Are low-dose oral contraceptives safer and better?

Abstract

It is widely believed that the use of low-dose oral contraceptives decreases thrombotic risks, compared with higher-dose oral contraceptives. Two recent epidemiologic studies infer a lower risk with 30 to 35 mcg than with 50 mcg estrogen oral contraceptives. However, as with prior studies from which similar conclusions were drawn, these studies have major flaws, the worst being that all 50 mcg oral contraceptives are lumped together, whereas 50 mcg mestranol oral contraceptives are actually bioequivalent to 35 mcg ethinyl estradiol oral contraceptives, thus confounding all such studies. Moreover, while rare thrombotic events have received inordinate attention, the major protective effect against endometrial and ovarian cancer that has been shown in older studies among users of oral contraceptives containing > or = 50 mcg ethinyl estradiol or > or = 80 mcg mestranol are almost totally ignored. The theoretical benefits of using lower-dose oral contraceptives have not been demonstrated, whereas the protection against these types of reproductive cancer have been shown repeatedly with high-dose oral contraceptives but not, to date, with lower-dose oral contraceptives. Such protection may be diminished by lowering the oral contraceptive dosage. Should every woman of reproductive age use high-dose oral contraceptives for 2 years? Are we throwing out the baby with the bath water?