High birth weight is associated with a higher body mass index (BMI) -- a measurement of height and weight -- later in life. However, researchers were not clear whether weight gain during pregnancy contributed to a child’s risk of obesity independently of genetics. Earlier research suggests maternal weight is more strongly associated with a child’s BMI than paternal weight, indicating that pregnancy, not only genetics, may play a key role in a child’s weight.
Researchers at Children’s Hospital in Boston and Columbia University in New York looked at multiple single pregnancies in the same mother to assess the effects of maternal weight gain and to exclude the effects of weight gain from genetic components.
The authors found a consistent connection between weight gain during pregnancy and bigger babies. Among their findings reported in the Aug. 5 issue of The Lancet:
- For every kilogram (kg) a mother gained (1 kg = 2.2 lbs), the baby’s birth weight increased by 7.35 grams (0.25 oz).
- Compared with infants born to women who gained between 8 kg and 10 kg (17.5 and 22 lbs), infants born to mothers who gained more than 24 kg (52.5 lbs) during pregnancy were about 150 g (5.3 oz) heavier at birth.
- Mothers who gained more than 24 kg during pregnancy were more than twice as likely to deliver a baby weighing 4,000 grams (8 lbs 13 oz) or more, compared with women who gained only 8 kg to 10 kg.
The findings are based on state birth registry data from Michigan and New Jersey. Researchers analyzed information on 513,501 women and their 1,164,750 children born between January 1989 and December 2003. Pregnancies shorter than 37 weeks or more than 41 weeks, women who had diabetes, infants born weighing less than 500 grams or more than 7,000 grams, and anyone missing data for pregnancy weight gain were excluded from the study. The study was supported by the National Institutes of Health.
A Look at Childhood Obesity
Childhood obesity has more than tripled in the past 30 years, according to the CDC. From 1980 to 2008, the prevalence of obesity among children aged 6 to 11 jumped from 6.5% to 19.6%; for those aged 12 to 19, those figures increased from 5% to 18.1%, respectively.
Obesity is a major risk factor for several chronic conditions, including cardiovascular disease, cancer, even arthritis. There is a growing interest in the fetal origins of disease that occur later in life, including obesity. The authors suggest that pregnant women may benefit from weight management and prevention strategies to help reduce the risk of weight gain in their children.
“Because high birth weight predicts BMI later in life, these findings suggest that excessive weight gain during pregnancy could raise the long-term risk of obesity-related disease in offspring,” the authors write. “High birth weight might also increase risk of other diseases later in life, including asthma, atopy, and cancer.”
In an accompanying editorial, Neal Halfon and Michael C. Lu from the Center for Healthier Children Families Communities at the University of California in Los Angeles write that “although a better understanding of the effect of gestational weight gain on the developing fetus and metabolic functioning of the newborn child is important, research is urgently needed into how to help women of reproductive age attain and maintain a healthy weight before and during pregnancy. With a growing focus on preconceptional health, there is an opportunity to develop effective interventions to help women conceive at a healthier weight. More effective population-based strategies are needed to produce healthier life-long weight trajectories, and to interrupt the cross-generational cycle of excessive weight gain.”