Growing fat in utero: timing is everything

Is the Biphasic Effect of Diabetes and Obesity on Fetal Growth a Risk Factor for Childhood Obesity?

In pregnancies of women with obesity or diabetes, neonates are often overgrown. Thus, the pregnancy period in these women offers a window of opportunity to reduce childhood obesity by preventing neonatal overgrowth. However, the focus has been almost exclusively on growth in late pregnancy. This perspective article addresses possible growth deviations earlier in pregnancy and their potential contribution to neonatal overgrowth. This narrative review focuses on six large-scale, longitudinal studies that included ∼14,400 pregnant women with at least three measurements of fetal growth. A biphasic pattern in growth deviation, including growth reduction in early pregnancy followed by overgrowth in late pregnancy, was found in fetuses of women with obesity, gestational diabetes mellitus (GDM), or type 1 diabetes compared with lean women and those with normal glucose tolerance. Fetuses of women with these conditions have reduced abdominal circumference (AC) and head circumference (HC) in early pregnancy (observed between 14 and 16 gestational weeks), while later in pregnancy they present the overgrown phenotype with larger AC and HC (from approximately 30 gestational weeks onwards). Fetuses with early-pregnancy growth reduction who end up overgrown presumably have undergone in utero catch-up growth. Similar to postnatal catch-up growth, this may confer a higher risk of obesity in later life. Potential long-term health consequences of early fetal growth reduction followed by in utero catch-up growth need to be explored.

Gestational Diabetes Mellitus and High Triglyceride Levels Mediate the Association between Pre-Pregnancy Overweight/Obesity and Macrosomia: A Prospective Cohort Study in Central China

The purpose of this study is to investigate whether the link between pre-pregnancy overweight/obesity and risk of macrosomia is mediated by both gestational diabetes mellitus (GDM) and high maternal triglyceride (mTG) levels. This prospective study finally included 29,415 singleton term pregnancies. The outcome of interest was macrosomia (≥4000 g). High mTG levels were denoted as values ≥90th percentile. GDM was diagnosed using a standard 75 g 2 h oral glucose tolerance test. The mediation analysis was conducted using log-binomial regression while controlling for maternal age, education, parity, gestational weight gain, gestational hypertension, smoking, drinking and infant sex. Overall, 15.9% of pregnant women were diagnosed with GDM, and 4.3% were macrosomia. Mediation analysis suggested that overweight had a total effect of 0.009 (95% CI, 0.006–0.013) on macrosomia, with a direct effect of 0.008 (95% CI, 0.004–0.012) and an indirect effect of 0.001 (95% CI, 0.001–0.002), with an estimated proportion of 11.1% mediated by GDM and high mTG levels together. Furthermore, we also discovered a total effect of obesity on macrosomia of 0.038 (95% CI, 0.030–0.047), consisting of a direct effect of 0.037 (95% CI, 0.028–0.045) and an indirect effect of 0.002 (95% CI, 0.001–0.002), with an estimated proportion of 5.3% mediated by GDM and high mTG levels combined. Both GDM and high mTG levels enhanced the risk of macrosomia independently and served as significant mediators in the relationship between pre-pregnancy overweight/obesity and macrosomia.

Appropriate Timing of Gestational Diabetes Mellitus Diagnosis in Medium- and Low-Risk Women: Effectiveness of the Italian NHS Recommendations in Preventing Fetal Macrosomia

BACKGROUND

Screening strategies for gestational diabetes mellitus (GDM) earlier than 24-28 weeks of gestation should be considered to prevent adverse pregnancy outcomes. Nonetheless, there is uncertainty about which women would benefit most from early screening and which screening strategies should be offered to women with GDM. The Italian National Healthcare Service (NHS) recommendations on selective screening for GDM at 16-18 weeks of gestation are effective in preventing fetal macrosomia in high-risk (HR) women, but the appropriateness of timing and effectiveness of these recommendations in medium- (MR) and low-risk (LR) women are still controversial. Patients and Methods. We retrospectively enrolled 769 consecutive singleton pregnant women who underwent both anomaly scan at 19-21 weeks of gestation and screening for GDM at 16-18 and/or 24-28 weeks of gestation, in agreement with the NHS recommendations and risk stratification criteria. Comparison of maternal characteristics, fetal biometric parameters at anomaly scan (head circumference (HC), biparietal diameter (BPD), abdominal circumference (AC), femur length (FL), estimated fetal weight (EFW)), and neonatal birth weight (BW) percentile among risk groups was examined.

RESULTS

219 (28.5%) women were diagnosed with GDM, while 550 (71.5%) were normal glucose-tolerant women. Out of 164 HR women, only 62 (37.8%) underwent the recommended early screening for GDM at 16-18 weeks of gestation. AC and EFW percentiles, as well as neonates' BW percentiles, were significantly higher in HR women diagnosed with GDM at 24-28 weeks of gestation with respect to normal glucose-tolerant women, as well as MR and LR women who tested positive for GDM. Comparative analysis between MR and LR women with GDM and women with normal glucose tolerance revealed significant differences in both AC and EFW percentiles (P < 0.05), while there was no significant difference in neonatal BW percentiles.

CONCLUSION

In MR and LR women with GDM, a mild acceleration of fetal growth can be detected at the time of anomaly scan. However, in these at-risk categories, the NHS recommendations for screening and treatment of GDM at 24-28 weeks of gestation are still effective in normalizing BW and preventing fetal macrosomia, thus supporting a risk factor-based selective screening program for GDM.