MATERNAL AND EARLY CHILD HEALTH

Health Evidence Bulletins - Wales

Date of Completion: 27.10.97

The contents of this bulletin are likely to be valid for approximately one year, by which time significantly new research evidence may become available


22. Congenital abnormalities

(Users are advised to consult the supporting evidence for a consideration of all the implications of a recommendation)

In considering the prevalence of any congenital anomaly it is important to include not only live and stillborn infants but also spontaneous miscarriage and pregnancies terminated subsequent to antenatal diagnosis of a major abnormality which will, for many families, represent an equally great if different tragedy to the survival of a handicapped child. Antenatal diagnosis of abnormality allows parents not only the option of termination but also time to plan care for the child(i).
Reported prevalence rates (underestimates based on a voluntary notification scheme of live births and terminations) are:
All congenital malformations - 84.9 per 10000 (1993)(ii);
Major structural abnormality - 18 per 10000(1993);
Down’s syndrome - 0.92 per 1000 (1993) (iii);
Neural tube defects - 0.8 per 1000 (1992) (iv);
Heart malformations - 4.7 per 1000 live births (1985-1990) (v).
i. The OPCS monitoring scheme for congenital malformations. Occasional paper 43. London: HMSO, 1995 (Type V evidence - expert opinion)
ii. Office for National Statistics. Congenital malformation statistics: notifications 1993. Series MB3 No. 9 London: HMSO, 1996;
iii. Alberman E, Mutton D, Ide R, Nicholson A, Borrow M. Down’s syndrome births and pregnancy terminations in 1989-1993: preliminary findings. British Journal of Obstetrics and Gynaecology. 1995; 102: 445-447;
iv. Hey K, O’Donnell M, Murphy M, Jones N, Botting B. Use of local neural tube defect registers to interpret national trends. Archives of disease in childhood. 1991; 71: F198-F202;
v. Abu-Harb M, Hey E, Wren C. Death in infancy from unrecognised congenital heart disease. Archives of disease in children. 1994; 71: 3-7 (nos. ii-v : Type IV evidence - statistical information)
The Statements The Evidence
22a. Population screening is conventionally offered for chromosome abnormalities and neural tube defects. The potential benefits and adverse effects of serum testing and/or ultrasound should be available for parents, verbally and with the help of literature, so that informed decisions can be made (i).
(Health gain notation - 3 "trade-off between beneficial and adverse effects")
i. Enkin M, Keirse MJNC, Renfrew M, Neilson J. A guide to effective care in pregnancy and childbirth. 2nd ed. Oxford: Oxford University Press, 1995. pp. 45-51
(Type V evidence - expert opinion) 
22b. All professionals who offer antenatal screening require education and ongoing training in a rapidly changing field(i).

(Health gain notation - 2 "Likely to be beneficial")

i. Enkin M, Keirse MJNC, Renfrew M, Neilson J. A guide to effective care in pregnancy and childbirth. 2nd ed. Oxford: Oxford University Press, 1995. pp. 46-47
(Type V evidence - expert opinion) 
22c. Ultrasound is likely to identify the majority of major abnormalities(i, ii). Recent developments in technique and technology mean that trials only a few years old are out of date. All new techniques such as the use of markers (nuchal thickness) for first trimester diagnosis of chromosomal abnormality should be the subject of controlled trial before adoption into practice(ii).

(Health gain notation - 2 "likely to be beneficial")

 i. Chalmers I, Enkin M, Keirse MJNC. Effective care in pregnancy and childbirth. Oxford: Oxford University Press, 1989 p. 372
(Type IV evidence - observational studies. Summary in Enkin M, Keirse MJNC, Renfrew M, Neilson J. A guide to effective care in pregnancy and childbirth. 2nd ed. Oxford: Oxford University Press. 1995. p. 47-48);
ii. Royal College of Obstetricians and Gynaecologists. Report of the working party on ultrasound screening for fetal abnormalities. Consultation document. London: RCOG, March 1997
(Type V evidence - expert opinion)

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22d. Adoption of population screening by an 18-20 week scan for structural abnormality has been widely debated (i).

(Health gain notation - 4 "unknown")

 i. Royal College of Obstetricians and Gynaecologists. Report of the working party on ultrasound screening for fetal abnormalities. Consultation document. London: RCOG, March 1997
(Type I evidence - systematic review)
 22e. It is beneficial to provide pre- and peri-conceptual folic acid supplementation to prevent recurrent neural tube defects(i, ii).
(Health gain notation - 1 "beneficial")
i. MRC Vitamin Study Research Group. Prevention of neural tube defects: Results of the Medical Research Council vitamin study. Lancet. 1991; 338: 131-137
(Type II evidence - randomised controlled trial, 1817 women)
22f. The evidence indicates that rubella vaccination in the early postpartum period for seronegative women is safe and effective. The opportunity for immunization should not be missed (i).
(Health gain notation - 2 "Likely to be beneficial")
i. Chalmers I, Enkin M, Keirse MJNC. Effective care in pregnancy and childbirth. Oxford: Oxford University Press, 1989 p. 541-542
(Type I evidence - systematic reviews. Summary in Enkin M, Keirse MJNC, Renfrew M, Neilson J. A guide to effective care in pregnancy and childbirth. 2nd ed. Oxford: Oxford University Press. 1995. p. 117-119)
22g. Recommendations for the optimum performance of amniocentesis are available (i, ii).

(Health gain notation - 2 "Likely to be beneficial")

i. Royal College of Obstetricians and Gynaecologists. Amniocentesis. Guideline No.8. London: Royal College of Obstetricians and Gynaecologists, 1996
(Type V evidence - expert opinon);
ii. Benbow A, Semple D, Maresh M. Royal College of Obstetricians and Gynaecologists Clinical Audit Unit. Effective procedures in maternity care suitable for audit. London: Royal College of Obstetricians and Gynaecologists, June 1997. pp. 11-14
(Review of effective procedures, classified according to evidence type)
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Health Evidence Bulletins: Wales, Duthie Library, UWCM, Cardiff CF14 4XN. e-mail: weightmanal@cardiff.ac.uk