In up to a third of babies born with birth defects, prescription drugs may be to blame, says a review published today in The Obstetrician & Gynaecologist.
The prevalence of congenital abnormalities is estimated to be 2–3% of all births, of which around 1% are thought to be attributable to prescription drug use during pregnancy, say the authors.
Prescription drug use during pregnancy is common, but not enough is known about how these may affect the developing fetus, they conclude.
Most mums to be take medication for pregnancy-related complaints and minor infections. But a small proportion do so for chronic conditions, such as asthma, depression, or high blood pressure.
The authors reviewed the evidence on anti-epileptics and antidepressants taken during pregnancy in particular. In an estimated 1 in 250 pregnancies mums to be take anti-epileptic medication.
National Institute for Health and Clinical Excellence guidelines state that it is not possible to comment on the risks of physical abnormalities potentially caused by the drugs in view of the limited data available.
The review looked at preliminary data collated from the UK Epilepsy and Pregnancy Register which found that the risk of congenital malformations with the use of one anti epilepsy drug was 3.7% (n = 2598), and 6.0% (n = 770) for those women taking two or more.
Up to 4% of women take antidepressants during pregnancy, with 2.3% taking selective serotonin reuptake inhibitors (SSRIs).
A large birth defect registry study found no association between maternal SSRI use and cardiac abnormalities. But the review points out that antidepressant use in late pregnancy is associated with neonatal complications such as premature birth, feeding problems, respiratory distress syndrome, endocrine and metabolic disorders and temperature regulation disorders.
The review concludes that our evidence base for using prescription drugs in pregnancy remains limited and that drug companies do not recruit pregnant women to their clinical trials unless the drug in question is for the treatment of disease associated with pregnancy.
Alastair Sutcliffe, Reader in Child Health, UCL Institute of Child Health and co-author of the review commented: “Pregnant women are excluded from clinical trials, which means when new drugs are released there is almost no information on their safety and efficacy in pregnancy.”
The journal’s Editor–in-Chief, Jason Waugh said: “The maternal physiological changes that occur during pregnancy can alter what the body does to the drug in some cases. More research is needed into the fetal effects of some drugs as there are big gaps in our knowledge.”
Chan M,Wong ICK, Sutcliffe AG. Prescription drug use in pregnancy: more evidence of safety is needed. The Obstetrician & Gynaecologist 2012; 14: 87–92.