Pregnancy is a time of great expectation and joy, but it also brings its own set of problems. Gestational diabetes mellitus (GDM) is one condition that appears or is first recognized during pregnancy as glucose intolerance. It complicates up to a fourth of pregnancies worldwide, though this rate varies widely with the location.
A new study aims to explore the use of adiposity measures as a method to assess the relative efficacy of weight gain and GDM interventions in pregnancy.
Protocol: Differential effects of diet and physical activity interventions in pregnancy to prevent gestational diabetes mellitus and reduce gestational weight gain by level of maternal adiposity: a protocol for an individual patient data (IPD) meta-analysis of randomised controlled trials. Image Credit: Image Point Fr / Shutterstock
The screening and diagnosis of GDM remains controversial, with different professional societies recommending different guidelines. For instance, the UK screens all women with risk factors for the condition between 24-28 weeks, except for those who had GDM in a prior pregnancy. These women are screened at or before ten weeks, if possible.
In contrast, the USA, Australia, and Canada screen all women during pregnancy but use different strategies and varying cut-offs. This is a significant issue given that GDM affects both the mother and the infant over the short and long term.
Why is GWG important?
While pregnant women should ideally gain weight, the extent of gestational weight gain (GWG) may also affect the health of both mother and fetus or infant if excessive. Unfortunately, about half of pregnant women have excessive weight gain, and this only increases to about 60% with pre-existing obesity.
High GWG is linked to excessive weight gain in childhood and adolescence, with a 40% increase in the risk of overweight or obesity by 2-5 years, going up to an increase in risk by 72% by 10-18 years. Obesity in pregnancy is therefore followed up with GDM screening and monitoring for pre-eclampsia as well as fetal growth, along with advice on diet and physical activity.
Is BMI an adequate marker?
Given the importance of obesity in pregnancy, there is a need for more work to predict the individual risk for obesity in this population. Scientists are trying to identify better tools than the BMI, which fails to record the pattern of fat deposition, a crucial factor in predicting morbidity and metabolic dysregulation connected with obesity.
The BMI is poorly correlated with obesity, as well. Prior studies showed that approximately half and 40% of women with a high and borderline BMI had complicated pregnancies, respectively.
“This suggests that BMI is not adequately identifying all women who would benefit most from diet and/or physical activity weight management interventions, and some women are receiving expensive and time-consuming additional care that is not required.”
Adiposity rather than BMI to predict GWG
Adiposity is more important than BMI in predicting the risk of GDM. Markers such as the waist circumference or waist-to-hip ratio could be more important in targeting pregnant women at increased risk of adverse outcomes. This could in turn, help healthcare providers to direct their guidance on weight management in a clinically appropriate fashion compared to the BMI.
Earlier large meta-analyses and reviews of meta-analyses suggest a consistent reduction of GWG with weight management measures. For example, one study indicated a loss of 0.7 kg compared to controls. However, this increased to -1.1 kg when all study data was incorporated.
The range of reduction in GWG is from -2 kg to ~-6 kg, with either type of intervention, alone or in combination, though the most significant reduction is seen with diet-only measures. Women with a high BMI had the largest reductions in GWG.
Unfortunately, the BMI did not show any significant effect on GDM incidence following different modes of weight management, viz., diet vs. exercise. The results are conflicting, perhaps due to differences in study design and mode or content of interventions.
In the current study, as reported in the journal BMJ Open, this data will be reanalyzed using adiposity measures. Both the GDM and GWG will be analyzed as outcomes that help to measure the efficacy of weight management programs or plans. These will be targeted at women with early pregnancy obesity.
The overall effects of these interventions will be reported and then linked with the different adiposity measures to examine the presence of correlations. The study will be based on individual patient data (IPD). The researchers will conduct a meta-analysis to examine whether and how weight gain in pregnancy could be targeted using adiposity measures other than the body mass index (BMI).
The researchers will attempt to compensate for study heterogeneity, missing data, and other sources of bias.
“This research aims to address a gap in the knowledge and is completely novel; in terms of the targeting interventions in pregnancy based on alternative measures of adiposity to BMI for the prevention of GDM and reduction of GWG.”
Furthermore, the results could help to shape future guidelines in preventing GDM and managing GWG in pregnancy by looking at the utility of individual adiposity data rather than BMI as selectors for targeted interventions.
If these data are found to be useful, future research would be required to assess the cost-effectiveness of such interventions in pregnancy, given that “women with overweight and obesity in pregnancy have increased service usage and costs of 23% and 37%, respectively.”