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TUESDAY, Aug. 5, 2003 (HealthDayNews) -- Pregnant women who were in or near the World Trade Center on Sept. 11, 2001 and shortly after apparently had double the risk of delivering smaller babies compared to women who were in New York City but not near the site of the terrorist attack.
Although the babies born to these women seem to be doing OK, researchers say this reinforces the notion that exposure to smoke and chemicals can stunt the growth of a fetus.
"The frequency of small-for-date babies was twice as high among moms who were down among and near the World Trade Center and those who delivered uptown," says Dr. Philip J. Landrigan, chairman of the Department of Community and Preventive Medicine at Mount Sinai School of Medicine in New York City and one of the collaborators on a research letter appearing in the Aug. 6 issue of the Journal of the American Medical Association.
The authors speculate exposure to various chemicals near the site were responsible for the phenomenon.
The babies suffered from what is known as intrauterine growth restriction (IUGR), which means the baby is below the 10th percentile in weight for a particular gestational age, says Dr. Maureen Malee, director of maternal fetal medicine at the University of Miami School of Medicine. These infants did not grow at a normal rate inside the uterus.
Exposure to air pollution has been associated with both IUGR and pre-term deliveries. "Women who live in areas with heavy air pollution have been shown to give birth to small-for-date babies. Other causes of IUGR that have been reported are, first and foremost, cigarette smoking," Landrigan says. "We think the most plausible explanation [for the current findings] is Mom's exposure to dust and soot in the aftermath of the attacks on the towers and, given that the composition of the towers is fundamentally not dissimilar from air pollution or cigarette smoke, it makes biological sense."
According to the authors, the collapse of the twin towers released a toxic plume containing soot, benzene, polycyclic aromatic hydrocarbons (PAHs), heavy metals, pulverized glass and cement and alkaline particulates.
The study authors looked at 182 women who were pregnant and located in one of five "exposure zones" near Ground Zero at the time of the attack or in the three ensuing weeks. All of the women gave birth at Mount Sinai Medical Center on Manhattan's Upper East Side.
Most of the women had volunteered for the study as a result of media publicity or after seeing an advertisement, a flier, or because their obstetrician had received a letter from the study authors and had referred them.
These women were compared to a control group of 2,367 women who had also delivered babies at Mount Sinai Medical Center but who were not known to have been in lower Manhattan during the critical time frame.
The length of the pregnancies was roughly equivalent in each group (39.1 weeks in the World Trade Center group and 39 weeks in the other).
"We used four different yardsticks to determine whether exposures from the WTC had negative effects on the health of babies born to women who were in and near Ground Zero on Sept. 11," Landrigan explains.
On the three less sensitive measures, there were no statistically significant differences. Specifically, mean birth weight in the WTC babies was 7.06 pounds and 7.2 pounds in the other group. The percentage of low birth-weight babies was 8.2 percent in the WTC group and 6.8 percent in the uptown group. Finally, the frequency of pre-term births was 9.9 percent in the WTC babies and 9.2 percent in the uptown babies.
"None of these yardsticks was able to detect any statistically significant abnormalities between our two groups, although in each case there was a slightly higher problem rate in the WTC babies than in the uptown babies," Landrigan notes.
However, when the researchers measured birth weight in relation to gestational age, a more precise and sensitive yardstick, a different picture emerged. "It relates a baby's weight at birth to the exact duration of time that the baby spent in the womb," Landrigan says. "That, we believe, is why we were able to detect a difference between the groups with this very precise yardstick and not with the others." In the WTC group, 8.2 percent of the babies had IUGR, while only 3.8 percent of the uptown babies were in that category.
The women who had delivered restricted-growth babies had been exposed to the WTC plume at different times during their pregnancy. "The women were evenly distributed all across nine months," Landrigan confirms. "They had terribly intense but very brief exposures. Others lived and worked nearby and had more prolonged exposure, [but] I would characterize most of the exposures as having been brief and intense. The important thing was not the duration of the exposure but the total amount of material that comes into a woman's body."
"They did have a statistically significant result. There was a twofold increase in growth restriction. That's pretty striking," says Malee, who nevertheless cautions the study is a small one and the phenomenon appears to be isolated.
Growth-restricted babies do have a higher incidence of hypertension as adults, Malee says. And Mount Sinai has received grants to bring the babies back at regular intervals for "careful standardized developmental examinations."
But the jury is out when it comes to what the future holds for these tiny babies. "We don't know with any degree of certainty what might happen to the babies. Only time will tell," Landrigan says. "It's just one more tail on that terrible event."