Public Release: 

Tracking premature babies: girls grow bigger than boys

University Hospitals of Cleveland

CLEVELAND, July 7, 2003: After tracking the physical growth rates of very premature babies over a 20-year period, researchers have discovered that male premature babies lag behind their female counterparts, while the young women not only catch up in weight and height to their normal birth weight counterparts but also exhibit similar rates of obesity. This rapid growth seen when children "catch up" places them at risk for type two diabetes and its health-related problems later in life. The research team was led by noted neonatologist Maureen Hack, MD, at Rainbow Babies & Children's Hospital, part of University Hospitals Health System (UHHS), and Case Western Reserve University (CWRU).

Published in the July 2003 issue of the journal Pediatrics, the study is the first report of the gender specific outlook for growth of very low birth weight infants born during the early years of neonatal intensive care (1977-1979) and followed into young adulthood. "Though advances in neonatal intensive care have significantly increased survival rates, complications of prematurity have not changed," says Dr. Hack, neonatologist at UHHS Rainbow Babies & Children's Hospitals and professor of neonatology at CWRU, "Neonatal growth failure continues to be a major problem, especially among the smallest and sickest infants. Thus, our findings have relevance to current survivors of severe prematurity."

The infants studied included 103 males and 92 females, born at a mean gestational age of 29.8 weeks (considered very premature in the late 1970s). None of them suffered from neurosensory impairment, though the male babies were significantly more likely to be hospitalized during infancy for various ailments. Both males and females has significant lower weight, height and body mass index at the age of eight compared to normal controls, but during the next 12 years, the girls caught up with their normal birth weight counterparts.

"Though we like to see these premature babies grow into physically healthy adults, we were concerned about the levels of obesity among the very low birth weight female babies once they reached age twenty," says Dr. Hack. "As a group, these women caught up in weight more than in height, 21% of them were overweight and 15% of them obese by the age of 20. Of course, there is growing evidence that children who grow rapidly during childhood are more likely to be obese as adults and at risk for metabolic disturbances such as insulin resistance and type II diabetes, and for hypertension and cardiovascular disease."

Dr. Hack noted that it is important to continue to follow this group of babies into mature adulthood to fully appreciate the long-term metabolic and cardiovascular implications of the rapid growth of these premature female infants.


Dr. Hack's research was supported by grants from the National Institutes of Health, and the Genentech Foundation for Growth and Development.

University Hospitals Health System (UHHS) is the region's premier healthcare delivery system, serving patients at more than 150 locations throughout northern Ohio.

The System's 947-bed, tertiary medical center, University Hospitals of Cleveland (UHC), is the primary affiliate of Case Western Reserve University (CWRU). Together, they form the largest center for biomedical research in the State of Ohio. The System provides the major clinical base for translational researchers at the Case Research Institute, a partnership between UHC and CWRU School of Medicine, as well as a broad and well-characterized patient population for clinical trials involving the most advanced treatments. Included in UHC are Rainbow Babies & Children's Hospital, among the nation's best children's hospitals; Ireland Cancer Center, northern Ohio's only National Cancer Institute-designated Comprehensive Cancer Center (the nation's highest designation); and MacDonald Women's Hospital, Ohio's only hospital for women.

Committed to advanced care and advanced caring, University Hospitals Health System offers the region's largest network of primary care physicians, outpatient centers and hospitals. The System also includes a network of specialty care physicians, skilled nursing, elder health, rehabilitation and home care services, managed care and insurance programs, and the most comprehensive behavioral health services in the region. For more information, go to

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