Data on birth outcome after exposure to azathioprine or mercaptopurine during pregnancy is sparse.
Dr Langagergaard and colleagues from Denmark examined the risk of adverse birth outcome among newborns of women exposed to azathioprine or mercaptopurine during pregnancy.
Data on drug use and births were obtained from Danish population registries.
The researchers included 76 exposed pregnancies in 69 women.
Of these, the team used 64 pregnancies exposed 30 days before conception or during the first trimester to examine the risk of congenital abnormalities.
|The relative risk for low birth weight at term was 4|
|Alimentary Pharmacology & Therapeutics|
The research team evaluated 65 pregnancies exposed during the entire pregnancy to examine preterm birth and low birth weight at term.
The team compared birth outcomes with outcomes among women who did not fill prescriptions for azathioprine or mercaptopurine during pregnancy.
The researchers found that azathioprine- or mercaptopurine-exposed women had a higher risk of adverse birth outcomes than unexposed controls.
The team also limited the comparison to newborns of women with the same types of underlying disease.
The researchers noted that the relative risks for spontaneous and induced preterm birth at term were 1 and 4, respectively.
The team observed that the relative risks for low birth weight, and congenital abnormalities was 1.7 and 1.1, respectively.
Dr Langagergaard's concludes, “Our results suggest that adverse birth outcomes were caused by the underlying disease rather than by use of azathioprine or mercaptopurine.”