Several large-scale cohort studies suggest that obese mothers are at increased risk of having infants with neural tube defects and, possibly, other central nervous system (CNS) birth defects. Because obesity and diabetes share similar metabolic abnormalities, a study was planned to determine whether gestational diabetes influences the association between maternal obesity and CNS birth defects. In this population-based case-control study, covering the years 1997 to mid-2000, structured telephone interviews were conducted with mothers of offspring having anencephaly (n ϭ 120), spina bifida (n ϭ 184), holoprosencephaly (n ϭ 49), or isolated hydrocephaly (n ϭ 124). Control women whose infants were neurologically normal were randomly chosen from the same hospitals. Approximately 60% of both cases and control subjects responded. Maternal obesity was defined as a body mass index of 30 kg/m 2 or higher.Pregestational diabetes, both type 1 and type 2, correlated closely with holoprosencephaly (adjusted odds ratio [OR], 47; 95% confidence interval [CI],, and isolated hydrocephaly (OR, 12; 95% CI, 2.9-47). There was no increase in the risk of anencephaly or spina bifida.Gestational diabetes increased only the risk of holoprosencephaly (OR, 2.9; 95% CI, 1.0-8.4). Mothers of infants with anencephaly were less likely than control mothers to have gestational diabetes. Obese mothers were likelier than control subjects to have infants with any of the 4 CNS birth defects. Underweight women were less likely to have an infant with spina bifida. The association between maternal obesity and an increased risk of neural tube defects and isolated hydrocephaly held for all ethnic groups. Associations between maternal obesity and anencephaly (OR, 2.3; 95% CI, 1.2-4.3), spina bifida (OR, 2.8; 95% CI, 1.7-4.5), and isolated hydrocephaly (OR, 2.7; 95% CI, 1.5-5.0) persisted after adjusting for maternal age, ethnicity, education, smoking, alcohol use, and periconceptional vitamin use. For both spina bifida and holoprosencephaly, the joint effects of maternal obesity and gestational diabetes appeared to be interactive.These findings suggest that gestational diabetes and maternal obesity may increase the risk of CNS birth defects through common mechanisms, and they strongly support the need for ways of preventing these conditions. EDITORIAL COMMENT(The epidemic of obesity is worldwide. The prevalence of a body mass index (BMI) Ն30 kg/m 2 in women 18 years of age and older increased from 12% to 18% from 1991 to 1998 (Mokdad AH, et al. JAMA 1999282:1519). The relationship between obesity and diabetes is well known. Does the combination increase the risk of congenital malformations? To investigate the risk of neural tube defect (NTD)-affected pregnancies among obese women (BMI Ն29 kg/m 2 ) compared with women of average prepregnancy weight, Shaw performed a population-based case-controlled study of all hospitals in 55 of 58 counties in California. Compared OBSTETRICSVolume 60, Number 6 OBSTETRICAL AND GYNECOLOGICAL SURVEY ABSTRACTThe major concern...

Low-impact exercise during pregnancy-a study of safety.

Background. Exercise is an important part of many women's lives. Women are often advised to refrain from physical exercise during pregnancy. The reason given is mainly safety, i.e. fear of maternal hyperthermia, which is known to be related to neural tube defects. However, exercise during pregnancy has not been shown to be related to hyperthermia. Objective. To study temperature and oxygen saturation responses to low-impact exercise in healthy pregnant women. Methods. Forty pregnant women and 11 controls participating in low-impact aerobic exercise were monitored before exercise, at maximum-exercise level, and after exercise with regard to core temperature, heart rate, and oxygen saturation level. Results. The core temperature among the pregnant women did not increase significantly at maximum exercise or after exercise (36.5 versus 36.7 or 36.5 C, P ¼ 0.1, P ¼ 0.5). None of the pregnant women were even close to approaching a dangerous body temperature at an intensity level of 69% of their maximum heart rate. As compared with pre-exercise values, oxygen saturation among pregnant women was significantly reduced at both maximum-exercise and postexercise measurements, but no measurement was below 95% in oxygen saturation. Conclusion. Low-impact aerobics at about 70% of one's maximum heart rate appears to be safe in terms of risk of maternal hyperthermia.

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The most common form of Down's syndrome is due to an extra chromosome No. 21, i.e. three instead of two chromosomes 21, Trisomy 21 (T21). This was discovered over 50 years ago. We now know with certainty that the extra chromosome usually comes from the mother (in approximately 19 out of 20 cases) and also that the probability of having a child with Down's syndrome increases with maternal age. However, we still do not know how this comes about.