Non classical risk factors for gestational diabetes mellitus: a systematic review of the literature.

Age, obesity and family history of diabetes are well known risk factors for gestational diabetes mellitus. Others are more controversial. The objective of this review is to find evidence in the literature that justifies the inclusion of these other conditions among risk factors. The MEDLINE, Cochrane, LILACS and Pan American Health Organization databases were searched, covering articles dating from between 1992 and 2006. Keywords were used in combination (AND) with gestational diabetes mellitus separately and with each one of the risk factors studied. The methodological quality of the studies included was assessed, resulting in the selection of 41 papers. Most studies investigating maternal history of low birth weight, low stature, and low level of physical activity have found positive associations with gestational diabetes mellitus. Low socioeconomic levels, smoking during pregnancy, high parity, belonging to minority groups, and excessive weight gain during pregnancy presented conflicting results. Publication bias cannot be ruled out. Standardization of techniques, cutoff points for screening and diagnosis, as well as studies involving larger sample sizes would allow future meta-analyses.