Chapter 6 Antenatal care
AIMS OF ANTENATAL CARE
The aims of antenatal care are to ensure that:
PRECONCEPTION ADVICE
Ideally all women planning to become pregnant should be seen before conception. This visit gives the opportunity to review her personal and family history and to optimize control of conditions, such as hypertension or diabetes, before pregnancy.
It is also an opportunity to outline her antenatal care options and to discuss the tests she will be offered during the pregnancy, for example, screening for chromosome anomalies. If there is a history of congenital or genetic abnormalities referral to a genetics clinic can be arranged. If the woman is overweight or underweight she can be given appropriate dietary and exercise advice and be offered referral to a dietitian. The immune status of the woman can also be explored, particularly relating to her ABO group and Rhesus factor, and immunity to rubella, hepatitis B and C and varicella.
All women should be advised to take 0.4 mg of folate in the weeks before becoming pregnant and for the first 3 months of pregnancy to reduce the risk of a neural tube defect. Women with a past history of spina bifida or anencephaly should increase their daily intake of folate to 4 mg/day. Women who smoke should be strongly encouraged and supported to quit, for the reasons detailed later. If her partner also smokes he should also be encouraged to access a QUIT programme.
ANTENATAL CARE PROVIDERS
The providers of antenatal care may be a general practitioner, an obstetrician or a midwife. In many centres antenatal care is now provided by a team comprising midwives, hospital-based obstetricians and community general practitioners, each member of the team contributing their particular skills and expertise. The antenatal care may take place in a doctor’s rooms, in a hospital clinic, or in a clinic conducted by a midwife. The opportunity should be available for an expectant mother to choose which facility she would prefer, but she should know that, if a complication should arise, she would be transferred, if necessary, quickly and efficiently, to a facility staffed by experienced obstetricians.
Whichever facility a pregnant woman has chosen she should have the opportunity to talk to a health professional about matters that concern her during the pregnancy in an unhurried way and have her questions answered by an informed, communicative doctor and midwife.
PSYCHOLOGICAL PREPARATION FOR MOTHERHOOD
Some women appear confident that their pregnancy will proceed normally and that the birth of the baby will be easy. Most women, however, have concerns about the pregnancy and the process of childbirth. In the early weeks many women fear that the pregnancy may terminate as a miscarriage. Later in pregnancy many women fear that the baby will be malformed or retarded, or that childbirth will be dangerous and painful. A few women are concerned that after the birth they will not be able to regain their prepregnancy body shape. These fears may not be expressed unless the woman feels confident that she is able to ask her doctor about them and expect to receive a reasoned answer. Fears about the difficulty and pain of childbirth can be reduced by simple explanations of the nature and course of labour.
Women who obtain social and psychological support during pregnancy are less likely than those who do not, to have negative feelings about their pregnancy and the forthcoming birth. They are more likely to feel that they are ‘in control’ during the pregnancy, to have a worry-free childbirth, to communicate more effectively with their doctor or nursing staff, and to be more satisfied with the care they receive.
Many women are helped by antenatal classes, run either in conjunction with antenatal clinics or privately. The importance of providing written information in the woman’s primary language cannot be overstated.
DIET IN PREGNANCY
Many pregnant women are confused about what they should eat during pregnancy to make sure that they and their baby are properly nourished. What should a pregnant woman eat? To a large extent this will depend on her cultural background, her usual eating behaviour and her income level. As a general principle, women should be advised to eat a well-balanced diet that includes a sufficient amount of each of the five core food groups. It should be low in fat and high in fibre, with sufficient fresh fruit and vegetables, as is suitable for the general population and for her family. Although many women will eat slightly more during pregnancy there is no good evidence that they should drastically alter or increase their food intake. Table 6.1 shows the mean daily intake or RDI (recommended daily intake) that women should try to achieve. Table 6.2 shows what a pregnant woman should try to eat each day, translated into the foods a household buys.
Table 6.1 Recommended daily intakes
| RDA | See Note | |
|---|---|---|
| Protein | 51 g | * |
| Thiamin | 1.0 mg | * |
| Riboflavin | 1.5 mg | * |
| Niacin | 14–16 mg niacin equivalents | * |
| Vitamin B6 | 1.0–1.5 mg | * |
| Total folate | 400 μg | † |
| Vitamin B12 | 3.0 μg | * |
| Vitamin C | 60 mg | * |
| Zinc | 16 mg | * |
| Iron | 32–36 mg | ‡ |
| Iodine | 150 μg | * |
| Magnesium | 300 μg | * |
| Calcium | 1100 μg | * |
| Phosphorus | 1200 μg | * |
| Selenium | 80 μg | * |
| Vitamin A | 750 μg retinal equivalents | |
| Vitamin E | 7.0 mg α-tocopheral equivalents | |
| Sodium | 920–2300 mg | |
| Potassium | 1950–5460 mg |
* Indicates an increased requirement compared to non-pregnant female 19–54 years
† Daily requirement is doubled to 400 μg daily. RDI = 200 μg in a non-pregnant female 19–54 years
‡ RDI is expressed as a range to account for differences in bioavailability in foods. RDI is for second and third trimesters
| Carbohydrate foods | = | 4–6 servings |
| 1 serving | = | 2 slices bread |
| = | 1 cup cooked rice, pasta, noodles | |
| = | 1 cup porridge or 1⅓ cup cereal flakes | |
| Protein foods | = | 1½ servings |
| 1 serving | = | 100 g cooked meat or chicken |
| = | ½ cup cooked dried beans or peas | |
| = | 2 small eggs | |
| = | 120 g fish fillet or ½ cup tinned fish | |
| = | ⅓ cup nuts | |
| Milk and dairy foods | = | 3 servings |
| 1 serving | = | 250 mL or 1 cup of milk |
| = | 40 g or 2 slices cheese | |
| = | 1 carton/200 g yoghurt | |
| Fruit | = | 4 servings |
| 1 serving | = | 1 piece of fruit |
| = | ½ cup juice | |
| = | 1 cup canned fruit | |
| Vegetables | = | 5–6 servings |
| 1 serving | = | ½ cup cooked vegetables |
| = | 1 cup salad vegetables | |
| = | 1 potato | |
| = | ½ cup cooked dried beans/lentils | |
| Extras | = | 0–2½ servings |
| 1 serving | = | ½ chocolate bar |
| = | 1 slice cake | |
| = | 1 packet chips (crisps) |
Most pregnant women who eat a sensible diet do not need vitamin supplements, with the exception of folate. It is now recommended that a woman who intends to become pregnant should take folate 0.5 mg a day for 3 months prior to conception and during the first trimester. Generally high-folate foods should be encouraged, such as plenty of fresh fruit and vegetables, and fortified breakfast cereals, as well as a folic acid supplement, as it is generally difficult to obtain this extra folate without a supplement. Women carrying a multiple pregnancy should continue taking folate throughout.
Healthy women living in the industrialized countries whose haemoglobin is within the normal range and who eat a sensible diet usually do not require iron supplements. However, many women routinely supplement their diet with iron, as they may find it difficult to eat enough iron-rich foods and are at risk of iron deficiency. A protective factor in pregnancy is that dietary iron absorption is also increased. Iron-rich foods, such as red meat, legumes/pulses, wholegrain breads and cereals and fortified breakfast cereals, should be encouraged as well as including vitamin C-rich foods with those foods containing iron to aid in the absorption of iron. High-risk women in developed countries, such as: women on a limited budget; women with fad food behaviours or eating disorders; vegan/vegetarian women; and most women living in the developing countries require iron supplementation. This is discussed in Chapter 15.
Calcium requirements are increased from 800 to 1100 mg calcium per day. This is usually met quite easily by an intake of three servings of calcium-rich foods daily. As with iron, the absorption of calcium from the diet is increased during pregnancy. Occasionally a woman may choose or be prescribed additional calcium.
Vitamin D stores may be inadequate in women who have restricted exposure to sunlight, who have a diet low in oily fish, eggs and meat or who are obese. These women should be advised to take 10 μg of vitamin D daily.
Another important food issue in pregnancy is for women to practise good food hygiene and food safety. This includes basic advice such as storing, preparing and cooking foods at the appropriate temperatures, and avoiding foods that may not be cooked thoroughly, i.e. foods from takeaway shops, meat pies and salads. The avoidance of uncooked foods such as soft cheese and raw fish is also prudent. The rationale for this is to ensure that all food is uncontaminated by food-borne bacteria, particularly Listeria, which may be harmful for the fetus.
ANTENATAL SCREENING
A great deal of prenatal care is spent in detecting potentially dangerous conditions early; screening is one strategy used. In its simplest form blood pressure measurement is a screening strategy, and is discussed later. Currently, much interest is being shown in screening for congenital defects, such as Down syndrome, neural tube defects and single gene defects, using DNA probes (Box 6.1).
Box 6.1 Possible indications for genetic diagnostic tests in first half of pregnancy
Screening for genetic defects
Screening for Down syndrome and certain other genetic defects (for example cystic fibrosis, thalassaemia, haemophilia, Huntington’s disease, some muscular dystrophies) can be carried out by chorionic villus sampling or amniocentesis. Before using these methods, an ultrasound examination of the fetus is made to exclude gross abnormalities (Figs 6.1–6.3).
Fig. 6.2 The scan shows an empty amniotic sac at 11 weeks’ gestation. The patient aborted 1 week later.
Fig. 6.3 Scan of a normally developing fetus at 12 weeks’ gestation. The measurement of nuchal thickness is within the normal range, indicating a very low risk of Down syndrome.
Chorionic villus sampling
A sample of chorionic tissue is removed from the placental edge between the 9th and 11th weeks of pregnancy by introducing a needle transabdominally and advancing it to the edge of the placenta under ultrasound guidance. About 20 mg of chorionic tissue is sucked into a syringe. The karyotype of the sample is determined within 48 hours.
Amniocentesis
The procedure is carried out at about the 15th week of pregnancy. A needle is thrust through the abdominal wall and into the amniotic sac, guided by ultrasound to avoid the placenta and fetus, and a sample of amniotic fluid is removed. This is centrifuged and the fetal cells obtained are cultured for 3 weeks. They are then harvested and a karyotype is made.
Chorionic villus sampling or amniocentesis?
The choice between chorionic villus sampling (CVS) and amniocentesis is controversial. CVS is performed in the first quarter of pregnancy and a preliminary karyotype result using FISH is obtained within 24–48 hours, so that parental anxiety about the result is reduced. However, the karyotyping is slightly less accurate than with amniocentesis because of potential contamination with cells of maternal origin, and the risk of abortion following CVS is slightly higher (1–3% above the background rate compared with 0.5–1% following amniocentesis). Concern has been expressed that CVS may be followed in late pregnancy by oligohydramnios and limb defects. A multicentre study of over 140 000 patients has shown no increase in these defects when CVS is compared to amniocentesis. On the other hand, the karyotype is only obtained 2 weeks after amniocentesis, which increases the psychological stress on the parents, and if the fetus is abnormal and termination of pregnancy is suggested, the process is more painful and psychologically disturbing.
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