HHEX and gestational diabetes: Emerging data show that prior GDM episodes constitute a strong risk factor for insulin therapy during the index pregnancy.12 A study found that GDM reoccurred in nearly half of women with a known history of GDM.31 Recurrent GDM may be due to a genetic predisposition, as several genes have been associated with GDM susceptibilities such as CDKAL1 and CDKN2A/2B, HHEX, IGF2BP2, SLC30A8, and TCF7L2.