NEW YORK: Obese women are at increased risk of having their infant die soon after birth, especially if premature rupture of membranes (PROM) occurs before full-term, according to a report in the journal Obstetrics & Gynecology .

These findings may indicate there is a problem in how obese women with preterm PROM births are treated, Dr. Ellen A. Nohr from University of Aarhus, Denmark said. It is also possible that "preterm infants of obese mothers may be more susceptible when they are not protected by the membranes." PROM occurs when the membranes rupture before labour begins, which is usually followed by labour and delivery. Umbilical cord compression is the primary risk for the foetus, while infection within the uterus is the major complication in the woman.

Nohr and colleagues used the Danish National Birth Cohort to investigate the association between pre-pregnancy obesity and infant mortality, with focus upon different types of preterm births. The infant mortality rate was higher in infants of overweight and obese mothers than in infants of normal-weight mothers, the authors report, even after consideration of other maternal and infant risk factors.

Mortality in infants born after preterm PROM was more than tripled in infants of overweight women and was increased nearly six-fold in infants of obese women, the report indicates. High body mass index was not, however, associated with mortality in infants born after spontaneous preterm births without preterm PROM.

The results were similar in infants with or without malformations and after exclusion of infants born to women with obesity-related diseases or infants born to sub-fertile women, the researchers note. "This is the first study indicating an elevated mortality in infants of obese mothers after preterm PROM, and it is therefore too early to suggest changes in the management of pregnancies in obese women," Nohr said.

"However, if these findings are causal and we understand the mechanisms behind them, it may be possible to suggest preventive measures," she added.