem is down the front of the thigh, a result of the compression of a nerve which runs down from the crease of the groin. Rapid growth of the uterus can also lead to stretch marks and itching of the skin of the abdomen. Both these problems are compounded by the excessive weight gain that can complicate some pregnancies.

Changes in the uterus, cervix and vagina

The uterine muscle fibres lengthen markedly during pregnancy, thus allowing for the elongation of the uterus. The natural tendency for these fibres to contract becomes more pronounced. Mild contractions of the uterus start to occur from very early in pregnancy. Some, but not all, women become aware of these contractions, known as ‘Braxton–Hicks contractions’ from about 20 weeks of pregnancy. The sensation is usually described as a painless tightening of the abdomen, which lasts for a few seconds. Some women do describe the sensation as painful, akin to period cramps, and for this reason, Braxton–Hicks contractions sometimes can be confused with the onset of labour. Braxton–Hicks contractions increase in frequency and intensity as the time for the onset of labour approaches.

During pregnancy, the cervix and vagina respond to the increased levels of oestrogen and progesterone. The cervix becomes softer in consistency, a change that can be detected by a skilled examiner at as early as 8 weeks of gestation. This change occurs in preparation for the dilatation that has to occur during the first stage of labour. The vaginal walls also change in consistency to allow for the expansion that will be necessary to allow the birth of the baby. In addition, an odourless vaginal discharge is produced. This normal feature of pregnancy can be distressing for those women who are unprepared for its occurrence.

Changes in the maternal circulation

As pregnancy progresses, the blood vessels of the mother dilate, and an increased volume of blood circulates through them. These changes are to accommodate the increased requirements of the blood vessels in the placenta. Although the actual number of red blood cells is increased in a pregnant woman, usually the concentration of haemoglobin within them is slightly less than in the non-pregnant state. This can mean that a blood test will indicate anaemia. If this finding is mild, it need not be treated. However, many women will be offered treatment with iron tablets if the anaemia is severe, or if symptoms such as tiredness or dizziness develop.

The heart works much harder in pregnancy, as it has to pump up to 50% more blood than usual. The pulse is recognised to become more full and rapid in pregnancy, and this is accompanied by feelings of warmth. The ‘slipperiness’ that is a characteristic of pregnancy to a Chinese medicine practitioner is probably equivalent to this conventionally recognised pulse change.

Many women become more aware of palpitations in pregnancy. Conventionally, this symptom is not usually considered to be serious.

Changes in the respiratory, urinary and digestive systems

After about week 30 of pregnancy, the downward movement of the diaphragm becomes more restricted, and this is compensated for by an increased expansion of the ribcage during breathing. Some women will easily become breathless on exertion as this change develops.

The kidneys are more active in pregnancy, as they have to deal with the extra waste products coming from the fetus. More urine is produced. The muscles of the urinary system become more relaxed under the influence of progesterone. As previously mentioned, this can lead to an increased tendency to bladder infections. The risk of these infections spreading to involve the kidneys (pyelonephritis) is also increased in pregnancy.

The most common changes to affect the digestive system are spongy gums, heartburn and constipation. All these changes are results of the effect of progesterone. There is also an increased tendency to gum disease (gingivitis). For this reason, women are encouraged to make at least one visit to the dentist during pregnancy.

Weight gain

By the end of pregnancy, the fetus and the placenta together should weigh just over 4 kilograms. It is also normal for the mother to put on some weight as uterine muscle and breast tissue develop, and also as fat stores are laid down around the abdomen, buttocks and thighs. These fat stores will be drawn on in the first few months after birth as the mother breastfeeds. Adding up these different elements, the ideal weight gain in pregnancy is estimated to be around 11 kilograms.

However, there can be enormous variations around this ideal. Sometimes this can be because the woman herself either loses or gains weight during the pregnancy. Less commonly, abnormal weight gain may be an indication of poor fetal or placental growth, or, conversely, excessive accumulation of amniotic fluid. The most common problem with weight gain in pregnancy is that too much fat is laid down. The current advice is that a pregnant woman should eat a normal nutritious diet, and should not ‘eat for two’.

Psychological changes in pregnancy

Ideally, the psychological changes of pregnancy are positive ones. Pregnant women often report feeling calm and happy in the later stages of pregnancy, an experience attributed to the effects of progesterone. However, 5–10% of women develop depression during their pregnancy. This depression seems to be more common in first pregnancies, and in women who have poor social support. Often in such cases, there may be deep unaddressed fears about the labour, giving birth to a malformed child, or coping with caring for a baby. Also, many women grieve for the loss of their figure and freedom. Women who suffer from depression in pregnancy are more likely to develop postnatal depression (see Q5.3a-4).

Information Box 5.3a-I Pregnancy: comments from a Chinese medicine perspective

According to Chinese medicine, after conception the Blood and Yin associated with menstruation accumulate in the Chong and Ren Channels to nourish the developing fetus. As a consequence, the mother becomes relatively Blood and Yin Deficient, and her Yang becomes relatively Hyperactive. This means that Heat can easily accumulate during pregnancy.

The Spleen and the Kidneys are particularly important in supporting the nourishment and growth of the fetus, and so there may be a tendency to Deficiency of Spleen and Stomach Qi, with Accumulation of Damp and also Deficiency of Kidney Qi. The Liver is responsible for the smooth flow of Qi. As pregnancy is a time of accumulation of the Vital Substances in the lower Jiao, Liver Qi can easily Stagnate.

All these syndromes are more likely in those women who have a pre-existing imbalance in one or more of these Organ functions. Most of the complications of pregnancy can be interpreted from a Chinese medicine perspective as consequences of these common underlying syndromes.

The physiology of childbirth

All the physiological changes of pregnancy so far described are gradual in development. In a healthy pregnancy, most women adjust well to these changes as they progress over the 40 weeks of gestation. The onset of labour is quite different. All of a sudden the woman’s body is thrown into a series of profound changes, which escalate rapidly and culminate in the birth of the baby and the placenta, usually within a timescale of 24 hours.

The initiation of labour

The precise trigger for the onset of labour is not clearly understood. It is known that the uterus becomes more sensitive to the pituitary hormone oxytocin during late pregnancy. It is likely that a surge in the release of oxytocin from the pituitary actually brings about the relentless wave of contractions that are characteristic of established labour. It may be that it is a hormonal factor released from the maturing fetus, such as an adrenal corticosteroid, that actually stimulates this surge. It is recognised that external factors, such as shock, injury and fever, can stimulate early labour, and anxiety and exhaustion can delay the progression of labour.

As the time for labour approaches, the Braxton–Hicks contractions of the uterus become more frequent. Usually, at about 2 weeks before the onset of labour, the head of the baby drops into the bowl of the pelvis. This descent, known as ‘engagement’, often brings about a feeling of more comfort in the diaphragmatic area, as more space is created. In some pregnancies, engagement does not occur until after the onset of labour. In a few of these, this may be because the baby is not in the correct head-down, posterior-facing position.

Established labour is characterised by the onset of regular painful contractions that cause the tiny canal of the cervix to start to widen (dilate). In many women this transition between Braxton–Hicks contractions and labour contractions is not clear-cut. In these women, there may be a period of a few days in which the contractions are mildly painful and regular from time to time. Vaginal examination during this time will show that the cervix has not yet started to dilate. As cervical dilatation begins, a plug of mucus is released, which appears as an odourless blood-stained discharge called a ‘show’.

Healthy established labour involves regular contractions, which gradually become more frequent and sustained. A typical pattern is that the contractions start to occur at intervals of over 15 minutes and last for only a few seconds. As the cervix gradually dilates, the interval between contractions shortens to less than 5 minutes, and the pain of the contraction lasts for 1–2 minutes. As this progression occurs, the contractions become more painful. Initially, the woman will be able to carry on usual activities between the contractions. The pain at this stage is often compared to that of period cramps. It is usually felt in the lower abdomen and low back.

In some women, the amniotic sac ruptures at this early stage, leading to a trickle or a gush of clear fluid. Occasionally, this rupture occurs before the onset of labour. This can then stimulate the onset of labour. If labour does not start within 24 hours of the ‘breaking of the waters’, there is a potential risk of infection, and so labour may have to be induced medically.

The first stage of labour

Labour is described in terms of three stages. The show and the onset of regular painful contractions herald the first stage of labour. This first stage is the part of labour in which the canal of the cervix dilates to a diameter of about 10 centimetres. In this stage there is only a small downward movement of the baby.

In first pregnancies, a normal first stage can last up to 36 hours, although less than 24 hours is more usual. For many women who have a prolonged first stage, for much of this period the initial dilatation of the cervix is slow and the contractions are bearable. Usually, it is only in the later part of the first stage that the contractions become very strong. In subsequent pregnancies the first stage lasts only a few hours, and the progression to very strong contractions is more rapid.

As the first stage of labour becomes established, the pain of the contractions increases markedly. As the cervix dilates to greater than 5 centimetres, the pain causes the woman to go inward, stop talking and lose eye contact with the birth attendants. The respite between the contractions shortens down to only a few seconds as the contractions last for longer and become more frequent. If this painful stage is prolonged, the woman can become exhausted. For this reason, it is now common practice to encourage the woman to continue to eat light starchy food in the early part of the first stage of labour. Glucose drinks are very often recommended by midwives in the later part of the first stage, to sustain the woman as she goes through this ‘marathon’.

The transition between the first and second stages of labour

The transition time is when the cervix reaches its maximal dilatation. It is at this time that contractions are at their most painful. Very often, the woman feels totally overwhelmed by what she is experiencing. Some women experience great fear or panic, believing that they are about to die. Other women become aggressive and abusive. Some may insist that they can no longer cope with the pain, and might demand medical pain relief. However, these behaviours are often signs that labour is progressing well. This transitional time usually lasts less than 30 minutes.

Occasionally, the woman has a desire to push during the transitional stage. If this occurs, she will be advised by the midwife to avoid pushing, until it is certain that the cervix is fully dilated. This is because a premature onset of pushing can cause the cervix to tear.

It is usually around the time of transition that the waters break if they have not done so already.

The second stage of labour

The second stage of labour is the stage in which contractions of the uterus are combined with the woman voluntarily pushing her abdominal muscles. This combined action forces the baby downwards through the pelvic canal. The second stage ends with the birth of the baby. It should last no more than 2 hours.

The second stage is characterised by the experience of the urge to push. Generally, the contractions are very frequent and strong, but may be more bearable than in the first stage. This means that if a woman can be supported through the transition without resort to medical pain relief, she may not need to request it for the second stage.

The forceful downward contractions encourage the head of the baby to descend down the pelvic canal, usually with the face directed backwards. The mother begins to feel an intense pressure as the head enters the vagina. Very commonly, women panic at this stage, fearing that they are going to open their bowels. This is because the feeling of fullness can also be sensed in the rectum. The downwards descent of the head can be seen by the birth attendant a few contractions before it is actually delivered.

Once the head has reached the perineum, the surrounding tissues become very tightly stretched. At this point the woman feels an excruciating ‘bursting’ sensation. It is at this stage that the tissues of the vaginal wall and perineum may tear. Ideally, tearing can be prevented by controlling the force of the contractions. To enable this, the midwife will usually advise the women when to push, and when to avoid pushing, by the use of breathing exercises. The midwife will also try to control the descent of the baby’s head with manual pressure. However, often, the instinctive urge to push is too great to be controlled, and tearing cannot be avoided. The practice of episiotomy, in which a cut is made in the perineum by the midwife, is now becoming outmoded. It is now recognised that most natural tears heal more efficiently than the surgical cut of the episiotomy.

Once the head has been delivered, the midwife checks that the umbilical cord is not tightly wrapped around the baby’s neck. If it is, the midwife will free the cord before the rest of the baby’s body is delivered. This is a common occurrence, which, if managed correctly, usually does not have serious consequences. Delivery of the rest of the baby’s body usually occurs within another one or two contractions. A healthy newborn baby will make a cry within a few seconds. If there are no complications, it is common practice to hand the baby to the mother straight away to allow it to suckle. Ideally, time should be given (2–3 minutes) to allow the pulsation of blood in the vessels of the umbilical cord to stop before the cord is clamped and cut.

Once the baby has been delivered, there is usually a dramatic cessation of pain and discomfort for the mother. She often experiences a surge of renewed energy as she first sees and holds her new baby.

The third stage of labour

The third stage of labour involves the delivery of the placenta and the amniotic membranes (afterbirth). By the time of the labour, the placenta is a grapefruit-sized mass of soft tissue, with the colour and consistency of fresh liver. After the umbilical vessels have stopped pulsating, the placental blood vessels contract, so allowing the placenta to come away from the wall of the uterus without there being excessive blood loss. After about 10–20 minutes, continued contractions of the uterus force the separated placenta, amniotic membranes and remaining umbilical cord out through the vagina. A smooth third stage is enabled by the midwife, who applies pressure to the uterus, and controlled traction to the cord as the placenta passes out of the uterus.

The uterus continues to contract after the expulsion of the placenta, so that its rich network of blood vessels is encouraged to shut down. These continued contractions are encouraged by the suckling of the baby, as this stimulates a natural release of oxytocin from the mother’s pituitary.

To facilitate this process, it is very common practice to administer an injection of an oxytocin-like drug called syntometrine to the mother. This ensures that the contraction of the uterus occurs rapidly so that blood loss is minimised. This injection is usually given into the mother’s thigh just after the delivery of the baby’s head. This treatment is known to reduce the incidence of severe blood loss by half. The main complication of syntometrine use is that the uterus may contract prematurely around the placenta, so preventing its removal. If this occurs, a minor operation is required so that the placenta can be removed manually.

The contractions of the third stage are much less painful than those of the first and second stages. Often the mother may be unaware that this stage has taken place, as she is so involved with holding and suckling her newborn baby.

After the delivery of the placenta, it is inspected by the midwife to check that it is intact, and to estimate the approximate blood loss. The amount of blood lost in an average labour is around 400 millilitres. An amount greater than 500 millilitres is considered excessive, and replacement therapy, either by means of iron or blood transfusion, may be considered necessary. If there has been a tear, this is then stitched, either by the midwife or the doctor in attendance.

The effect of labour on the fetus

During labour, the head of the human fetus experiences much greater pressure than occurs during the birth of other mammals. The soft, immature plates of bone that form the skull are often ‘moulded’ into an elongated shape during the passage of the head through the pelvic canal. A more normal shape is reassumed over the course of the few days after birth. Severe moulding can occur if the second stage is prolonged, or if assisted methods of delivery such as forceps have to be used.

The baby always suffers from a period of low oxygen supply during labour. This can affect the heart rate of the baby, which is monitored by the midwife. A prolonged period of abnormal fetal heart rate is taken seriously. If this occurs, it may lead to the use of medical interventions to speed up the labour, or the decision to proceed to a caesarean section.

Another response of ‘fetal distress’ is that the fetus opens its bowels during the course of labour. The appearance of black, sticky meconium in the leaking amniotic fluid is a warning sign of fetal distress in labour. If meconium has been released, not only does this indicate possible distress in the fetus, but there is also a risk of the meconium being inhaled by the fetus. Therefore, the release of meconium is another reason why medical intervention may have to take over the course of the labour, so that the baby is delivered as soon as possible.

There is no doubt that even uncomplicated labour is stressful for the fetus. The fetal adrenal glands are stimulated to produce excessive amounts of adrenaline and corticosteroids in response to this stress. It is believed that high levels of these hormones are important in promoting the dramatic changes that occur in the cardiovascular and respiratory systems of the baby just after birth.

Information Box 5.3a-II Labour: comments from a Chinese medicine perspective

In Chinese medicine, labour is believed to be a time when Yang expels Yin. After 40 weeks of relative Stagnation of Qi in the Lower Jiao, a powerful and smooth downward movement of Qi leads to the expulsion of the fetus. This has been described also in terms of ‘Qi moving Blood’. A healthy labour is dependent on healthy Blood and Qi. Healthy Spleen, Kidney and Liver Organs are particularly important in ensuring that a labour progresses smoothly through all three stages.

The physiology of the puerperium

The puerperium is defined as the 6-week period that follows childbirth. During this time, the uterus slowly returns to its normal size and shape. At the end of the puerperium, any trauma to the vagina and perineum should have healed completely. The puerperium is also the time when the foundations of the relationship between the mother and the baby are established.

In many cultures across the world, the time of the puerperium is a period when the woman is confined to bed-rest. This was also the practice in ancient China. This tradition allows the mother to divert all her attention into bonding with her child, to establish a pattern of breastfeeding, and to rebuild her own reserves of energy. However, in the developed world, this practice is not the norm. Many women now choose to be up and about on the day following labour, and, once at home, may resume normal activities such as shopping or housework straight away.

Immediately following a normal birth, the pelvic area of the mother is in a bruised and torn state. It is usual for there to be considerable discomfort in this area for the next few days, which can make sitting, walking and going to the toilet painful. Often it is difficult to pass urine for a few hours after labour because of pain and swelling in the region of the urethra. There is an increased risk of urinary infection at this time. Unless there has been a serious tear, these problems resolve rapidly.

For the first few weeks after birth, an odourless watery and blood-stained discharge, known as ‘lochia’, is usual. This discharge comes from the contracting uterus. It gradually diminishes with time, and should have stopped by the end of the puerperium.

Breastfeeding

Breastfeeding (lactation) is usually encouraged from the moment the baby is born. The suckling reflex does not have to be learned. As long as the baby is allowed to find the right position on the nipple, it will suckle efficiently. The correct positioning of the baby on the breast is absolutely essential if breastfeeding is to be problem free. Sore and cracked nipples are a very common initial experience in the first few days of feeding. This problem is worse if the positioning of the baby is not correct. This potentially preventable problem is the most common reason why many women give up breastfeeding after only a few days.

Normal milk is not produced until a few days after the birth. Until this time, a yellowish, antibody-rich fluid, called ‘colostrum’, is produced. This fluid is believed to be highly beneficial to the digestive and immune systems of the baby. Even if the mother has made a prior decision not to breastfeed, she may be encouraged to do so at least for the first few days, so that the baby can receive the colostrum. When the normal milk ‘comes in’, the breasts become engorged and uncomfortable. This discomfort is relieved over the next few days as the baby continues to suckle, when a balance is achieved between milk production and feeding.

The suckling is a stimulus for the release of two pituitary hormones. Prolactin stimulates the production of the milk from the lobules of the breast, and oxytocin stimulates the ‘let down’ of this milk into the lactiferous ducts, which open out into the nipple. Oxytocin also has a beneficial effect on maintaining the contraction of the uterus, which continues over the ensuing few weeks. For this reason, some women will experience mild period-like cramps in the early days of breastfeeding.

If the mother chooses not to breastfeed, it is normal for there to be period of 1–2 weeks of uncomfortable engorgement. The drug bromocriptine, which inhibits the production of prolactin from the pituitary, may be prescribed to alleviate this discomfort. Because of potentially severe side-effects of this drug, it is usually given only in situations when it is considered very important to suppress lactation, such as following the death of a baby.

Milk is usually produced according to the demand of the baby. The more the baby feeds, the more milk is produced. However, some women manage to produce much more milk than others, and can experience problems from overflow of milk at inappropriate times. It is unusual for the baby to fail to thrive because of insufficient milk production. However, illness, stress and anaemia can all contribute to poor milk supply.

Breast milk is rich in fat and sugars. It also contains all the vitamins and minerals the baby requires for at least the first 6 months. It may also contain traces of drugs and toxins that have entered the circulation of the mother. Some drugs enter breast milk more easily than others.

The breastfeeding mother requires more nutrients than a mother who chooses not to breastfeed. She will draw on her reserves of body fat, and will also require a diet rich is vitamins and minerals. It is particularly important that calcium and iron are available from the diet. If these are deficient, the mother will draw on her own reserves of these minerals. For this reason, weak teeth, thinned bones and anaemia can develop during the weeks to months of breastfeeding. It is not uncommon for the skin to dry and the hair to become lustreless and thin in this time, a result of the cumulative depleting effect of pregnancy and lactation.

Psychological changes in the puerperium

For the mother, the time following the birth is characterised by a roller coaster of emotions. There are a number of understandable reasons why these emotional changes might occur. First, a profound emotional adjustment is necessary to the arrival of the baby and the prospect of ‘life never being the same again’. Second, in the first few days after childbirth, the body has to recover from an exhausting physical upheaval, and then may be expected to give more of its nutritional reserves in breastfeeding. In addition to this, there are dramatic changes in the hormone balance of the body, as the high levels of oestrogen and progesterone suddenly drop with the delivery of the placenta. The effect of these natural changes may be compounded by additional factors such as the shock of suffering a traumatic delivery, recovering from a caesarean section, or the finding of congenital defects in the baby.

However, some women are elated after the birth, and this feeling may be sustained for days to weeks. Many experience a brief period of volatile emotions, often called the ‘baby blues’. This period occurs at around the third day after the birth. The mother may feel down, weepy or irritable. Normally this period of low mood should last for no more than a few days. If this state is prolonged it may be a warning sign of the more severe condition of postnatal depression.

The first 6 weeks after childbirth are characterised for most parents by periods in which the baby cries inconsolably, very disturbed nights, and anxiety for the baby’s health. All these are bound to be draining, but by the end of a healthy puerperium, the mother should still feel hopeful and that she is coping.

Lack of sexual interest is normal in the first few weeks after childbirth. This may be prolonged in the breastfeeding mother. This again is normal, and is thought to be a consequence of the hormones that maintain the state of lactation. The midwife or doctor may advise the mother to refrain from sexual intercourse for the first 6 weeks after childbirth in order to give the perineal tissues a chance to heal.

In women who are not breastfeeding, fertility may return very quickly, and so contraceptive measures are advised to be used from 3 weeks after the birth. Although breastfeeding is believed to inhibit ovulation, pregnancy has been known to occur in breastfeeding mothers. Therefore, contraceptive advice is given to all women at the end of the puerperium, irrespective of their choice of feeding method.

Information Box 5.3a-III The puerperium: comments from a Chinese medicine perspective

In Chinese medicine, it is expected that following childbirth the mother will be relatively depleted in Blood and Kidney Qi. Nevertheless, an uncomplicated labour can have very beneficial consequences, because it encourages a profound movement of Qi and so can clear Stagnation on many levels. If a woman can be supported through the puerperium so that her reserves of Blood and Qi are built up, she may actually experience an improvement in health and well-being through conceiving and giving birth to a child.

The mother’s Blood and the Kidneys should be supported during the puerperium by good nutrition and rest. Any stressful factors in this time will adversely affect both the Blood and the Kidneys, and ideally should be avoided.

In Chinese medicine, breast milk is believed to be drawn from the mother’s Blood and Essence (Jing). The possible negative effects of breastfeeding on the energy levels and calcium reserves of the mother accord with this interpretation. In light of this, it is understandable why certain cultures consider the 6-week confinement to be so important in protecting the mother’s reserves of energy. The positive energetic effects of breastfeeding are that it enables a smooth movement of Liver Qi. In keeping with this interpretation, many women describe how breastfeeding has a calming effect. Breastfeeding can improve appetite, and yet promote the loss of the fat that was laid down in pregnancy. This suggests that breastfeeding also has a beneficial effect on Spleen Qi, and stimulates the Clearance of Damp.

After the puerperium

The puerperium is considered to be the time required for the body to return to its pre-pregnant state. Of course this is not the case for those women who continue to breastfeed. Even for those who do not breastfeed, the weeks to months following the puerperium are a time of continuing adjustment to the arrival of the baby. Most women do not feel back to their ‘normal’ state for up to 1 year after the puerperium.

Chapter 5.3b Routine care and investigation in pregnancy and childbirth

Learning points

At the end of this chapter you will:

• be able to describe the structure of antenatal care as offered in the UK

• be able to describe the investigations that are performed in antenatal care

• be able to recognise the common medical interventions that may be offered during a normal labour

• be able to describe the structure of postnatal care as offered in the UK

• understand the experience of the woman receiving this care during pregnancy, labour and the postnatal period.

Estimated time for chapter: 90 minutes.

Self-test 5.3a The physiology of pregnancy and childbirth

1. In light of your understanding about the conventional medicine understanding of the requirements for a healthy conception, what sort of advice would you give to a couple who are planning to start trying for a baby?

2. What are the broad effects in pregnancy of:

(i) human chorionic gonadotrophin (HCG)

(ii) oestrogen

(iii) progesterone

(iv) prolactin?

3. From a conventional medicine perspective, what are the main health issues that predominate in the puerperium?

Answers

1. Your advice might cover the following topics:

• Timing: even with a regular menstrual cycle, the timing of ovulation may be erratic. Therefore regularly spaced intercourse may be more likely to result in conception than concentrating around the time of the middle of the cycle.

• Diet: a healthy balanced diet is important for both partners, as this is known to improve the health of the sperm and may increase the likelihood of implantation. A good supply of nutrients is essential for the developing embryo. Women are advised to begin folic acid supplementation before the time of trying to conceive.

• Drugs and toxins: some medical drugs (including the contraceptive pill), smoking and alcohol are all recognised to impair the health of the gametes, reduce the chances of conception and adversely affect the developing embryo. Ideally, these should all be stopped in the weeks leading up to the time of trying to conceive.

• Stress: stress is recognised to impair the sperm count, inhibit ovulation and impair implantation. Any lifestyle changes that might reduce sources of stress should be advised.

Additional advice from the Chinese medicine perspective might focus on the adverse effect of a range of internal, external and miscellaneous causes of disease. Topics such as the specific content of a nourishing diet, moderate exercise, avoidance of climatic extremes and calm emotions might be discussed.