Gaining too much weight during pregnancy is linked to greater use of health care services and longer hospital stays, according to a study by the federal Centers for Disease Control and Prevention and Kaiser Permanente Northwest Center for Health Research.

The study, the first to document the effect of obesity during pregnancy on the use of health care services, collected data on 13,442 pregnancies that occurred from 2000 to 2004.

The researchers discovered that obese women have significantly longer hospital stays and require more medications, more prenatal fetal tests, obstetrical ultrasonograms, make more telephone calls to the ob-gyn department and prenatal visits with physicians, compared with normal-weight women. And all these happen due to complications such as high blood pressure, preeclampsia, gestational diabetes and Caesarean deliveries, researchers found.

For most obese women, a hospital stay was 4.1 days longer than it was for normal-weight women, the study found. Caesarian delivery rates were 45.2 percent for extremely obese women, compared to 21.3 percent for normal weight women. The number of sonograms for high-risk normal women was 6.6 versus 11.0 for obese women.

“Obesity during pregnancy is associated with more use of health-care services. Even if there is a small increase, it is going to have substantial financial implications,” said lead researcher Susan Y. Chu, a senior epidemiologist at the CDC.

The study also found that the number of women who become obese during pregnancy is on the rise in the U.S., which is also a major reason of concern for the healthcare department and also for the economy.

“Right now, about one in five women in the United States who deliver babies are obese. Given that there are about 4 million births in the United States each year that translates to almost 1 million obese women giving birth. The increased health care use by obese pregnant women will have substantial cost implications,” explained Dr. Chu said.

And as if these weren’t enough reason of concern, a study by the Department of Ambulatory Care and Prevention of Harvard Medical School (HMS) and Harvard Pilgrim Health Care, published in the April 2007 issue of the American of Obstetrics and Gynecology, warned that pregnant women who gain excessive weight are four times likely to have a baby who becomes overweight in early childhood. “Maternal weight gain during pregnancy is an important determinant in birth outcomes,” said lead author Emily Oken, instructor in the Department of Ambulatory Care and Prevention in the study.

Dr. Chu’s findings were published in the April 3 issue of the New England Journal of Medicine.