Majority of B.C. women take prescription drugs during pregnancy, Canadian study shows

The study, published online December 15 in the journal Clinical Therapeutics, is the first of its kind in Canada. Researchers analyzed population-based outpatient prescription claims data for patterns of prescription drug use during pregnancy in B.C. from 2001 to 2006.

The researchers found that 63.5 per cent of pregnant women in B.C. filled at least one prescription. One in thirteen -- or 7.8 per cent -- filled a prescription for a medicine known to be risky in pregnancy -- most often for select medicines for anxiety, insomnia and depression. Drugs that are strictly contraindicated pregnancy, however, were filled in less than 0.5% of pregnancies.

"Although much remains to be understood about the appropriateness of medicine use that actually occurs among pregnant women in B.C., one encouraging finding from our study is that existing use of medicines with known risks declines dramatically when women become pregnant," says co-author Steve Morgan, an associate professor in the School of Population and Public Health (SPPH) and Associate Director of the Centre for Health Services and Policy Research (CHSPR).

On average, pregnant women filled 2.6 different types of drugs, while 15 per cent used five or more prescription medications during their pregnancy. Prescriptions most frequently filled during pregnancy were for antibiotics (30.5 per cent), respiratory drugs (25.7 per cent), dermatologics (13.4 per cent), and drugs that act on the nervous system (12.8 per cent).

Other study findings include:

• The use of medicines in pregnancy slightly increased over time, going from 63 per cent of women in 2001 to 66 per cent in 2006.
• Women aged 20 years or younger were most likely to take prescription drugs during pregnancy (69 per cent) while the lowest rate occurred among those aged 30 to 35 years (62 per cent).
• Prescription medication use was also high in the first three months immediately following delivery, a period when women may be breastfeeding, with 61.3 per cent of women filling prescriptions.

"Since pregnant women are normally excluded from clinical trials of new drugs and post-market study is limited, there is little evidence on the risks and benefits of many of the most commonly used drugs in pregnancy," says lead author Jamie Daw, a researcher at CHSPR, part of SPPH. "Given the prevalence of prescription drug use, more research is needed to help pregnant women and their physicians make informed decisions."