Aims and patterns of routine antenatal care

The concept that the general wellbeing and reproductive performance of a woman might be improved by antenatal supervision is surprisingly recent, and was first introduced in Edinburgh in 1911. In many societies, antenatal care is not available or, for social or religious reasons, is not used when it is available. Unfortunately, it is often least available in those communities where the need is greatest and where antenatal disorders, particularly those linked to malnutrition or over nutrition, are most common.

The basic aims of antenatal care are:

The ways by which these objectives are achieved will vary according to the initial health and history of the mother and are a combination of screening tests, educational and emotional support and monitoring of fetal growth and maternal health throughout the pregnancy.

The frequency of antenatal visits was first established by a group of providers of antenatal care in 1929. The protocol advised that antenatal visits should occur monthly from 8 weeks gestation until 28 weeks and then every 2 weeks until 36 weeks and thereafter weekly until the time of delivery. In modern antenatal care, the timing of visits, particularly in the first 28 weeks of pregnancy, is now more closely geared to attendance for screening tests. In uncomplicated pregnancy, a reduction in the number of visits has not been shown to adversely affect maternal or perinatal outcome, although maternal satisfaction may be reduced.

Antenatal care is provided through a variety of different mechanisms and may be provided by general practitioners, midwives and obstetricians, often in a pattern of shared care. Pregnancies that are considered to be high risk should receive a high proportion of their care by obstetricians or specialists in fetomaternal medicine. Risk stratification should be assessed at the earliest antenatal visits and care planned accordingly. Guidelines for consultation and referral, such as those produced by the Australian College of Midwives or by the National Institute for Health and Clinical Excellence (NICE), can be a useful tool to assess risk and determine the most suitable model of care. Pregnancy risk and the most suitable care provider may alter during the course of pregnancy.

Preconceptual care and vitamin supplementation

Ideally, all women would present prior to conception to allow their health care professional to provide them with prepregnancy care and counselling. This role is often best provided by the woman’s usual general practitioner. This appointment allows for an opportunity to undertake screening tests and provide advice regarding conception and early pregnancy care.

Essential components of preconceptual care include the assessment of the need for immunization for rubella, varicella and pertussis. If the history of past vaccination or infection is uncertain, serology may be required. If serology is negative or immunization is due, this can then be provided. As these vaccines are live attenuated viral vaccines, it is recommended that the woman use adequate contraception to defer conception for 28 days following administration. Administration of the influenza vaccine on a seasonal basis to women who are intending to be or who are pregnant is also recommended due to the increased incidence of serious morbidity associated with influenza infection in pregnancy. This visit is also an ideal opportunity to undertake routine cervical cytology (Papanicolou smear) if due.

Dietary and vitamin supplementation advice should also be given at this time. It is recommended that all women take a folic acid supplement (400 µg daily) for at least one month prior to conception and the first three months of pregnancy as an effective means of reducing the incidence of neural tube defects. Certain risk groups may be recommended to take a higher dose (5 mg daily) such as those on anti-epileptic agents, obese women, diabetic women or women with a past history of neural tube defects. Iodine supplementation of 150 µg per day is also recommended in countries or regions where there is a dietary deficiency of iodine to aid in the development of the fetal brain. Some countries have overcome the problem by using iodized salts for cooking.

Maternal medical conditions, including medications, can be reviewed and optimized at this time. This provides an opportunity to discuss the impact of pregnancy on the medical condition as well as the impact of the medical condition on pregnancy. Medication may need to be altered or doses reduced where appropriate. Referral to specialist physician colleagues for treatment optimization may be appropriate.

Optimization of preconceptional health with advice on a nutritious diet and regular moderate exercise should also be provided at this time. Exploration and discussion around the use of licit and illicit substances should also be explored.

Smoking has an adverse effect on fetal growth and development and is therefore contraindicated in pregnancy. The mechanisms for these effects are as follows (Fig. 7.1):

Changing demographics of pregnancy

Maternal age is an important determinant of outcome in obstetric services, with increased risk being associated with both extremes of maternal age. In recent years the median age of women giving birth in developed countries has continued to rise, and currently sits at around 30 years. The reasons for this are complex and due to a number of social, economic, and educational factors. Rates of pregnancy in the over 35 age group continue to rise (currently 23% of all births) as does that of women over 40 (4% of all births), however the number of mothers over 45 years remains low.

Access to assisted reproductive technologies (ART) has increased with a subsequent influence on median maternal age. Approximately 3.2% of babies born are conceptions assisted by ART in Australia and the UK. In addition, rates of multiple pregnancies continue to rise, currently around 1.6% of all mothers. This is largely due to the increases in ART and increasing maternal age. Rates of multiples in ART pregnancy are around 10% of all successful conceptions.

Rates of teenage pregnancy continue to decline and sit at around 4% of all births.

The absolute number of babies born to each woman continues to be low, with 75% of mothers giving birth to their first or second baby. The median age of first time mothers also continues to climb, and is currently around 28 years.

Women are active participants in antenatal care with over 98% having at least one antenatal visit and 92% having 5 or more visits. Preterm birth occurs in around 7.5% of all pregnancies, with most of these occurring in gestations greater than 32 weeks.

Around 75% of all women use analgesia in labour, most commonly nitrous oxide, followed by opioids, then regional techniques (predominantly epidural anaesthesia, around 30%). Rates in first time mothers of analgesic use are around 85%. Rates of caesarean section as a proportion of births increase with increasing maternal age.

The booking visit

The details of antenatal history and routine clinical examinations are discussed in Chapter 6. However, certain observations should be stressed at the first visit and it is preferable that these observations should be made within the first 10 weeks of pregnancy. The measurement of maternal height and weight is important and has value in prediction of pregnancy outcomes. Women with a low body mass index (BMI; less than 20, where BMI is estimated as weight (kg) divided by height (m²)) are at increased risk of fetal growth restriction and perinatal mortality. Women with a high BMI are increasingly recognized as being at increased antenatal and intrapartum risk, with the risks beginning to rise from a BMI of 30.

The initial measurement of blood pressure should be taken as soon as possible as this may provide evidence that, if there is hypertension, it is likely to have predated the pregnancy.

Consideration of past obstetric history, including mode of delivery

A record should be made of all previous pregnancies, including previous miscarriages and terminations, and the duration of gestation in each pregnancy. In particular, it is important to note any previous antenatal complications, details of induction of labour, the duration of labour, the presentation and the method of delivery, as well as the birth weight and gender of each infant. The mode of delivery (spontaneous, assisted or caesarean section) has implications for the current birth and needs to be explored. Previous operation records should be sought if relevant to aid in appropriate counselling for this pregnancy.

The condition of each infant at birth and the need for care in a special care baby unit should be noted.

Complications of the puerperium such as postpartum haemorrhage, extensive perineal trauma or wound breakdown, infections of the genital tract, deep vein thrombosis or difficulties with breastfeeding may all be relevant to the current pregnancy.

Recommended routine screening tests

Beginning at the first visit, a number of screening tests are introduced. Some will be repeated later in the pregnancy. The omission of these tests will generally now be considered to be evidence of substandard practice so they have medicolegal importance as well as clinical relevance.