Alvaro Nagib Atallah*
H ypertension in pregnancy and statistical pow er
H
ypertension in pregnancy is a m ajor cause of
m aternal and fetal m orbidity. I P reeclam psia,
eclam psia, intrauterine grow th retardation, and
perinatal m ortality are adverse effects associated w ith
hypertension.
A pproxim ately 1 0 percent of pregnant w om en are at risk for com plications attributable to high arterial blood
pressure.2 A lthough the treatm ent of hypertension reduces
the m aternal risks,3 the benefits for the fetus are not yet
c1ear.4
T he treatm ent of hypertension crises, one of the m ost
dangerous types of hypertension in pregnancy m ay be
obtained w ith efficacy using low dose nifedipine (5 m g per
oral), or hydrazaline (5 m g IM ). R educing the dosage is
aim ed at decreasing the risks of m aternal hypotension and
fetal death.5 .6
B oth drugs have about 90 percent efficacy in reducing
blood pressure, but it is not know n w ich drug carriers less risk of adverse effects for the fetus. S uppose that one percent
of fetal deaths could be attributed to one drug, and the other drug could be attributed w ith 0.5 percent; that m eans a 50
percent less chance of fetal deaths. In o rd er to h av e 9 0 p ercen t p o w er to d etect th e refered d ifferen ce o n th e
fetal attrib u tab le m o rtality rate to each o f th ese d ru g s, a stu d y o f 1 4 ,0 0 0 w o m en w ith h y p erten siv e crises w o u ld
b e req u ired .7
A lthough doing a random ized clinical trial of such
m agnitude w ould be very difficult, it w ould certainly not
be im possible - if the question w ere considered relevant
for researchers, and m ore im portantly, for funders. S im ilar situations, as are the cases of drugs adverse effects are
* MD, PhD, MSc
Department of Internal Medicine, Escola Paulista de Medicina Chairman, Editor, Sao Paulo Medical Journal.
com m on in m edical literature, and im portant because they
represent hum an suffering and death.
A proposal for a random ized clinical trial has been
prepared by the E clam psia T rial G roup, aim ed at com paring m agnesium sulfate w ith placebo. T he sam ple size is estim ated
at 14,000 cases. T he trial w ould be collaborati ve, w ith various
groups in E urope and developing countries participating. T he
effort is w orthw hile, as the prevention of eclam psia could
prevent about 50,000 m aternal deaths annually, 99 percent
of w hich occur in the developing w orld.x
REFERENCES
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