Maternal Obesity, GDM and Macrosomia
The majority of mothers with GDM are obese, and a significant proportion of those who are obese have GDM [35] . One meta-analysis showed that the risk of developing GDM was 2.14-fold higher in overweight pregnant women, 3.56-fold higher in obese pregnant women and 8.56-fold higher in severely obese pregnant women compared
to pregnant women with normal weight [36] . An analysis of data from more than 23,000 women in the HAPO (Hyperglycemia and Adverse Pregnancy Outcomes study [37] showed that the prevalence of macrosomia among 17,244 nonobese women without GDM was 6.7% compared to 10.2% in 2,791 nonobese women with GDM and 20.2% in 935 obese women with GDM. A study has shown that maternal obesity is a stronger predictor of a large-for-gestational-age infant than maternal
hyperglycemia [38] . In the HAPO study [37], the investigators found that the frequency of macrosomia in GDM was increased by 50% compared to non-GDM in both the nonobese and obese groups. Obesity was associated with a 2-fold higher frequency of macrosomia whether in the non-GDM or GDM group. Macrosomia in GDM only was present in 26%, in GDM plus obesity in 33% and in obesity only in 41%. A large prospective study from Spain found that the upper quartile of maternal BMI was responsible for 23% of macrosomia, while GDM accounted for 3.8% [39] . Women who did not have GDM but who were obese had a 13.6% increased risk of macrosomia (defined as a child weighing 4,000 g or more at birth) than nonobese women [37] .