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[Within the limits of viability: the dilemma of the obstetrician. A 5-year experience at a perinatal care center].

The study was performed in order to establish the obstetric factors that influence survival of newborns whose birth weight is under 1000 g. All medical records of babies with such birth weight, born alive at the Instituto Nacional de Perinatología in Mexico City during the period from 1991 to 1996 were revised. Babies with congenital malformations, cromomosomopathies or those who after birth were referred to another medical center were excluded. Survival status was used to form two study groups: those who were discharged alive and those who died during their hospital stay. Different obstetric conditions on management were compared between these two groups. Statistical Analysis was performed through t-test, chi square or exact Fisher's test. Two hundred and ninety two cases were included out of 294. Sixty nine (25.4%) survived while 203 (74.6%) died during their hospitalization. Several obstetric conditions were found to have statistical differences between survivors (S) and non survivors (NS): cervical dilatation on admittance to hospital (1.6 cm among S and 2.7 among NS), cervical dilatation prior to resolution (3.3 cm S vs 4.9 cm NS), gestational age (28.3 vs 27 weeks). Newborn conditions also showed significant statistical differences as in birth weight (867.1 vs 795.5 g), 1 minute Apgar (4.1 vs 2.5), and 5 min Apgar (6.9 vs 5). Use of antepartum steroids showed a striking difference between groups while duration of labor, usage of oxitocin and way of delivery showed no statistical differences. Gestational age (over 28 weeks), birth weight (above 867 g) and the use of antepartum steroids are of extreme importance in the survival status of babies born weighting less than 1000 g.