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Audit of process of antenatal screening for sickle cell disorders at a north London hospital

BMJ 1997; 315 doi: https://doi.org/10.1136/bmj.315.7111.784 (Published 27 September 1997) Cite this as: BMJ 1997;315:784
  1. Helen Neuenschwander, London academic training scheme registrara,
  2. Bernadette Modell (b.modell{at}ucl.ac.uk), professor of community geneticsa
  1. a Department of Primary Care and Population Sciences, University College London Medical School, Whittington Hospital, London N19 5HT
  1. Correspondence to: Professor Modell
  • Accepted 28 May 1997

Introduction

Antenatal screening for haemoglobin disorders (sickle cell disorders and thalassaemias) is now routine.1 Couples who are at risk have a strong preference for prenatal diagnosis during the first trimester,2 but most are identified too late for this in the presenting pregnancy.3 We studied the process of antenatal screening and counselling for sickle cell disorders at this hospital, where 40% of births are in groups at risk. The hospital has a policy of universal antenatal and neonatal screening for haemoglobin disorders. Two community based haemoglobinopathy counsellors are notified when a pregnant carrier is identified and invite the couple within two days to attend for testing of the partner and counselling. About 80% of couples attend. Couples who are interested in prenatal diagnosis are referred to a specialist centre.

Subjects, methods, and results

Thirty one women at risk were identified among those booking for antenatal care between 1 January and 31 December 1994: 29 from laboratory records and two after the birth of an affected child. Since couples at risk have a 1 in 4 chance of having an affected child, this suggests that about six additional couples were not identified. The number of couples at risk was probably about 37. Obstetric notes were reviewed. Six women were of African Caribbean descent and 25 of African descent. Eleven were primiparous (most of whom were unaware of their risk before this pregnancy) and 20 were multiparous (most of whom had been screened and informed of their risk in a previous pregnancy). Gestation at the time of the first visit to the general practitioner, booking for antenatal care, and counselling are shown in the 1.

Figure1

Gestation (weeks) at three points in antenatal screening for haemoglobin disorders—first visit to the general practitioner, booking for antenatal care, and counselling—in 31 women at risk of having children with sickle cell disorder. Black bars denote those who had prenatal testing

In the 11 primiparous women the mean gestation at the first visit to the general practitioner was 11.9 weeks, at booking 15.7 weeks, at partner's blood test result 19.2 weeks, and at counselling 19.5 weeks. Three couples did not attend counselling. All declined prenatal testing; one attended the specialist centre for counselling at 16 weeks' gestation. Seven out of 11 liveborn children had a sickle cell disorder.

In the 20 multiparous women the mean gestation at the first visit to the general practitioner was 9.2 weeks. Two of the 20 women were referred directly to the prenatal diagnosis centre for counselling and had early prenatal testing. One affected fetus was aborted. Mean gestation at booking in the remaining 19 cases was 12.6 weeks and at counselling 15.3 weeks. Three out of four further couples referred to the specialist centre had prenatal diagnosis (at 11, 11.3, and 17.3 weeks). No fetus was diagnosed as affected, but one pregnancy miscarried. One woman declined prenatal testing because of a poor obstetric history, and she later miscarried. Two out of 17 liveborn children had a sickle cell disorder. Overall, 1 in 10 affected pregnancies was detected prenatally and terminated.

Comment

The use of prenatal diagnosis for sickle cell disorders observed here (5/37, 13.5%) is typical for London, so the data are representative though the numbers are small.3 Antenatal screening as presently practised does not meet patients' needs for early information and counselling. Instead it leads to late recognition of risk in both the index and subsequent pregnancies and a correspondingly low uptake of prenatal testing.2 Only the two couples whose general practitioner referred them directly to the specialist centre had assured access to first trimester diagnosis.

Primary care teams could improve services by referring women (or couples) known to be at risk for counselling as soon as pregnancy is reported, simultaneously screening both partners when a woman in a risk group reports a pregnancy, and opportunistically offering screening before a woman becomes pregnant.4 We plan to issue couples at risk with a card that emphasises the importance of early counselling in pregnancy and to build a routine audit of the screening process into counselling records.

Acknowledgments

We thank the obstetricians of the Whittington Hospital and Ms Lorna Bennett, haemoglobinopathy counsellor at the Bloomsbury and Islington Sickle Cell and Thalassaemia Centre, for their cooperation; and Sharon See-Tai for statistical advice.

Funding: BM is a Wellcome principal research fellow.

Conflict of interest: None.

References

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