Low Birth Weight as a Risk Factor for Gestational Diabetes, Diabetes, and Impaired Glucose Tolerance During Pregnancy

Table 1 presents results of studies presenting data on a woman's birth weight as a risk factor for GDM (14–21). Several of the studies are population studies that present the prevalence of GDM by birth weight (14–18), whereas others present the birth weight frequency distributions of women with and without GDM (19,20). These studies all found that the prevalence of GDM was higher in women who were in the lower birth weight category or categories. A significant relationship between a low birth weight and gestational or pregestational diabetes has been described among Native American women in Arizona and Washington State, among African-Americans and Hispanics in Washington and New York State, and among non-Hispanic whites from Washington, New York, Norway, Italy, Australia, and Malta (14–21). Interestingly, several studies (15–17,19), in addition to the Pima study (14), described a U-shaped association between birth weight and GDM (Fig. 1). The article by Moses et al. (21) reports, among women with GDM, that the mean 2-h glucose concentration at the diagnosis of GDM is associated with that woman's birth size. Women who had been small for gestational age at birth had a 2-h glucose concentration that was significantly higher than women who had been of normal weight for gestational age (21). There was a tendency for women who had been large for dates to have a higher glucose as well, suggesting a U-shaped association, but this difference was not significant.

With the large number of reports in nonpregnant populations that low birth weight is a risk factor for the later development of diabetes at young ages, it was to be expected that it might also be a risk factor for GDM. As shown in this article, this has been a common finding, and several studies, some of them with very large sample sizes, have provided confirmation. Of interest is that several reported a U-shaped association with birth weight—a finding that has been uncommon in nonpregnant populations. These studies, the Pima Indian study, and the Taiwanese schoolchildren survey all share a young age of onset of diabetes. For decades, the Pima Indians have developed diabetes at relatively young ages (22). Today, type 2 diabetes is being found increasingly in younger members of other populations as well (23). GDM, since it is a condition of women of childbearing age, also develops at a relatively young age. One reason may be that for young people today, a large birth weight was more likely due to an abnormality during pregnancy, such as maternal diabetes in the case of the Pima Indians (5,22), that puts them at high risk for developing diabetes in contrast to the past when a large birth weight was more likely associated with overall general health of the mother and child and therefore was not a risk factor. The future may prove that this finding becomes more common in the general population over time. In particular, additional surveys similar to the Taiwanese study that relate childhood-onset type 2 diabetes to birth weight should be undertaken to provide more insight into this question.

Universal screening for GDM was the recommendation of the American Diabetes Association from 1979 (24) until 1998 (25). The participants at the 4th International Workshop-Conference on Gestational Diabetes recommend that women who met certain characteristics (member of low-risk ethnic group, no known diabetes in first-degree relatives, age <25 years, normal weight, no history of abnormal glucose tolerance, and no history of poor obstetric outcomes) did not have to be screened routinely (25). Although this recommendation has not been universally accepted (26–31), for those who do follow these guidelines, a normal birth weight should be included in the list of characteristics a woman must possess to be exempt from routine screening.

In summary, women from diverse populations who were of low birth weight are at risk for the development of GDM. This observation is not surprising given the well-described health consequences of abnormal fetal growth that are apparent in very young children and persist into adulthood. Unlike the preponderance of reports among the nonpregnant population, during pregnancy, the risk for GDM is likely to have a U-shape, with excess disease developing in women whose own birth weights were either very high or very low.