Spike in New York Preemie Deliveries in Days Following Sept. 11

BERKELEY, Calif., Oct. 11 -- Within days of the Sept. 11, 2001 attacks on the World Trade Center, the number of low-birth-weight babies born in New York City rose significantly, found researchers here.

An analysis of birth certificate data for city residents revealed a 44% increase in the risk of delivering a baby weighing less than 1,500 g in the week following the attacks (P =0.007) and a 67% increase in the risk of babies less than 2,000 g (P =0.01), said Brenda Eskenazi, Ph.D., of the University of California School of Public Health at Berkeley, and colleagues.

After the initial increase, there was second sharp rise in very low- birth-weight babies in April 2002, which reflected women who were in the first or second trimester at the time of the attacks, reported Dr. Eskenazi online in Human Reproduction.

"There has been a lot of anecdotal evidence that stress could result in early delivery," Dr. Eskenazi added in an interview. "This does contribute to that evidence, another building block of information."

She and her colleagues reviewed data from more than 1.6 million births in New York State from January 1996 though December 2002. Births in New York City were sorted by borough, and Manhattan residents were further categorized by zip code into lower Manhattan (near the World Trade Center), midtown Manhattan, and upper Manhattan. The authors also assessed residents of Nassau and Suffolk counties on Long Island to the east and Westchester County, bordering the city to the north.

They searched for low-birth-weight babies born three weeks before the Sept. 11 attacks, a week after the attacks, and during 10 four-week intervals in the year following 9/11. These rates were compared with those in the two years prior to the attacks.

After the initial spike in low-birth-weight infants in New York City, there was no increased risk in the succeeding four-week interval. But rates went up again in two intervals. Rates rose from Dec. 4, 2001 through Jan. 28, 2002, for an adjusted odds ration of 1.36 (P =0.01) in December and 1.28 (P =0.04) in January. Rates increased again during the interval that was 33 to 36 weeks after 9/11 when the risk was 1.29 (P =0.03).

In the city's neighboring counties, the risk for delivering a baby weighing less than 1,500 g was 1.46 in January 2002 (P =0.001) and 1.32 (P =0.03) during April 2002, which was 33 to 36 weeks after the attack.

But Heather S. Lipkind, M.D., of Yale and an investigator with the Department of Health World Trade Center Registry, said there are a number of methodological problems with the study by Dr. Eskenazi and colleagues.

In an interview, she questioned the design that relied on zip codes, "which really doesn't give us any idea about women who may have been exposed because they worked downtown, but lived elsewhere."

Moreover, the data do not include women from New Jersey, even though women living in Hoboken or Jersey City were as close to the World Trade Center as women living in many areas of Manhattan, she said.

"I don't think we can draw any kind of clinical implication from this study," Dr. Lipkind said. "And it doesn't tell us anything about possible long-term developmental problems related to exposure."

Dr. Lipkind said the WTC Registry investigators would be publishing their findings on pregnant women exposed to the attack. That study, which will be published in about six months, will include additional psychological assessment data "that are really necessary in evaluating the possibility of post traumatic stress," she said.

Dr. Eskenazi said her study was not intended as the basis for disaster planning and she agreed that there was not a clear clinical implication.

Nonetheless, she said the sharp increase in low birth weight babies immediately following 9/11, "demonstrate there was something emergent during that period."