In the current study, we found a high prevalence of maternal obesity and GDM among Saudi women: 47.8% and 50.2%, respectively. This is consistent with a study from Riyadh in which the prevalence of obesity was 44% among Saudi pregnant women. In contrast, the prevalence of GDM was 15% in that study, which is much lower than the rate in this study . The marked difference in GDM prevalence between the two studies is mostly related to the different methods used for GDM diagnosis. While the IADPSG criteria were used in the current study, Wahabi et al.  used the Carpenter and Coustan criteria . This finding was demonstrated in our previous study that assessed the prevalence of GDM when applying the IADPSG vs. the Carpenter and Coustan criteria, which revealed a 2.44-fold (144.6%) increase when applying the IADPSG criteria: 41.5% vs. 16.9%, respectively. This is also consistent with the findings from other studies , .
In the present study, the combination of maternal obesity and GDM affected one-third of women and was associated with older maternal age, higher weight and more adverse pregnancy outcomes than each condition alone. This is in concordance with many previous studies –.
The mean birth weight increased in order among the four groups; it was highest in the infants in the obese GDM group, followed by those in the obese non-GDM, GDM nonobese, and reference groups. However, significance was only reached when the infants in the obese GDM group were compared to the infants in the GDM nonobese and reference groups, with 217 and 291 gm differences, respectively. This is consistent with the findings from other studies , , .
The risk of macrosomia and cesarean delivery were significantly increased in all three groups in comparison to that in the reference group. There was a tendency toward a higher risk of macrosomia among infants of obese women with and without GDM than among infants in the nonobese GDM group; however, the result did not reach significance. In the Finnish study, the risk of macrosomia and cesarean delivery were increased in obese women without GDM, and coexistent GDM increased the risk to a greater degree. However, normal-weight women with GDM were similar to normal-weight women without GDM . Similarly, Ricart et al. found that obesity influenced macrosomia and cesarean section rates more than GDM . Although the risk of cesarean delivery was found to be associated more with obesity than GDM in the HAPO study, macrosomia was associated more with GDM than obesity. This contradicting finding is possibly attributed to the lack of medical interventions for mild GDM in that study .
The rate of admission to the NICU was higher in infants in all three groups than in those in the reference group but only reached significance in GDM groups with and without obesity. This is in line with the findings from previous studies , . The routine monitoring of infants of GDM mothers due to the concern of neonatal hypoglycemia and close observation of the infants’ blood sugar may contribute to the increased risk of NICU admission. Nonetheless, in the Finnish study, the risk of NICU admission remained elevated in the infants of mothers with GDM after adjustment for neonatal hypoglycemia .
The rate of low Apgar score was significantly higher in the infants of obese GDM women than in the infants of the reference group. In addition, there was a tendency toward a low Apgar score in the GDM nonobese group in comparison to the scores in the obese non-GDM group and the reference groups; however, the findings did not reach significance. This result is consistent with the findings of the Wahabi et al. and Finnish studies , . Although Hildeń et al. found that maternal obesity and GDM are major independent risk factors for a low Apgar score, no interaction effect between GDM and obesity was found .
From the findings of the current study and others, one can extrapolate that obesity is associated with a higher birth weight and greater risk of macrosomia and cesarean delivery than GDM. On the other hand, GDM is associated with a greater risk of low Apgar score and admission to the NICU. However, the combination of obesity and GDM is associated with the greatest risk of adverse pregnancy outcomes , , .
Although obesity is recognized to adversely affect pregnancy, there are no recommendations from professional organizations that endorse the consideration of obesity during pregnancy. Maternal obesity should indicate a high-risk pregnancy, particularly if combined with GDM. Until professional guidelines become available, lifestyle interventions, including diet and physical activity, should be recommended for obese women during pregnancy. Weight monitoring during pregnancy is required to avoid excessive weight gain. Women of reproductive age with obesity should receive facts and advice about the risks of obesity during pregnancy and be recommended to lose weight before and between pregnancies .
Limitations of the present study include the lack of data on prepregnancy maternal weight, which might be a contributing factor to the higher rate of obesity in this cohort of participants. However, we had the chance to measure weight at the first antenatal visit, which should not vary significantly from the prepregnancy weight. Another limitation was that no intervention was provided to the obese non-GDM group, which may contribute to the higher rate of increased birth weight of the infants in this group; however, this is the usual practice. The strength of this study is that it is prospective, so we had the chance to ensure the maintenance of good glycemic control among women with GDM. In addition, an OGTT was performed on all participants, so no woman with GDM was missed.