Statins are the most commonly used class of drug to treat hyperlipidemia. Since they were first brought to market, statins have been considered contraindicated in pregnancy based on animal data showing terato- genic potential at high doses and concern that they might disrupt cholesterol biosynthesis in the develop- ing fetus.1–3 Because of this, use during pregnancy is rare,4 and data about the effects of in utero exposure on fetal development are scarce in humans.1 5 Those data that do exist derive primarily from registries, small cohort studies, and case reports.1 5–12 These studies have been inconsistent in their findings on the teratogenic potential of statins. For example, a review of sponta- neous reports of exposure to statins during the first tri- mester to the US Food and Drug Administration suggested that lipophillic statins may increase the risk of central nervous system and limb anomalies,5 7 whereas a case series analysis from the National Birth Defects Prevention Study failed to observe the same dis- tribution of defects.10 A meta-analysis of the small num- ber of controlled studies (n=6, including a total of 618 women who used statins) failed to find an increase in the risk of birth defects, although the confidence inter- val was wide (pooled estimate of relative risk 1.15, 95% confidence interval 0.75 to 1.76).3
As the prevalence of risk factors for cardiovascular disease, including hypercholesterolemia, diabetes, hypertension, and obesity in women of reproductive age increases13 and as the indications for statin treat- ment expand,14 it is important to understand whether it is safe to use these drugs in patients who may inadver- tently become pregnant; about half of all pregnancies in the United States are unintended.15 This need is also pressing since preclinical studies suggest a possible role for statins in the prevention of pre-eclampsia as a result of their pleiotropic effects on endothelial function and inflammation; human studies (using pravastatin) have begun examining this potential indication.16
We undertook an epidemiologic study to assess the association between statin use in the first trimester and the risk of congenital malformations, using data derived from a large cohort of Medicaid beneficiaries.