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At the heart of general practice since 1960

Antenatal screening: key facts and figures

Facts

lLots of women undergo screening in pregnancy and have examinations and tests, but sometimes the evidence for these is scant.

lWomen and their partners must be given unbiased information on screening and the outcomes, what to expect from results and options for management.

lAll women should be offered screening for Down's syndrome and neural tube defects according to local policy.

lScreening for haemoglobinopathy should be offered to all people at risk. If more than 15 per cent of the local population fulfil these criteria, universal screening should be undertaken.

lRoutine early ultrasound increases the detection of multiple pregnancies and decreases the rate of induction of labour for post-date pregnancy.

lTesting for rubella immunity should be offered to all women. Those who are seronegative should be offered vaccination post delivery.

lRhesus status and antibody screening should be determined early in pregnancy and at 28 and 36 weeks. The appropriate use of anti-D IgG is vital.

lScreening for syphilis, bacteruria, hepatitis B and HIV should be offered.

lFolic acid is recommended in women trying to conceive and until 12 weeks.

lWomen should be encouraged to stop smoking in pregnancy.

lHeavy alcohol use in pregnancy should be avoided but there is no justification for encouraging women not to drink at all.

lRoutine fundal height measurement is a flawed method of assessing fetal size.

lIf a pregnant woman is not immune to chickenpox and is exposed in pregnancy, she should be given varicella zoster immunoglobulin as soon as possible up to 10 days after contact.

Key papers

lRoyal College of Obstetricians and Gynaecologists. Report of the working party on biochemical markers and the detection of Down's syndrome. London: Royal College of Obstetricians and Gynaecologists, 1993

lCrickle H. Biochemical and ultrasound screening for Down's syndrome: rival or partners? Ultrasound in obstetrics and gynaecology 1996;7:236-8

lDepartment of Health. Report on Working Party of the Standing Committee on Sickle Cell, Thalassaemia and the Haemoglobinopathies. London: HMSO, 1993

Prophylactic management, crisis intervention and expert management can alleviate complications.

lPregnancy and Childbirth Module of the Cochrane Database of Systematic Reviews. In: Cochrane Library; the Cochrane Collaboration, Issue 2, Oxford, Update Software

Early ultrasound can detect gross abnormalities but has not been shown to affect perinatal mortality except by selected termination.

lSmaill F. The postpartum rubella vaccination. In: Enkin MW et al (eds). The pregnancy and childbirth module of the Cochrane Database of Systematic Reviews, Oxford: Update Software 1995

Maternal infection early in pregnancy can result in fetal death, low birthweight, deafness, cataracts, jaundice, purpura, hepatosplenomegally, congenital heart disease and mental impairment.

lLee D et al. Guidelines in the use of anti-D immunoglobulin for Rh prophylaxis. Joint working group of the British Blood Transfusion Society and the Royal College of Obstetricians and Gynaecologists, 1997

Far fewer Rh disease women are becoming sensitised. The commonest causes are likely to be silent sensitisation and failure to give anti-D IgG appropriately. Bleeds from the fetus in the last 12 weeks of pregnancy may go undetected.

lNicoll A, Moisley C. Antenatal screening for syphilis. BMJ 1994;308:254-5

Consequences of infection are significant, causing miscarriage, prenatal and congenital problems. Screening should be offered early.

lSmaill F. Antibiotic vs no treatment for asymptomatic bacteriuria In: Enkin MW et al (eds). Pregnancy and Childbirth Module of the Cochrane Database of Systematic Reviews.

lRomero R et al. Meta-analysis of the relationship between asymptomatic bacteriuria and preterm delivery and low birthweight. Obstetrics and Gynaecology 1989;73:576-82

UTI is considered the most common medical complication of pregnancy.

lWilliams JR et al. The transmission dynamics of hepatitis B in the UK: a mathematical model for evaluating costs and effectiveness of immunisation programmes. Epidem Infect 1996;116:71-89

Routine testing of pregnant women is now recommended.

lMRC Vitamins Study Group. Prevention of neural tube defects: results of the Medical Research Vitamin Study. Lancet 1991;238:131-7

Women with diabetes and those on anticonvulsants are at higher risk, and those with history of neural tube defects or family history of such should take

5mg folic acid, otherwise 4mg is adequate.

lLumley S. Strategies for Reducing Smoking in Pregnancy. In: Enkin MW et al (eds). Pregnancy and Childbirth. The Cochrane Database of Systematic Reviews, 1995

lBlair PS et al. Smoking and Sudden Infant Death Syndrome in results from 1993/5. Case control study for confidential inquiries into stillbirths and deaths in infancy. BMJ 1996;313:195-8

The evidence that smoking is harmful in pregnancy is strong. The effects on perinatal outcomes is more controversial.

lThe Royal College of Obstetricians and Gynaecologists. Alcohol in Pregnancy. Guildeline No. 9. London: 1996

Heavy alcohol use in pregnancy causes fetal alcohol syndrome.

lEnders G et al. Consequences of varicella and herpes zoster in pregnancy. Prospective study of 1,739 cases: Lancet 1994;343:1548-51

Any close contact during the period of infectiousness is significant in pregnancy.

lMacdonagh SE et al. Antenatal HIV testing in London, policy, uptake and detection. BMJ 1996; 313: 532-3

Transmission to the fetus can be substantially reduced by not breast-feeding, use of AZT and elective Caesarean section.

Dr John Mellor discusses this key exam topic

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