The time when a woman carries a developing baby in her UTERUS. For the first 12 weeks (the first trimester) the baby is known as an EMBRYO, after which it is referred to as the FETUS.
Pregnancy lasts about 280 days and is calculated from the first day of the last menstrual period – see MENSTRUATION. Pregnancy-testing kits rely on the presence of the hormone beta HUMAN CHORIONIC GONADOTROPHIN (b HCG) which is excreted in the woman's urine as early as 30 days from the last menstrual period. The estimated date of delivery can be accurately estimated from the size of the developing fetus measured by ULTRASOUND (see also below) between seven and 24 weeks. ‘Term’ refers to the time that the baby is due; this can range from 38 weeks to 41 completed weeks.
Physical changes occur in early pregnancy – periods stop and the abdomen enlarges. The breasts swell, with the veins becoming prominent and the nipples darkening. About two in three women will have nausea with a few experiencing such severe vomiting as to require hospital admission for rehydration.
The aim of antenatal care is to ensure a safe outcome for both mother and child; it is provided by midwives (see MIDWIFE) and doctors. Cooperation between general practitioners, midwives and obstetricians means that pregnancies that are likely to progress normally are cared for in the community and only those needing special intervention are cared for at a hospital.
The initial visit (or booking) in the first half of pregnancy will record the history of past events and the results of tests, with the aim of categorising the pregnancy as to whether or not it is likely to be normal. Screening tests, including blood checks and ultrasound scans, are a routine part of antenatal care. The first ultrasound scan is done at about 11 weeks to date the pregnancy, with a further one done at 20 weeks – the anomaly scan – to assess the baby's structure. Some obstetric units will check the growth of the baby with one further scan later in the pregnancy or, in the case of twin pregnancies (see below), many scans throughout. Blood tests include checks for ANAEMIA, DIABETES MELLITUS, sickle-cell disease and THALASSAEMIA, as well as for the blood group. Evidence of past infections is also looked for; tests for RUBELLA (German measles) and SYPHILIS are routine, whereas tests for human immunodeficiency virus (see AIDS/HIV below) and HEPATITIS are being offered as there is compelling evidence that knowledge of the mother's infection status is beneficial to the baby.
Traditional antenatal care consists of regular appointments, initially every four weeks until 34 weeks, then fortnightly or weekly. At each visit the mother's weight, urine and blood pressure are checked, and assessment of fetal growth and position is done by palpating the uterus. Around two-thirds of pregnancies and labours are normal: in the remainder, doctors and midwives need to increase the frequency of surveillance so as to prevent or deal with maternal and fetal problems.
Women requiring more intensive surveillance have their management targeted to the specific problems encountered. Cardiologists will see mothers-to-be with heart conditions, and those at risk of diabetes should be cared for in designated clinics with specialist staff. Those women needing more frequent surveillance than standard antenatal care can be looked after in maternity day centres. These typically include women with mildly raised blood pressure or those with small babies. Fetal medicine units have specialists who are highly skilled in ultrasound scanning and specialise in the diagnosis and management of abnormal babies still in the uterus.
Chronic abdominal discomfort early in pregnancy may be caused by unruptured ectopic pregnancy, when, rarely, the fertilised OVUM starts developing in one of the FALLOPIAN TUBES instead of the uterus. The patient needs hospital treatment and LAPAROSCOPY. A ruptured ectopic pregnancy causes acute abdominal symptoms and collapse, and the woman will require urgent abdominal surgery.
These affect around 2 per cent of pregnant women and are detected by a laboratory test of a mid-stream specimen of urine; this is taken by asking the woman to discard the first part of the urinary stream and then to collect the next sample in a sterile container (the initial specimen is likely to be contaminated by bacteria living on the skin, so may be uninterpretable). The symptoms do not necessarily resemble those experienced by non-pregnant women. As they can cause uterine irritability and possible premature labour (see below), it is important to find and treat them appropriately.
is more prevalent in patients who are vegetarian or on a poor diet. Iron supplements are usually given to women who have low concentrations of HAEMOGLOBIN in their blood (less than 10.5 g/dl) or who are at risk of becoming low in iron, from bleeding, twin pregnancies and those with placenta previa (see below).
Early in pregnancy, vaginal bleedings may be due to a spontaneous (see below) or an incomplete therapeutic ABORTION. Bleeding from the genital tract between 24 completed weeks of pregnancy and the start of labour is called antepartum haemorrhage. The most common site is where the PLACENTA is attached to the wall of the uterus. If the placenta separates before delivery, bleeding occurs in the exposed ‘bed’. When the placenta is positioned in the upper part of the uterus it is called an abruption.
is sited in the lower part and blocks or partly blocks the cervix (neck of the womb); it can be identified at about the 34th week. Ten per cent of episodes of antepartum bleeding (see above) are caused by placenta praevia, and it may be associated with bleeding at delivery. This potentially serious complication is diagnosed by ultrasound scanning and may require a CAESAREAN SECTION (see below) at delivery.
with protein in the urine and swelling of the limbs is part of a condition known as PRE-ECLAMPSIA. This occurs in the second half of pregnancy in about 1 in 10 women expecting their first baby, and is mostly of no consequence to the pregnancy. However, some women can develop extremely high blood pressures which can adversely affect the fetus and cause epileptic-type seizures and bleeding disorders in the mother. This serious condition is called ECLAMPSIA. For this reason a pregnant woman with raised blood pressure or PROTEIN in her urine is carefully evaluated with blood tests, often in the maternity day assessment unit. The condition can be stopped by delivery of the baby, and this will be done if the mother's or the fetus’ life is in danger. If the condition is milder, and the baby not mature enough for a safe delivery, then drugs can be used to control the blood pressure.
Also called spontaneous abortion, miscarriage is the loss of the fetus. There are several types:
threatened miscarriage is one in which some vaginal bleeding occurs, the uterus is enlarged, but the cervix remains closed and pregnancy usually proceeds.
inevitable miscarriage usually occurs before the 16th week and is typified by extensive blood loss through an opened cervix and cramp-like abdominal pain; some products of conception are lost but the developing placental area (decidua) is retained and an operation may be necessary to clear the womb.
missed miscarriages, in which the embryo dies and is absorbed, but the decidua (placental area of uterine wall) remains and may cause abdominal discomfort and discharge of old blood.
is performed on nearly 200,000 occasions annually in England & Wales. Sometimes the woman may not have arranged the procedure through the usual health-care channels, so that a doctor may see a patient with vaginal bleeding, abdominal discomfort or pain, and open cervix – symptoms which suggest that the decidua and a blood clot have been retained; these retained products will need to be removed by curettage.
describes a slowing of the baby's growth. This can be diagnosed by ultrasound scanning, although there is a considerable margin of error in estimates of fetal weight. Trends in growth are favoured over one-off scan results alone.
is a condition that is more common in women who are overweight or have a family member with diabetes. If high concentrations of blood sugar are found, efforts are made to correct it as the babies can become very fat (macrosomia), making delivery more difficult. A low-sugar diet is usually enough to control the blood concentration of sugars; however some women need small doses of INSULIN to achieve control.
these can sometimes be detected before birth using ultrasound. Some of these defects are obvious, such as the absence of kidneys, a condition incompatible with life outside the womb. These women can be offered a termination of their pregnancy. However, more commonly, the pattern of problems can only hint at an abnormality and closer examination is needed, particularly in the diagnosis of chromosomal deformities such as DOWN'S SYNDROME (trisomy 21 or presence of three 21 chromosomes instead of two).
Chromosomal abnormalities can be definitively diagnosed only by cell sampling such as amniocentesis (obtaining amniotic fluid – see AMNION – from around the baby) done at 15 weeks onwards, and chorionic villus sampling (sampling a small part of the placenta) – another technique which can be done from 12 weeks onwards. Both have a small risk of miscarriage associated with them; consequently, they are confined to women at higher risk of having an abnormal fetus.
Biochemical tests on the pregnant woman's blood at different stages of pregnancy may be abnormal in some women carrying an abnormal fetus, for example, a high concentration of alpha-fetoprotein in babies with SPINA BIFIDA (defects in the covering of the spinal cord). There are several such useful tests which, in conjunction with other factors such as age, ethnic group and ultrasound findings, can provide a predictive guide to the obstetrician – in consultation with the woman – as to whether or not to proceed to an invasive test. These tests include pregnancy-associated plasma protein assessed from a blood sample taken at 12 weeks and four blood tests at 15–22 weeks – alpha-fetoprotein, beta human chorionic gonadotrophin, unconjugated oestriol and inhibin A. Ultrasound itself can reveal physical findings in the fetus, which can be more common in certain abnormalities. Swelling in the neck region of an embryo in early pregnancy (increased nuchal thickness) has good predictive value on its own, although its accuracy is improved in combination with the biochemical markers. The effectiveness of prenatal diagnosis is rapidly evolving, the aim being to make the diagnosis as early in the pregnancy as possible to help the parents make more informed choices.
In the UK, one in 34 babies is born a twin or triplet. In 1980, the rate was 1 in 52. This means that every year in the UK, about 12,000 sets of twins, 150 triplets and a handful of quads are born. Multiple pregnancies occur more often in older women and after certain fertility treatments (many of these being in older women) which has raised the incidence in recent years (see ASSISTED CONCEPTION).
Multiple pregnancies are now usually diagnosed as a result of routine ultrasound scans between 16 and 20 weeks of pregnancy. The increased size of the uterus results in the mother having more or worse pregnancy-related conditions such as nausea, abdominal discomfort, backache and varicose veins. Some congenital abnormalities in the fetus occur more frequently in twins: NEURAL TUBE defects, abnormalities of the heart and the incidence of TURNER'S SYNDROME and KLINEFELTER'S SYNDROME are examples. Such abnormalities may be detected by ultrasound scans or amniocentesis. High maternal blood pressure and anaemia are commoner in women with multiple pregnancies (see above).
The growth rates of multiple fetuses vary, but the difference between them and single fetuses are not that great until the later stages of pregnancy. Preterm labour is commoner in multiple pregnancies: the median length of pregnancy is 40 weeks for singletons, 37 for twins and 33 for triplets. Low birth-weights are usually the result of early delivery rather than abnormalities in growth rates. Women with multiple pregnancies require more frequent and vigilant antenatal assessments, with their carers being alert to the signs of preterm labour occurring.
Disparity between the size of the fetus and the mother's pelvis is not common in the UK but is a significant problem in the developing world. Disparity is classified as absolute, when there is no possibility of delivery, and relative, when the baby is large but delivery (usually after a difficult labour) is possible. Causes of absolute disparity include: a large baby – heavier than 5 kg at birth; fetal HYDROCEPHALUS; and an abnormal maternal pelvis. The latter may be congenital, the result of trauma or a contraction in pelvic size because of OSTEOMALACIA early in life. Disproportion should be suspected if in late pregnancy the fetal head has not ‘engaged’ in the pelvis. Sometimes a closely supervised ‘trial of labour’ may result in a successful, if prolonged, delivery. Otherwise a CAESAREAN SECTION is necessary.
In most pregnant women the baby fits into the maternal pelvis head-first in what is called the occipito-anterior position, with the baby's face pointing towards the back of the pelvis. Sometimes, however, the head may face the other way, or enter the pelvis transversely – or, rarely, the baby's neck is flexed backwards with the brow or face presenting to the neck of the womb. Some malpositions will correct naturally; others can be manipulated abdominally during pregnancy to a better position. If, however, the mother starts labour with the baby's head badly positioned or with the buttocks instead of the head presenting (breech position), the labour will usually be longer and more difficult and may require intervention using special obstetric forceps to assist in extracting the baby. If progress is poor and the fetus distressed, CAESAREAN SECTION may be necessary. Some obstetricians consider that the breech position poses enough of a threat to a baby that Caeserean Section should be the rule, especially for women who have not previously experienced labour.
Pregnant women who are HIV positive (see HIV; AIDS/HIV) should take antiviral drugs in the final four to five months of pregnancy. This reduces the risk of infecting the baby before or during birth by around 50 per cent. Additional antiviral treatment is given before delivery; the infection risk to the baby can be further reduced – by about 40 per cent – if delivery is by CAESAREAN SECTION. The mother may prefer to have the baby normally, in which case great care should be taken not to damage the baby's skin during delivery. The infection risk to the baby is even further reduced if he or she is not breast fed. If all preventive precautions are taken, the overall risk of the infant becoming infected is cut to under 5 per cent.
is now much less common in Britain than before the Abortion Act (1967) permitted abortion in specified circumstances. The cause is the passage of infective organisms from the vagina into the uterus, with Escherichia coli and Streptococcus faecalis the most common pathogenic agents. The woman has abdominal pain, heavy bleeding, usually fever and sometimes she is in shock. The cause is usually an incomplete abortion or one induced in unsterile circumstances. Antibiotics and curettage are the treatment.
The traditional definition is a birth that takes place when the baby weighs less than 2.5 kilograms (5½ pounds). However, in practice it refers to any birth that takes place before 37 weeks gestation. Between 5 and 10 per cent of babies are born prematurely, and in around 40 per cent of those the cause is unknown. PRE-ECLAMPSIA is the most common known cause; others include HYPERTENSION, chronic kidney disease, heart disease and DIABETES MELLITUS. Multiple pregnancy is another cause. In the vast majority of cases the aim of management is to prolong the pregnancy and so improve the outlook for the unborn child. This consists essentially of rest in bed and sedation, but there are now several drugs, such as RITODRINE, that may be used to suppress the activity of the uterus and so help to delay premature labour. Prematurity was once a prime cause of infant mortality but modern medical care has greatly improved survival rates in developing countries. The outlook for premature babies depends largely on their gestation – how long they have been in the uterus. Thus, a baby born at 22–23 weeks (17–18 weeks early) has less than a 1 in one hundred chance of surviving. UK recommendations are that such babies are not given intensive care unless parents request it after full discussion of the risks and the distress it might cause the baby and with the neonatologist's agreement. Once 24 weeks is reached, when most babies will weigh about 450–650 g (1–1½ lbs) about 28 per cent are likely to survive; for the survivors there is a risk of having moderate to severe disabilities and it is very difficult to predict early on which babies will do well. In this situation, parents are entitled to have the final say about whether to provide intensive care. By 26 weeks, the survival rate is 75% and intensive care is automatic unless complications have meant the baby has no hope of survival or its suffering outweighs its interests in continuing to live. (See NEONATAL INTENSIVE CARE.)
Also known by the traditional terms parturition, childbirth or delivery, this is the process by which the baby and subsequently the placenta are expelled from the mother's body. The onset of labour is often preceded by a ‘show’ – the loss of the mucus and blood plug from the cervix, or neck of the womb; this passes down the vagina to the exterior. The time before the beginning of labour is called the ‘latent phase’ and characteristically lasts 24 hours or more in a first pregnancy. Labour itself is defined by regular, painful contractions which cause dilation of the neck of the womb and descent of the fetal head. ‘Breaking of the waters’ is the loss of amniotic fluid vaginally and can occur any time in the delivery process.
The second stage of labour is from full cervical dilation to the delivery of the baby. At this stage the mother often experiences an irresistible urge to push the baby out, and a combination of strong coordinated uterine contractions and maternal effort gradually moves the baby down the birth canal. This stage usually lasts under an hour but can take longer. Delay, exhaustion of the mother or distress of the fetus may necessitate intervention by the midwife or doctor. This may mean enlarging the vaginal opening with an EPISIOTOMY (cutting of the perineal outlet – see below) or assisting the delivery with specially designed obstetric forceps or a VACUUM EXTRACTOR (ventouse – see below). If the cervix is not completely dilated or open and the head not descended, then an emergency Caesarean section may need to be performed to deliver the baby. This procedure involves delivering the baby and placenta through an incision in the mother's abdomen. It is sometimes necessary to deliver by planned or elective Caesarean section: for example, if the placenta is low in the uterus – called placenta praevia – making a vaginal delivery dangerous (see below).
The third stage occurs when the placenta (or afterbirth) is delivered, which is usually about 10–20 minutes after the baby. An injection of ergometrine and oxytocin is often given to women to prevent bleeding.
Pain relief in labour varies according to the mother's needs. For uncomplicated labours, massage, reassurance by a birth attendant, and a warm bath and mobilisation may be enough for some women. However, some labours are painful, particularly if the woman is tired or anxious or is having her first baby. In these cases other forms of analgesia are available, ranging from inhalation of NITROUS OXIDE GAS, injection of PETHIDINE HYDROCHLORIDE or similar narcotic, and regional local anaesthetic, such as an epidural (see ANAESTHESIA).
Once a woman has delivered, care continues to ensure her and the baby's safety. The midwives are involved in checking that the uterus returns to its normal size and that there is no infection or heavy bleeding, as well as caring for stitches if needed. The normal blood loss after birth is called lochia and generally is light, lasting up to six weeks. Midwives offer support with breast feeding and care of the infant and will visit the parents at home routinely for up to ten days.
All operative deliveries in the UK are now done in hospitals, and are performed if a spontaneous birth is expected to pose a bigger risk to the mother or her child than a specialist-assisted one. Operative deliveries include CAESAREAN SECTION, forceps-assisted deliveries and those in which vacuum extraction (ventouse) is used.
Absolute indications for this procedure, which is used to deliver nearly 20 per cent of babies in Britain, are cephalopelvic disproportion and extensive placenta praevia (for both, see above). Otherwise the decision depends on the clinical judgement of the specialist and the views of the mother. The rise in the proportion of this type of intervention has been put down to defensive medicine – namely, the doctor's fear of litigation (initiated often because the parents believe that the baby's health has suffered because the mother had an avoidably difficult ‘natural’ labour). In Britain, over 60 per cent of women who have had a Caesarean section try a vaginal delivery in a succeeding pregnancy, with about two-thirds of these being successful. Indications for the operation include:
absolute and relative cephalopelvic disproportion.
placenta previa.
fetal distress.
prolapsed umbilical cord – this endangers the viability of the fetus because the vital supply of oxygen and nutrients is interrupted.
malpresentation of the fetus such as breech or transverse lie in the womb.
unsatisfactory previous pregnancies or deliveries.
a request by the mother.
Caesarean sections are usually performed using regional block anaesthesia induced by a spinal or epidural injection. This results in loss of feeling in the lower part of the body; the mother is conscious and the baby not exposed to potential risks from volatile anaesthetic gases inhaled by the mother during general anaesthesia. Post-operative complications are higher with general anaesthesia, but maternal anxiety and the likelihood that the operation might be complicated and difficult are indications for using it. A general anaesthetic may also be required for an acute obstetric emergency. At operation the mother's lower abdomen is opened and then her uterus opened slowly with a transverse incision and the baby carefully extracted. A transverse incision is used in preference to the traditional vertical one as it enables the woman to have a vaginal delivery in any future pregnancy with a much smaller risk of uterine rupture. Women are usually allowed to get up within 24 hours and are discharged after four or five days.
Obstetric forceps are made in several forms, but all are basically a pair of curved blades shaped so that they can obtain a purchase on the baby's head, thus enabling the operator to apply traction and (usually) speed up delivery. (Sometimes they are used to slow down progress of the head, particularly in very premature babies where too rapid a delivery may be dangerous.) A ventouse or VACUUM EXTRACTOR comprises an egg-cup-shaped metal or plastic head, ranging from 40 to 60 mm in diameter with a hollow tube attached through which air is extracted by a foot-operated vacuum pump. The instrument is placed on the descending head, creating a negative pressure on the skin of the scalp and enabling the operator to pull the head down. Forceps have a greater risk of causing damage to the baby's scalp and brain than vacuum extraction, although properly used, neither type should cause damage to the baby.
Normal and assisted deliveries put the tissues of the genital tract under strain. The PERINEUM is less elastic than the vagina and, if it seems to be splitting as the baby's head moves down the birth canal, it may be necessary to cut the perineal tissue – a procedure called an episiotomy – to limit damage. This is a simple operation done under local anaesthetic. It should be performed only if there is a specific indication; these include:
to hasten the second stage of labour if the fetus is distressed.
to facilitate the use of forceps or vacuum extractor.
to enlarge a perineum that is restricted because of unyielding tissue, perhaps because due to a scar from a previous labour.
Midwives as well as obstetricians are trained to undertake and repair (with sutures) episiotomies.
Any previously existing mental-health problems may worsen under the stress of pregnancy and childbirth, and a woman's socio-economic circumstances may be an influential factor. Mood swings are common in pregnant women and mothers of new babies; sympathetic support from staff and relations will usually remedy the situation. If postnatal depression lasts for more than a week or two the use of mild ANTIDEPRESSANT DRUGS may be justified. If depression persists, referral to a psychiatrist may be advisable. Rarely, severe psychiatric problems – puerperal psychosis – may develop during or after pregnancy and referral to an appropriate psychiatric unit is then essential.