Kaiser Permanente Study Shows Overweight and Obese Women more Likely to have Large Babies

PASADENA, Calif. – Women who are overweight or obese are more likely to deliver infants who are large for their gestational age at delivery, regardless of whether they develop gestational diabetes during their pregnancy, according to a study by Kaiser Permanente published today in Diabetes Care.

Among pregnant women who did not develop gestational diabetes, overweight women were 65 percent more likely, and obese women 163 percent more likely, to have overly large babies than their healthy-weight counterparts. In this study, an overly large infant was identified based on having a birth weight over the 90th percentile for its gestational age at delivery and gender. Gaining excess weight during pregnancy also contributed to having a large-for-gestational-age baby, regardless of maternal weight or whether the mother developed gestational diabetes.

This Kaiser Permanente study of nearly 10,000 pregnant women from Kaiser Permanente Southern California examined adverse outcomes among women with and without gestational diabetes, as defined by the recently established International Association of Diabetes and Pregnancy Study Groupsguidelines. Overly large babies are at increased risk for birth complications and for being overweight or obese later in life.

Unhealthy pre-pregnancy body weight, gestational diabetes and excess weight gain during pregnancy are all contributors to problems during pregnancy and at delivery, said study lead author Mary Helen Black, PhD, of Kaiser Permanente Southern California’s Department of Research & Evaluation. It’s possible that a large percentage of these problems may be prevented by helping overweight or obese women lose weight before they become pregnant or control their weight gain during pregnancy. Future intervention studies are needed to substantiate this.

Researchers examined the electronic health recordsof 9,835 women who received prenatal care and delivered their babies at the Kaiser Permanente Southern California Downey Medical Center(formerly called Bellflower Medical Center) over a five-year period from Oct. 30, 2005 to Dec. 31, 2010. Sixty percent of these women were overweight or obese and 19 percent developed gestational diabetes.

By losing weight to achieve a healthy weight before pregnancy and by keeping their weight gain during pregnancy within guidelinesestablished by the Institute of Medicine, women may decrease the health risks to their unborn babies and themselves, said study co-author David A. Sacks, MD, adjunct investigator at the Department of Research & Evaluation and a retired obstetrician-gynecologist from the Kaiser Permanente Downey Medical Center. For children of overweight and obese women, the risks include an increased likelihood of having an excessive amount of body fat and being overweight or obese themselves, which can lead to high blood pressure, heart disease and type 2 diabetes later in life.

This study is part of ongoing efforts at Kaiser Permanente to conduct studies and increase public awareness of the prevalence and effects of obesity in the United States. Earlier this year, Kaiser Permanente partnered with HBO (Home Box Office), the Institute of Medicine, the National Institutes of Health, the Centers for Disease Control and Prevention and the Michael & Susan Dell Foundation to launch one of the most ambitious public education campaigns addressing America’s obesity epidemic to date, including the documentary series The Weight of the Nationon HBO.

Kaiser Permanente can deliver transformational health research in part because it has the largest private electronic health record system in the world. The organization’s integrated model and EHR securely connects 9 million people, 533 medical offices, and 37 hospitals, linking patients with their health care teams, their personal health information, and the latest medical knowledge. It also connects Kaiser Permanente’s researchers to one of the most extensive collections of de-identified medical data available, facilitating study and important medical discoveries that shape the future of health and care delivery for patients and the medical community. This research is a part of Kaiser Permanente’s broader efforts to understand, prevent and treat adverse pregnancy outcomes.

Previous Kaiser Permanente research includes:

  • A study of over 11,000 women with gestational diabetes found that referral to a telephone-based nurse management program was associated with lower risk of high baby birth weight and increased postpartum glucose testing (American Journal of Obstetrics and Gynecology, 2012).

  • A study that found a woman’s risk of developing diabetes during pregnancy can be identified up to seven years before she becomes pregnant based on routinely assessed measures of blood sugar and body weight (American Journal of Obstetrics and Gynecology, 2011).

  • A study that found cardio-metabolic risk factorssuch as high blood sugar and insulin, and low high-density lipoprotein cholesterol that are present before pregnancy, predict whether a woman will develop diabetes during a future pregnancy (American Journal of Epidemiology, 2010).

  • A study of 10,000 mother-child pairs that showed treating gestational diabetes during pregnancy can break the link between gestational diabetes and childhood obesity (Diabetes Care, 2007).

  • A study of 1,145 pregnant women that found that women who gain excessive weight during pregnancy, especially in the first trimester, may increase their risk of developing diabetes later in their pregnancy (Obstetrics and Gynecology, 2010).

Additional study authors include: Anny H. Xiang, PhD, and Jean M. Lawrence, ScD, MPH, MSSA, of the Kaiser Permanente Southern California Department of Research & Evaluation.

Kaiser Permanente Southern California Department of Research & Evaluation
The Department of Research & Evaluation conducts high-quality, innovative research into disease etiology, prevention, treatment and care delivery. Investigators conduct epidemiological, health services, and behavioral research as well as clinical trials. Areas of interest include diabetes, obesity, cancer, HIV/AIDS, cardiovascular disease, aging and cognition, pregnancy outcomes, women’s and children’s health, quality and safety, and pharmacoepidemiology. Located in Pasadena, California, the department focuses on translating research to practice to benefit the health and well-being of Kaiser Permanente Southern California members and the general population. Visit

About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America’s leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 9 million members in nine states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: