Hypertension in pregnancy and statistical power.

Hypertension in pregnancy is a major cause of maternal and fetal morbi dity.! Preeclampsia, eclampsia, intrauterine growth retardation, and perinatal mortality are adverse effects associated with hypertension. Approxi mately 10 percent of pregnant women are at risk for complications attributable to high arterial blood pressure," Although the treatment of hypertension reduces the maternal risks.' the benefits for the fetus are not yet clear.' The treatment of hypertension crises, one of the most dangerous types of hypertension in pregnancy may be obtained with efficacy using low dose nifedipine (5 mg per oral), or hydrazaline (5 mg 1M). Reducing the dos age is aimed at decreasing the risks of maternal hypotension and fetal death.>" Both drugs have about 90 percent efficacy in reducing blood pressure, but it is not known wich drug carriers less risk of adverse effects for the fetus. Suppose that one percent offetal deaths could be attributed to one drug, and the other drug could be attributed with 0.5 percent; that means a 50 percent less chance of fetal deaths. In order to have 90 percent power to detect the refered difference on the fetal attributable mortality rate to each ofthese drugs, a study of 14,000 women with hypertensive crises would be required,? Although doing a randomized clinical trial of such magnitude would be very difficult, it would certainly not be impossible if the question were considered relevant for researchers, and more importantly, for funders. Similar situations, as are the cases of drugs adverse effects are