[Maternal factors associated to prematurity]

Prematurity is the main cause of morbidity-mortality in developed countries newborns, and it is responsible of most none malformed newborn deaths, and half congenital neurological disability.

To determine the association between socio-economic, demographic, and obstetric maternal history, evolution of pregnancy, and premature delivery.

A cohort of live newborns was studied at Centro Médico Nacional Ignacio García Téllez since January 1st 2000 to December 31st 2004, with birth weight of 500 g or higher. Premature newborns were considered cases and those with 37 weeks of gestational age or more were controls. Prematurity prevalence was compared with and without risk factors. For each studied history it was calculated odds ratio (OR) with 95% confidence interval (95% CI), and attributed fraction in exposed and in population.

Prematurity rate observed was 11.9% (3,018/25,355). Most remarkable risk factors associated with prematurity are: illiterate mother (OR 1.54; 95% CI; 1.2-1.94), single mother, 36 years old or more (OR 1.81; 95% CI; 1.56-2.09), history of preterm delivery (OR 2.21; 95% CI; 1.54-3.16), multifetal pregnancy, obstetric morbidity (preeclampsia/eclampsia; OR 7.9; 95% CI; 6.6-9.4), gestational diabetes (OR 2.3; 95% CI; 1.75-2.92), urinary tract (OR 1.8; 95% CI; 1.56-1.96) and vaginal infection, premature rupture of membranes, oligohydramnios, polihydramnios (OR 4.48; 95% CI; 3.04-6.6), placenta previa, and abruptio placentae (OR 9.96; 95% CI; 5.62-17.7). There was not a gestational risk factor in 43% (1302/3018) of preterm deliveries.

Premature rupture of membranes and maternal morbidity during pregnancy were the most important risk factors of prematurity.