IJPDS International Journal of Population Data Science

A new study in Northern Ireland, published in the International Journal of Population Data Science (IJPDS), reveals that determining what medicines women take in early pregnancy isn’t as straightforward as it seems—and getting it right could make a real difference when studying medication safety in pregnancy for mothers and babies.

Researchers tracked over 139,000 pregnancies between 2011 and 2016, comparing the medications women told their midwives they had taken to the prescriptions they had received in early pregnancy. They found that while the majority of women had taken at least one medication or supplement, the two sources didn’t always match up. Vitamins and antacids, for example, were often bought over the counter, so women reported taking them far more than appeared in pharmacy records. For all other medications, more prescriptions were issued than women reported. For medicines which women only take for a short time, such as laxatives, antibiotics and antivirals, women may simply not have remembered taking them. It is also possible that women may not report taking some prescribed medications because they either stopped or did not take them during pregnancy. Women with chronic illnesses such as epilepsy, diabetes and hypothyroidism need to continue to take their medication during pregnancy, but surprisingly, our findings for these medications showed some of the lowest agreement between what was prescribed to manage the condition and what mothers reported they tool.

These mismatches matter. Relying on just one source of information doesn’t give a full picture of what medication pregnant women are really taking. As lead researcher, Dr. Maria Loane explains, “Our findings show that to understand medicine use during pregnancy, we need to look at both what women tell us and what’s in the prescription records”

The study highlights the importance of combining information reported to midwives and pharmacy data to get a clearer picture of medication use in pregnancy and raises awareness of the hidden differences between different data sources. These findings have important implications when studying medication safety in pregnancy.

 

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Dr Joanne Given, School of Nursing and Paramedic Science, Ulster University, Northern Ireland

Given, J., Dolk, H., Little, A. and Loane, M. (2025) “Medication use from conception to the first antenatal appointment: agreement between maternal self-report to midwife and prescribing records in Northern Ireland in 2011-2016”, International Journal of Population Data Science, 10(1). doi: 10.23889/ijpds.v10i1.2910.