In the Swiss Study ''HIV and pregnancy'' we observed 153 singleton pre
gnancies of HIV-positive women. 23 (15%) of those ended with a prematu
re delivery. For drug addicts (n=100), the incidence of prematurity, 2
0%, significantly higher than in those free of drugs (n=53) with 5.6%.
The most frequent cause of prematurity was premature labor or rupture
of the membranes (n=13), followed by maternal illness (n=8) and fetal
complications (n=2). Women with premature delivery tended to have low
er CD4 cell counts than those with term delivery (29.4% vs 12.0% with
<200 CD4 cells/mu l). Low CD4 cell counts and drug consumption are two
independent but cumulative risks for severe infections. 16 of the 153
women (12 with, 4 without drug consumption) had severe infections dur
ing pregnancy; in 4 cases (25%), this led to prematurity. The most com
mon infection was pneumonia (14/16). further one case of pyelonephriti
s and one of cerebral toxoplasmosis. Two of these 16 infants (12.5%) w
ere HIV-positive. We could not confirm a relationship between prematur
ity and vertical HIV transmission. Of the HIV-classified children, 3/1
8 (16.7%) premature infants and 16/74 (21.6%) term infants were infect
ed.