Researchers determine how many women take prescription medications during pregnancy

A new study investigating the safety of medication during pregnancy has found that about 60% of women are prescribed a medication during pregnancy.

The study, published in Pharmacoepidemiology and Drug Safety, was led by Professor Gareth Baynam, from UWA Medical School and head of the Western Australian Register of Development Anomalies (WARDA).

"Pregnant women have traditionally been excluded from research examining the safety of medications, which has resulted in a lack of adequate data," Professor Baynam said.

In the study, 30% of women used a medication that was classified by the Therapeutic Goods Administration as having insufficient data on its safety, and about 15% of women were using medication with known risks.

"Medications are commonly used during pregnancy to manage pre-existing conditions and conditions that arise during pregnancy," Professor Baynam said.

"With around 50% of pregnancies being unplanned, unintentional medication exposure is common. Medications used during pregnancy can cross the placenta and adversely affect fetal development and neonatal outcomes."

The study examined medications dispensed under the national Pharmaceutical Benefits Scheme to pregnant women in Western Australia overall and by medication safety category.

"This study sets the foundation for the most comprehensive assessment of the effect of prescription medicines on babies ever done in WA," Professor Baynam said.

"The implications are profound for the prevention and diagnosis of birth defects that affect one in 20 babies and are a large class of rare, but cumulatively frequent, diseases."

The effects of medication on pregnancy outcomes can vary depending on the dose, amount, timing and length of exposure.

"Medication exposure during the first trimester is most likely to be associated with an increased risk of congenital anomalies," Professor Baynam said.