An analysis of the prepregnancy body mass index of more than 79,000 women in eight counties of Western New York who became pregnant between 1999 and 2003 found that the number of women who were overweight when they became pregnant increased by 11 percent and the number who were obese increased by 8 percent over that time period.
There was a corresponding decrease in the percentage of women who were normal weight or underweight in the prepregnancy period over those five years, results showed. The shift applied regardless of age, ethnicity (black or white), education level, type of insurance, previous live births, urbanization status, median family income and smoking status.
The study appears in the current (Dec. 2005) issue of the American Journal of Obstetrics and Gynecology.
The results are thought to apply to the population-at-large because they are consistent with findings in at least three previous papers and because of the large sample size.
"Cumulatively, 40.5 percent of all patients had pre-pregnancy BMIs in the overweight and obese categories in 2003 compared with 37.1 percent in 1999," said John Yeh, M.D., lead author who is professor and chair of the Department of Gynecology-Obstetrics, UB School of Medicine and Biomedical Sciences. "This represents a relative 9.2 percent increase over five years of the study.
"This increase in obesity is important to the obstetrician and the patient because obesity can be a high-risk situation in a pregnant woman," said Yeh. "Obese patients who become pregnant are at increased risk of developing gestational diabetes, pregnancy-related hypertension, preeclampsia, neonatal death and labor complications."
The researchers analyzed data from the Western New York Perinatal Data System, which contains information on more than 200 demographic, obstetric, medical and other items on each delivery occurring in the 17 hospitals in the region with obstetric services.
A breakdown of data showed that 75 percent of the women were between the ages of 20 and 34; 80 percent were white, 55 percent had more than a high school education and 58 percent had HMOs as their insurance carrier.
It was the first live birth for 39 percent of the women, 64 percent lived in urban areas and 80 percent were non-smokers.
While half of the total number of women had a body mass index in the normal range, more than a quarter were obese when they became pregnant. Over five years the percentage of women with a normal BMI dropped from 50.8 percent in 1999 to 49.2 percent in 2003.
During the same time period, the number of overweight women increased from 13.2 percent to 14.6 percent, and the number of obese women increased from 25.1 percent to 25.9 percent.
Preeclampsia poses a serious health threat to the overweight or obese mother, and if not treated properly can result in death of both mother and baby. Preeclampsia causes blood vessels to constrict, resulting in high blood pressure and a decrease in blood flow that can affect many organs, including the liver and kidneys. Less blood flows to the placenta, which can result in poor fetal growth, decreased amniotic fluid and separation of the placenta from the uterine wall before delivery.
Gestational diabetes, while less serious, is an increase in blood sugar during pregnancy that returns to normal after delivery but increases the mother's risk of developing Type 2 diabetes later in life.
Yeh noted that many women gain additional weight during pregnancy, and these pounds often stay with them after the baby is born. "This increases a woman's risk of obesity-related morbidity in the future," he said James A. Shelton, M.S., UB clinical assistant professor of gynecology-obstetrics, is co-author on the study. The research was supported in part by a grant from the New York State Department of Health.