Summer Viruses May Play Role in Low Birth Weight


MONTEREY, CALIF. — July and August are the peak months for delivering babies weighing less than 1,500 g, but the summer months are not associated with preterm birth, according to a retrospective review from the University of Southern California's Women and Children's Hospital.

The study of 4,108 singleton live births in the 3 years from 2002 through 2004 found no seasonality to preterm deliveries, defined as births before 38 weeks' gestational age. The increase in low-birth-weight babies in summer may correlate with seasonal “summer virus” infections including enteroviruses, adenoviruses, and others, Dr. Ozlem Equils and her associates reported in a poster presentation at the annual meeting of the Infectious Diseases Society for Obstetrics and Gynecology.

In 2002, approximately 13% of babies born in August were low birth weight. About 7% were low birth weight in July 2003, and 6% in July 2004, said Dr. Equils of Cedars-Sinai Medical Center, Los Angeles. Those proportions were higher than in other months of the same years.

Bacterial and viral infections have been associated with preterm birth in other epidemiologic studies, and animal studies have shown an association between infection with enterovirus and preterm birth.

“We know that enterovirus has caused nursing outbreaks—the mother and the baby get sick. We think that it may play a role with these small babies,” Dr. Equils suggested in an interview at the poster.

Obstetricians may want to follow the viral outbreaks in their communities and emphasize infection prevention with patients, she added. If enterovirus is going around, for example, diligent hand washing and perhaps limiting intercourse in the later part of pregnancy may be advisable.

The investigators hope to study placenta samples to see if viruses are present and associated with seasonality and low birth weight. If further research supports these very preliminary associations, it may be possible to identify the presence of viruses from maternal cervical secretions and offer treatment, potentially reducing low-birth-weight deliveries, she speculated.

Previous studies of seasonality and preterm delivery come mainly from developing countries where factors such as droughts and starvation confound the data. It's also difficult to extrapolate observations on seasonality and preterm birth from developed countries in the 1960s through 1980s because of changing environmental conditions and other factors, such as more women entering the labor force, she said.

Next Article: