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Medication use during pregnancy: data from the Avon Longitudinal Study of Parents and Children



To present data on the self-reported use of all types of medicinal products collected during pregnancy in a large cohort in southwest England.


Pregnant women with a delivery date during 1991-1992 and forming part of the prospective, population-based Avon Longitudinal Study of Parents and Children (ALSPAC) were sent up to four self-completion postal questionnaires during pregnancy. Text data collected from the questions on drug usage were coded using an ALSPAC drug dictionary based on the World Health Organization Drug Dictionary.


At least one antenatal self-completion questionnaire was completed for 14,119 pregnancies, and 11,545 women completed all four. The data included prescription, over-the-counter, herbal and homeopathic products as well as iron, vitamins and other supplements. Only 7.6% did not report use of any medicinal product throughout their entire pregnancy. The remaining 92.4% used at least one product at some stage. After exclusion of iron, folate, vitamins, supplements, herbal and homeopathic products and skin emollients, 83% of those completing all questionnaires had used conventional therapeutic drugs. Analgesics were reported by approximately one-third of women at each stage during pregnancy, and paracetamol was the most frequently reported substance. Iron preparations were reported by 33% of the full cohort, at some stage, and folate by 21.9%. Use of anti-anaemic products increased during pregnancy with the greatest incidence at 32 weeks. Other vitamins and supplements were taken by 17.4% at some stage. Use of vitamins decreased throughout pregnancy from 9.6% in early pregnancy to 5% at 32 weeks. Antacids were reported by 23% at 32 weeks. The reported incidence of antibiotic use decreased slightly during pregnancy from 8% early on to 5.8% at 32 weeks; amoxicillin was the most frequently reported antibacterial.


Use of medicinal products was high during pregnancy in the ALSPAC cohort. This finding is consistent with data from recent publications.

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We are extremely grateful to all the mothers who took part and to the midwives for their co-operation and help in recruitment. The whole ALSPAC study team comprises interviewers, computer technicians, laboratory technicians, clerical workers, research scientists, volunteers and managers who continue to make the study possible. This study could not have been undertaken without the financial support of various organisations including the Wellcome Trust, the Medical Research Council, the University of Bristol, the Department of Health and the Department of the Environment. The ALSPAC study is part of the WHO-initiated European Longitudinal Study of Pregnancy and Childhood. The study complies with current British law including ethics approval.

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Headley, J., Northstone, K., Simmons, H. et al. Medication use during pregnancy: data from the Avon Longitudinal Study of Parents and Children. Eur J Clin Pharmacol 60, 355–361 (2004).

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  • Pregnancy
  • Drug use
  • Medication