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Two well-designed large prospective randomized controlled studies have confirmed that diagnosis and treatment of GDM have short-term benefits for both mother and baby [40, 41]. Women in the Australian (Crowther) study had early pregnancy BMIs ranging from 22.9 to 31.2 kg/m², and women in the intervention arm of the study had lower weight gain during pregnancy, with less macrosomia, less LGA, and lower rates of preeclampsia [40]. In the US (Landon) study, the BMI at recruitment of women in the treatment arm was 30.1 ± 5 kg and control arm 30.2 ± 5.1 kg. Once again, in this study, women in the intervention arm had lower weight gain; there were lower rates of LGA and macrosomia in infants, and women had lower rates of preeclampsia [41].

There are now 2 additional large trials sufficiently powered to examine maternal and perinatal outcomes after a lifestyle intervention in overweight and obese women and the results of this study: the “LIMIT” study [42] and the “UPBEAT” study [43], both of which failed to show major benefits for well-structured lifestyle interventions. Essentially, these studies aimed to limit weight gain in overweight and obese pregnant women through lifestyle intervention. Neither study found a difference in rates of GDM or infants born LGA, although the LIMIT study did report a reduction in infants weighing over 4,000 g.

Fig. 2. Mechanisms linking obesity with accompanying hyperglycemia to excess fetal growth.

The Vitamin D and Lifestyle Intervention for GDM prevention (DALI) study [44], conducted in 11 centers across 9 European countries, recently examined the effectiveness of 3 differing lifestyle interventions (healthy eating [HE], physical activity [PA], and HE + PA) as compared to usual care, in an attempt to prevent GDM in obese women. The HE + PA combined intervention reduced GWG (–2.02 kg; 95% CI –3.59 to –0.46 kg), but failed to reduce GDM prevalence or improve fasting or post load glucose values on the diagnostic OGTT. The frequency of LGA and SGA babies was not altered by any treatment.

A recent randomized controlled trial in 300 women reported that supervised aerobic exercise from 10 weeks gestation prevented GDM [45]. Compared to previous exercise studies in this group of patients, this study was of moderate intensity, commenced at an earlier gestation, had an impact on reducing weight gain by 25 weeks gestation, and had reasonable compliance. It was also reassuring as there was no increase in preterm birth in the intervention arm. However, birth weight was reduced in the intervention arm, and this is an issue that needs to be examined with long-term infant follow-up. This study warrants replication in other populations and to assess whether it is generalizable to the broader population.

A recent individual patient data meta-analysis has been published by the International Weight Management in Pregnancy Collaborative [46]. This report found that diet and exercise interventions reduce cesarean section rate and weight gain during pregnancy. There was an impact on important maternal or neonatal clinical outcomes, although the longer term health impacts of these studies are not known. Importantly, obese women are no more or less likely to benefit from these interventions than lean or overweight women. Lastly, these interventions were not found to be cost-effective. Other recent systematic reviews have shown divergent results. The most recent Cochrane review of combined diet and exercise interventions in pregnancy suggested a possible reduction in GDM (relative risk 0.85, 95% CI 0.71–1.01) but no difference in LGA or hypertensive disorders of pregnancy [47]. Similar results were reported by the Cochrane review group for dietary interventions alone [48]. Another recent systematic review, including a number of studies from China [49], concluded, counterintuitively, that single component diet and PA interventions aimed at reducing GWG reduced GDM but that combined interventions did not.

Given the large number of studies regarding lifestyle intervention in obese pregnant women, and the disappointing outcomes of these studies, alternative approaches must clearly be sought and we must consider why current interventions are of only marginal value.

A variety of explanations should be considered. While changes in diet and exercise have undoubtedly contributed to the increasing struggle with overweight and obesity in women of reproductive age, it is highly likely that other factors also contribute. The complex range of contributors to overweight and obesity are increasingly recognized and may give clues to more holistic approaches to care in the future [50–52].

As the obesity epidemic has evolved, other aspects of the lives of women in their reproductive years have also utterly changed [53]. Working motherhood is now the norm, with less time for self-care and infant care and breastfeeding. There is clear epidemiological evidence that a range of factors contribute to obesity including sleep debt, ambient temperature, technology, pharmaceutical iatrogenesis, endocrine disruptors, gut microbiome, economic disparity, and the intrauterine transgenerational effects of increasing maternal age and increasing maternal BMI [52]. The research outlined above has focused on factors that are within the capacity of the individual to control (food and exercise), and represent the “hegemony of the big two” without fully appreciating the complex contributors to this epidemic. Given this narrow focus, the disappointing results of interventions targeting the “big two” [54] are perhaps predictable. Future intervention studies need to examine to what extent intervention in the complex mix of factors, including interventions to address sleep, screen time, medications, the gut microbiota, psychological factors, support for breastfeeding, and other supports might assist in preventing adverse pregnancy and neonatal outcomes in obese women.

Until a more holistic approach to management has research to guide it, the best options at present appear to be in relation to diagnosing and treating GDM in overweight and obese women. Lifestyle interventions have a modest impact on limiting GWG [46], with less convincing data regarding preventing overall maternal adverse outcomes and preventing neonatal adverse outcomes. Further, it is important to note that the long-term impacts of any of these interventions on the health of adult offspring are as yet unproven and will need to be carefully examined.