Routine antenatal care

Introduction

Antenatal care is a key component of a healthy pregnancy. Regular antenatal care helps to identify and treat complications and to promote healthy behaviours. Although there is little direct evidence, outcome data suggest that neonates born to mothers who do not receive antenatal care are 3 times more likely to be of low birth weight, and 5 times more likely to die, compared with neonates born to mothers who receive antenatal care. [US Department of Health and Human Services: prenatal services] In addition to medical care, antenatal care includes counselling and education. This monograph provides an overview for the antenatal management of healthy pregnant women with singleton pregnancies.

Pre-conception care

Ideally, antenatal care begins before conception. Pre-conception care has been defined as a set of interventions to identify and modify biomedical, behavioural, and psychosocial risks to a woman's health or pregnancy outcome through prevention and management. Pre-conception care should be considered not as a single visit, but as a continuum of care throughout a woman's reproductive life. [1] Because a significant proportion of pregnancies are unintended, the negative consequences of many behaviours, illnesses, and medications can affect fetal development early in pregnancy; often damage to the fetus occurs before a woman even realises that she is pregnant. Thus, all routine healthcare encounters during a woman's reproductive years should include counselling on medical care and healthy behaviours to optimise pregnancy outcome. [1] [2] For example, healthy women should begin folic acid supplementation (400 micrograms/day), ideally at least 3 months before conception and continue until 12 weeks' gestation. [1] [3] [4]

Factors affecting pregnancy outcome should include consideration of family history, genetic history, nutritional status, folic acid intake, environmental and occupational exposures, and teratogens. A history of illicit-substance use, tobacco and alcohol consumption, medical conditions, medication, immunisation status, risk factors for STDs, psychosocial concerns (depression, domestic violence), and pregnancy spacing is required. For example, women with diabetes should be counselled on optimising glycaemic control, and pregnancy should be discouraged until control is achieved. [International Diabetes Federation: global guideline on pregnancy and diabetes]

Immunisations for rubella, varicella, or hepatitis B should be offered to women who are susceptible, and women should avoid pregnancy for 1 month after receiving a live attenuated vaccine (e.g., rubella or varicella), even though the evidence does not suggest that they are in fact harmful. [5] [6] [CDC: guidelines for vaccinating pregnant women] Recommendations are also available on vaccination for pertussis, tetanus, and diphtheria (Tdap) during pregnancy and postpartum. [7]

Antenatal care

Early and regular antenatal care is recommended to improve pregnancy outcomes. Recommendations include antenatal visits, nutritional care, education, and other patient-specific issues.

Antenatal visits

• Traditional antenatal care includes a series of between 7 and 11 visits; however, the number of visits necessary for adequate care is disputed. Though limited data are available regarding the optimal frequency, timing, and content of visits, the number of prenatal care visits should be determined according to the needs and risk status of each woman and her fetus. In addition to scheduled routine visits, pregnant women should have access to unscheduled or emergency visits on a 24-hour basis. In the UK, 10 visits for an uncomplicated nulliparous woman and 7 for an uncomplicated parous woman are recommended. [8]

• It is recommended that pregnant women initiate antenatal care by 10 to 12 weeks' gestational age. [9] The first prenatal visit should include a comprehensive history, laboratory work, and education about pregnancy health. Height and weight should be recorded to calculate BMI, which provides information to determine weight gain guidelines. Structured records assist in ensuring comprehensive, evidence-based care. [10]

• A comprehensive physical examination should be performed at the first or second visit.

• At the second visit, a review of laboratory results will promote further discussion of a management plan.

• An initial exam will identify women with female genital mutilation (FGM). Because FGM may adversely affect birth outcomes and increase risk for obstetric complications, [11] [12] these patients may have special intrapartum care needs.

• Antenatal care visits should be scheduled at appropriate intervals to ensure time-sensitive testing and screenings, administration of anti-D immunoglobulin if needed, and monitoring for common complications.

• Typical frequency of visits in an uncomplicated pregnancy:

  • Every 4 weeks for the first 28 weeks

  • Every 2 to 3 weeks between 28 and 36 weeks

  • Weekly after 36 weeks.

• More frequent visits may occur at the antenatal care provider's discretion or at a patient’s request. Although no evidence-based guidelines on content of visits are available, typical visits include evaluation of BP, weight, testing urine for protein levels, and checking the fetal heart rate.

• In areas with limited resources, reduced-visit programs are associated with an increase in perinatal mortality compared to standard practice, although neonatal intensive care admissions may be reduced. While fewer visits may be associated with lower costs, a standard visit schedule should be recommended to all patients. [13]

• Screening for depression, which is common during pregnancy and the postpartum period, may be beneficial, particularly in women with a history of major depression. Undiagnosed and untreated psychiatric illness is a risk to both the mother and fetus. [14] [15]

• Psychosocial screening to ascertain any existing anxiety, depression and other aspects (e.g. evidence of domestic abuse) should be considered. The American College of Obstetricians and Gynecologists (ACOG) also recommends performing psychosocial screening at least once each trimester to identify issues that may require further evaluation, intervention, or outside referral. [16]

• Appropriate fetal growth can be screened by measuring fundal height (symphysis to uterine fundus) from 20 weeks' gestation, although most studies suggest that the sensitivity of fundal height as a measurement of growth restiction is <50%. Fundal height in centimetres is approximately equal to the gestation age in weeks. Discrepancies of >3 cm should prompt ultrasound evaluation of amniotic fluid index and fetal growth. The antenatal care provider should keep in mind that fundal height measurements can be influenced by numerous factors, including maternal size, bladder filling, uterine fibroids, multiple gestations, and fetal presentation. [8] [17] [18]

• Expectant mothers are questioned regarding pain, fetal movement, contraction frequency, vaginal bleeding, loss of fluid or discharge, other symptoms of preterm labour, and preeclampsia symptoms at appropriate gestation intervals, in addition to any other patient-provided complaints or concerns.

• Screening can successfully identify depression during pregnancy. This enables the recognition of patients that may benefit from targeted therapy.

Nutritional counselling

• Nutrition education should focus on a well-balanced, varied, nutritional food plan consistent with the patient's food preferences. Using BMI as a guideline, appropriate weight gain should be discussed. [19] [Institute of Medicine: weight gain during pregnancy: reexamining the guidelines]

  Weight gain during pregnancyAdapted from Institute of Medicine. Weight gain during pregnancy: re-examining the guidelines. 2009 Obese women should be counselled on healthy eating, and encouraged to participate in physical activity which will support weight management during and after pregnancy. [20] [NICE: dietary interventions and physical activity interventions for weight management before, during and after pregnancy]

• The Royal College of Obstetricians and Gynaecologists (RCOG) recommends supplementation of vitamin D in women at risk of deficiency; however, more research is required to establish appropriate dosing. [21]

• A nutrition consultation should be offered to all obese women. Typical recommendations for caloric intake are estimated using 25 to 35 kcal/kg of optimal body weight with an additional 100 to 200 kcal per day during pregnancy. [2]

• Weight gain and caloric intake recommendations are higher for women pregnant with twins or higher-order multiple gestations. The daily recommended caloric intake for women with a normal BMI, who are pregnant with twins, is 40-45 kcal/kg daily. [22] Additional iron, folate, calcium, magnesium, and zinc supplementation may also be required for patients carrying multiple gestations over routine prenatal vitamin intake.

• Fish intake should be no more than 340 g (12 ounces) per week of fish or shellfish low in mercury content. [FDA: what you need to know about mercury in fish and shellfish - March 2004]

• Listeriosis is a bacterial illness that can be particularly harmful to pregnant women, possibly resulting in miscarriage or stillbirth. To prevent listeriosis, pregnant women should avoid unpasteurised milk, soft cheeses, raw or undercooked meat, poultry, and shellfish, and any uncooked or undercooked ready-prepared meals. Additionally, pregnant women can reduce their risk of Salmonella infection by avoiding raw or partially cooked eggs or food that may contain them (e.g., mayonnaise) and raw or partially cooked meat, especially poultry. [2] [8]

• Daily prenatal vitamins containing folate (400 micrograms per day) are recommended as tolerated throughout pregnancy, and at least through the first 3 months of pregnancy. Ideally, women should start folate supplementation 12 weeks prior to conception. Selected presentations, such as a prior pregnancy complicated by fetal neural tube defect, require higher-dose folate intake of 4 milligrams per day.

• While observational data suggest that omega-3 fatty acid docosahexaeonic acid (DHA) supplementation has a beneficial effect on paediatric neurodevelopmental outcomes, randomised controlled trials have yielded conflicting results. At present, there is insufficient evidence to support DHA supplementation to prevent preterm birth. [23] There is also no evidence that such supplementation reduces the risk of preeclampsia or gestational diabetes mellitus. [24]

• Vitmain C and E supplementation during pregnancy does not prevent preeclampsia. [25]

• Moderate caffeine intake does not appear to have negative effects on pregnancy; however, caffeine intake should be limited to <200 mg daily. [26]

Education

• Education to promote maternal and fetal health and safety is a significant component of antenatal care. Topics that should be discussed at first antenatal visit include promotion of healthy behaviours, dental care, [Oregon Oral Health Coalition: guidelines for oral health care in pregnancy] nutrition, wearing a seat belt, continued exercise, avoiding substance and hazardous-chemical exposure, and minimal use of hot tubs or saunas or potential domestic violence exposure. Sexual activity may also be discussed. [Maternal and Child Health Bureau: a healthy start: begin before baby's born] If women use tobacco products, smoking cessation should be encouraged and support provided. [27] [NICE: how to stop smoking in pregnancy and following childbirth] If the patient has had a prior caesarean delivery, the risks and benefits of a trial of labour versus repeat caesarean delivery should be reviewed. [2]

• Alcohol consumption is contraindicated in pregnancy. Antenatal drinking poses potentially serious consequences to both mother and fetus. Brief standardised screening questionnaires (T-ACE, AUDIT-C, TWEAK) show promise as screening tools to identify risk drinking in pregnant women, although further investigation is required. [28]

• Specific issues to consider: [9] [29]

  • Breastfeeding: throughout antenatal care, healthcare providers should provide information about the benefits of breastfeeding and breastfeeding support should be provided. [30]

  • Working: most women with an uncomplicated pregnancy can typically continue working until the onset of labour. However, if women have medical complications or other pregnancy complications, or the occupation involves physical work, prolonged standing, or significant stress, some adjustments may need to be made.

  • Air travel: women with uncomplicated pregnancies can fly safely until 36 weeks' gestation. Pregnant women who are planning to fly should be informed about the increased risks of venous thromboembolism from the combination of pregnancy and venous stasis, and instructed to take appropriate precautions (support stockings, movement of lower extremities, hydration). [31] [32]

  • Exercise: women should be encouraged to continue or begin a moderate aerobic exercise program during pregnancy. [NICE: dietary interventions and physical activity interventions for weight management before, during and after pregnancy] Although the limited available RCT data do not clearly support a benefit of exercise during pregnancy for the prevention of glucose intolerance or gestational diabetes mellitus, [33] there may be other physical and psychological benefits derived from aerobic exercise in pregnancy. Potential risks from contact sports, high-impact sports, activities with risk of abdominal trauma, and scuba diving should also be discussed.

  • Childbirth education: attendance in childbirth education classes should be encouraged. Classes teach expectant mothers about labour and delivery, pain relief options, potential obstetric complications and procedures, normal newborn care, and postpartum adjustment. Supportive information should be provided regarding the benefits of breastfeeding.

  • Miscellaneous: other educational issues to discuss during the antepartum period include postpartum contraception and circumcision of male infants.

Routine testing

All patients should be advised to have an FBC, blood type, urinary glucose measurement, urine dipstick and culture, Rhesus and rubella status, with review of last cervical screening. Screening for STDs should be considered (to include syphilis, hepatitis B, HIV infection, gonorrhoea, and chlamydia). [34] All expectant mothers should be offered ultrasound. Other investigations may be performed as indicated.

Recommended routine testingFrom the collection of Dr ME D'Alton and Dr RS Miller

Routine screening for bacterial vaginosis in asymptomatic women and women not at risk for preterm delivery is not recommended. [Society of Obstetricians and Gynaecologists of Canada: screening and management of bacterial vaginosis in pregnancy]

Additional tests to consider

Some public health departments require additional testing (e.g., more frequent syphilis screening). In addition to routine laboratory tests, several other screening tests should also be considered, many of which are based on racial and ethnic background or family history.

STDs

• Patients living in areas with high rates of STDs, or those patients with previous antepartum STD infection, should be considered for repeat STD testing in the third trimester.

Vitamin D

• Screening for vitamin D deficiency during pregnancy has been advocated by some, [35] particularly for at-risk women, including women with dark skin, those who live in northern latitudes, and women whose clothing leaves little skin exposed. However, it remains controversial because other experts, including the American College of Obstetricians and Gynecologists (ACOG), believe existing data are insufficient to offer specific guidelines, especially regarding safety and efficacy of supplementation. [36] However, when deficiency is identified during pregnancy, supplementation with 1000-2000 units/day of vitamin D is considered to be safe. [36] The Institute of Medicine has published a report on the dietary reference intakes for calcium and vitamin D advising an Estimated Average Requirement (EAR) for vitamin D of 400 IU/day (10 micrograms/day) with a Recommended Daily Allowance (RDA) of 600 IU/day (15 micrograms/day) during pregnancy. [37]

TFTs

• Universal screening for subclinical hypothyroidism is controversial. Although several major societies favour routine screening in women who are pregnant or planning pregnancy, [38] ACOG maintains that data are insufficient to warrant routine screening and continues to recommend testing in symptomatic women and those with a personal history of thyroid disease or other medical conditions associated with thyroid disease. [39] [40] To date, evidence does not support treatment of subclinical hypothyroidism as an intervention to improve pregnancy outcome. [41] [39] [40]

Haemoglobinopathies

• Patients at increased risk for carrying haemoglobinopathies (e.g., sickle cell anaemia or thalassaemia) should be offered haemoglobin electrophoresis. [42] [43] Haemoglobinopathies are more common in families of African, African American, Southeast Asian, and Mediterranean descent. If the mother is a carrier of a clinically significant haemoglobinopathy, the father should also be offered screening. If both parents are carriers, genetic counselling should be offered to enable them to make informed decisions regarding the pregnancy. [42]

Genetic screening

Carrier status for other diseases should also be considered and testing offered. Examples include:

• Haemochromatosis: people of Celtic ancestry (especially if a positive Fhx exists)

• Cystic fibrosis: although there is a higher frequency of cystic fibrosis in white people of European descent and in the Ashkenazi (Eastern European heritage) Jewish population, the option of cystic fibrosis carrier screening should be recommended and made available to all patients.

• Tay-Sachs disease: Ashkenazi Jews, French Canadians, Cajuns

• Panels are available that detect mutations associated with 8 disorders that commonly occur in Ashkenazi Jewish populations: Bloom syndrome, Canavan disease, cystic fibrosis, familial dysautonomia, Fanconi anemia group C, Gaucher disease, Niemann-Pick diseases (types A and B), and Tay-Sachs disease.

Additional testing can be considered depending upon familial history, or on patient and physician preference:

• Fragile X syndrome [44]

• Spinal muscular atrophy

• Duchenne's muscular dystrophy.

Ultrasonography

First trimester ultrasound screening is optimal for pregnancy dating; however, a complete anatomic evaluation cannot be performed at this time. If size-date discrepancy is present upon initial examination, or if menstrual dates are uncertain, an ultrasound examination is indicated for accurate dating. An ultrasound performed for first-trimester aneuploidy screening will also provide accurate dating information. [45]

An ultrasound examination performed between 18 and 22 weeks is optimal for a survey of the fetal anatomy and placental location. It can also confirm pregnancy dating if an earlier ultrasound was not performed. The sensitivity of ultrasound to detect fetal anomalies ranges from 13% to 82%, depending on the type of anomaly, the level of risk in the population, and the expertise of the operators. Additional ultrasound examinations are not necessary unless maternal or fetal indications are present. Women should be informed of the limitations of routine ultrasound. [9] [45] [46] Ultrasonography in pregnancy is not associated with adverse maternal, perinatal, or childhood outcomes. [47] Long-term follow-up data from a randomised controlled trial found no significant effect of second-trimester ultrasound exposure on overall school performance in teenagers. [48] Obese patients should be informed that their fetus is at increased risk for congenital anomalies, including undiagnosed anomalies. [49] Sonographic fetal anatomical assessment may be better performed at 20 to 22 weeks in obese patients.

Routine second trimester ultrasound examination will reveal placental location and relationship to the internal cervical os. Placenta praevia complicates 0.3% to 0.5% of pregnancies. The majority (>90%) of praevia cases diagnosed at 20 weeks resolve by term. Thus, a follow-up ultrasound in the third trimester, usually between 32 and 35 weeks, is warranted, as this information may influence delivery planning. [8] [45] [50] [51] [Finnish Medical Society Duodecim: ultrasound scanning during pregnancy]

Screening for chromosomal abnormalities

Aneuploidy

• Defined as an abnormal number of chromosomes, with 46 chromosomes representing normal in humans.

• There may be fewer chromosomes, as in Turner's syndrome (monosomy X) , or more chromosomes, as in Down's syndrome (trisomy 21).

• Chromosomal abnormalities occur in 1:160 live births, with trisomy 21 (Down's syndrome), trisomy 18, and trisomy 13 accounting for the majority. Trisomy 18 and trisomy 13 are often incompatible with survival. [52]

• Although the frequency of aneuploidies increases with advancing maternal age, they can present at any age (most children with Down's syndrome are actually born to women younger than 35 years of age). The American College of Obstetricians and Gynecologists (ACOG) recommends that all women, regardless of age, who present for antenatal care before 20 weeks should be offered aneuploidy screening. [53] Women should be counselled on the age-related risk of fetal aneuploidy, the implications of a diagnosis, and all available screening tests, including their advantages and disadvantages. In addition, all women should have the option of invasive prenatal screening (chorionic villus sampling [CVS] or amniocentesis) for diagnosis of fetal aneuploidy.

Screening tests for aneuploidy

• A variety of screening tests are available, incorporating maternal age, ultrasound, and biochemical markers.

• First-trimester screening may be performed from 11 to 13 weeks' gestational age and includes ultrasound evaluation for nuchal translucency thickness plus maternal serum screening (pregnancy-associated plasma protein A, human chorionic gonadotropin). The detection rate for Down's syndrome, at a positive screening rate of 5%, ranges from 82% to 90%. [52] [53] [54] Adding evaluation of the nasal bone, which is absent in 60% to 70% of fetuses with Down's syndrome, can increase the detection rate to 95%. Technical standards and guidelines are available. [55]

• Second-trimester screening includes a maternal quadruple marker screening (human chorionic gonadotropin, alpha-fetoprotein, oestriol, and inhibin), with a detection rate for Down's syndrome of 81%. [53] [52]

• Combining screening results from both first- and second-trimester screening tests (i.e., integrated and sequential screening) can improve aneuploidy detection rates. [53] [52]

• It is important to be aware that when maternal serum is screened for the usual clinical indications (i.e., aneuploidy and neural tube defect), abnormal analyte results may also identify pregnancies at risk for adverse outcomes, such as preeclampsia, and these women should be referred for appropriate follow-up or consultation. [56]

• Non-invasive antenatal aneuploidy screening for trisomies 21, 18, and 13 using cell-free fetal DNA is an option that has recently become available to women with pregnancies at increased risk of aneuploidy. [57] The test may be offered to appropriately counselled patients but should not be a component of routine antenatal laboratory studies. Cell-free fetal DNA screening has been validated in high-risk patient populations, but further study in low-risk populations and multiple gestations is required prior to widespread application. Importantly, as this is a screening study and not a diagnostic test, negative results cannot entirely exclude the possibility for aneuploidy and positive results should be confirmed with invasive genetic testing.

• Ultrasound: second-trimester ultrasound can be used to detect fetal anatomical markers associated with aneuploidy that may modify a pregnancy’s risk of carrying an affected fetus. Examples of these sonographic markers include an echogenic intracardiac focus, absent nasal bone, short humerus or femur, echogenic bowel, 2-vessel umbilical cord, and sandal-gap toe deformity. [45] [52] [53]

• Whichever screening test is used, the patient should be advised that screening provides an individual risk assessment, but it is not diagnostic.

Invasive testing [58]

• Invasive testing is necessary to definitively diagnose chromosomal abnormalities.

• All women with a positive screening test (risk of Down's syndrome greater than or equal to the risk for a 35-year-old woman or 1:270) should be offered genetic counselling and diagnostic testing.

• Options for invasive genetic testing include CVS (at 10-12 weeks) and diagnostic amniocentesis (at ≥15 weeks). Patient counselling requires a discussion regarding the risks and benefits of each procedure, and a comparison of the relative merits and disadvantages between procedures.

• Any discussion of invasive testing options must include disclosure that the procedure may cause obstetrical complications such as pregnancy loss or preterm rupture of membranes.

Some women may choose to bypass screening and proceed directly to diagnostic testing. [53] The option of invasive genetic testing should be available to all patients regardless of prior aneuploidy risk level.

Screening for neural tube defects (NTDs)

There are 2 approaches for NTD screening:

1. Maternal serum alpha-fetoprotein (MS-AFP) in the second trimester (15 to 22 weeks' gestation, optimal at 16 to 18 weeks)

2. Ultrasound.

MS-AFP has historically been used as a screening test: the standard screening cut-off, of 2.5 multiples of the median, detects about 80% of cases of open spina bifida and 90% of cases of anencephaly. If women screen positive, a detailed ultrasound is performed:

• To ensure that the pregnancy is viable and accurately dated

• To evaluate for the presence of multiple gestations

• To assess fetal anatomy for NTDs and other defects associated with an elevated MS-AFP (omphalocoele, gastroschisis, cystic hygroma). [2]

Amniocentesis can be performed to determine if amniotic fluid AFP is elevated and acetylcholinesterase is present, which are considered diagnostic of a NTD. [2] [59] [60]

At present ultrasound is favoured over MS-AFP as a screening tool although these 2 screening modalities are not mutually exclusive. With experienced sonographers, the detection rate of NTDs approaches 95% to 100%. [59] [60]

Screening for gestational diabetes mellitus (GDM)

National Institute for Health and Clinical Excellence (NICE) together with US Preventive Services Task Force (USPSTF) recommends screening only for high-risk women: [60] [61]

• BMI (kg/m^2) >30

• Age >25 years

• Diabetes in a first-degree relative

• A personal history of abnormal glucose tolerance

• Member of an ethnic group with high diabetes prevalence (Hispanic, Native American, South or East Asian, African, or Pacific Islands ancestry)

• History of an adverse obstetric outcome usually associated with GDM.

The International Diabetes Federation (IDF) advises that women at high risk of diabetes due to previous GDM should be offered screening as soon as practical and, if normal, repeat screening at 26 to 28 weeks. The IDF advises that all other women should be offered testing at 26 to 28 weeks. [International Diabetes Federation: global guideline on pregnancy and diabetes]

NICE guidance recommends a one-step 75 g oral glucose tolerance test (OGTT), but does not recommend undertaking a fasting plasma glucose, and uses the World Health Organization definition of GDM with plasma glucose values exceeding: [62]

• 2 hours ≥7.8 nmol/L

The International Association of Diabetes and Pregnancy Study Groups Consensus Panel and American Diabetes Association also recommend a one-step 75 g OGTT for all women not already known to be diabetic at 24 to 28 weeks of gestation. [63] [64] Women with risk factors should be screened at the first antenatal visit, using standard diagnostic criteria. [64]

• At 24 to 28 weeks of gestation in all women not previously diagnosed with overt diabetes, perform a 75 g OGTT, with plasma glucose measurement fasting at 1 and 2 hours.

• The OGTT should be performed in the morning after an overnight fast of at least 8 hours.

• The diagnosis of GDM is made when any of the following plasma glucose values are exceeded:

  • Fasting ≥5.1 mmol/L (92 mg/dL)

  • 1 hour ≥10.0 mmol/L (180 mg/dL)

  • 2 hours ≥8.5 mmol/L (153 mg/dL).

The ACOG Committee on Obstetric Practice recommends a 2-step approach to laboratory screening and diagnosis, with the screening step to be performed at 24 to 28 weeks of gestation. This consists of a 50 g, 1-hour screening test, followed by a 100 g, 3-hour oral glucose tolerance test (OGTT) if needed for definitive diagnosis. [65] The ACOG does not recommend a 1-step OGTT, owing to concern that this practice would increase the incidence of a diagnosis of GDM and resultant healthcare costs without evidence to support an improvement in maternal or newborn outcomes. [65]

Screening for group B Streptococcus (GBS)

In the UK screening for group B Streptococcus (GBS), colonisation is not performed routinely. Elsewhere, screening may be offered. For example, in the US, all pregnant women are offered screening for vaginal-rectal GBS colonisation at 35 to 37 weeks' gestation. [17] Intravenous antibiotics should be given to all pregnant women identified as GBS carriers at the time of labour or rupture of membranes. Colonisation during a previous pregnancy is not an indication for intrapartum prophylaxis in a subsequent pregnancy. Women with GBS isolated from the urine in any concentration during pregnancy or who have a previous infant with GBS infection should also receive intrapartum prophylaxis. [66] For patients presenting with unknown GBS colonisation status, anticipated premature delivery <37 weeks, rupture of membranes >18 hours prior to delivery, and maternal temperature of 37.7°C (100.4°F) or greater without evidence of chorioamnionitis are considered reasons to initiate intrapartum prophylaxis.

Rho D immune globulin administration

Rh-negative women should receive Rho D immune globulin if they have any of the following: [2]

• An ectopic pregnancy

• Miscarriage or termination of pregnancy

• Any invasive procedures (amniocentesis, chorionic villus sampling)

• Possibility of fetal-maternal haemorrhage (abdominal trauma, placental abruption)

• If they deliver a neonate who is Rh-positive.

Rh-negative women should be given Rho D immune globulin at 28 weeks' gestation. The patient may decline administration if paternity is certain, and the father of the neonate is known to be Rh-negative. [2] [8] [67]

Diagnosis and treatment of anaemia in pregnancy

Anaemia in pregnancy has been defined as Hb levels <110 g/L (<11 g/dL) and Hct levels <33% in the first and third trimester, and Hb levels <105 g/L (<10.5 g/dL) and Hct levels <32% in the second trimester. [68] Because racial differences exist, it has been suggested that Hb cut-off levels for black women should be lowered by 8 g/L (0.8 g/dL). [69] However, in pregnancy, there is no evidence that Hb concentrations <95 g/L (<9.5 g/dL) are harmful to either mother or fetus.

In the UK, routine iron supplementation is not recommended. [70] In the US, the CDC recommends daily elemental iron supplementation for prophylaxis or treatment of iron-deficiency anaemia. Absorption of iron can be facilitated with vitamin C. [71] [72] [73]

Management of post-term pregnancy

Post-term pregnancy is defined by the World Health Organization as a gestation that has extended to or beyond 42 weeks. Perinatal mortality at >42 weeks' gestation is twice that at term. Although differences exist between published practice guidelines, women may be offered induction of labour by 41 weeks' gestation to avoid risks of post-term pregnancy. [74] [75] [NICE: induction of labour] If pregnancy continues beyond 41 weeks, twice weekly antenatal testing should be initiated, including a non-stress test and assessment of amniotic fluid volume. [74] [75]

Obesity

Obese women should also be informed that they are at risk for multiple pregnancy complications including gestational hypertension, gestational diabetes mellitus, cardiac disease, pulmonary disease, obstructive sleep apnoea, and caesarean delivery. [49] Regular aerobic exercise during pregnancy may reduce some of these risks. While evidence indicates that monitored physical activity appears to limit gestational weight gain among overweight or obese pregnant women, effects on maternal and neonatal health are unproven. [76] Antenatal dietary modifications in obese pregnant women can reduce maternal weight gain during pregnancy without adversely influencing neonatal birth weight. [77]

Obese patients may also be at increased risk for venous thromboembolism, particularly if other risk factors are present. Thromboprophylaxis should be considered on an individual basis based upon a patient’s risk profile. Antenatal consultation with an anaesthetist should be considered for morbidly obese patients to discuss interventions (such as an early epidural) that may limit intrapartum risk.

Guidelines

In the UK, the National Institute for Health and Clinical Excellence (NICE) has produced the following guidelines and guidance:

• Antenatal care: routine care for the healthy pregnant woman [8]

• Diabetes in pregnancy: management of diabetes and its complications from pre-conception to the postnatal period [61]

• Antenatal and postnatal mental health: clinical management and service guidance [78]

• Pregnancy - routine anti-D prophylaxis for rhesus-negative women. [67]

Guidelines are also available from a number of professional societies on screening for chromosomal abnormalities and neural tube defects:

• Royal College of Obstetrics and Gynaecologists (UK). Amniocentesis and chorionic villus sampling [79]

• Society of Obstetricians and Gynaecologists of Canada. Prenatal screening for fetal aneuploidy [80]

• Society of Obstetricians and Gynaecologists of Canada. Evaluation of prenatally diagnosed structural congenital anomalies [81]

• Society of Obstetricians and Gynaecologists of Canada Genetics Committee. Obstetrical complications associated with abnormal maternal serum markers analytes. [56]

Specific guidelines include:

• Royal College of Obstetrics and Gynaecologists (UK). Reducing the risk of thrombosis and embolism during pregnancy and the puerperium [31]

• Royal College of Obstetrics and Gynaecologists (UK). Air travel and pregnancy. Scientific Advisory Committee opinion paper [32]

• Society of Obstetricians and Gynaecologists of Canada. Immunisation in pregnancy [82]

• Society of Obstetricians and Gynaecologists of Canada. Pre-conceptional vitamin/folic acid supplementation 2007: the use of folic acid in combination with a multivitamin supplement for the prevention of neural tube defects and other congenital anomalies [83]

• Royal College of Obstetrics and Gynaecologists (UK). Female genital mutilation management. [12]