Mild gestational diabetes: towards a redefined threshold?

Abnormal placental villous maturity and dysregulated glucose metabolism: implications for stillbirth prevention

OBJECTIVES

In the UK one in 250 pregnancies end in stillbirth. Abnormal placental villous maturation, commonly associated with gestational diabetes, is a risk factor for stillbirth. Histopathology reports of placental distal villous immaturity (DVI) are reported disproportionately in placentas from otherwise unexplained stillbirths in women without formal diagnosis of diabetes but with either clinical characteristics or risk factors for diabetes. This study aims to establish maternal factors associated with DVI in relation to stillbirth.

METHODS

Placental histopathology reports were reviewed for all pregnant women delivering at University College London Hospital between July 2018 to March 2020. Maternal characteristics and birth outcomes of those with DVI were compared to those with other placental lesions or abnormal villous maturation.

RESULTS

Of the 752 placental histopathology reports reviewed, 11 (1.5%) were reported as diagnostic of DVI. Eighty cases were sampled for clinical record analysis. All women with DVI had normal PAPP-A (>0.4 MoM), normal uterine artery Doppler studies (UtA-PI) and were normotensive throughout pregnancy. Nearly one in five babies (2/11, 18.5%) with DVI were stillborn and 70% had at least one high glucose test result in pregnancy despite no formal diagnosis of diabetes.

CONCLUSIONS

These findings suggest that the mechanism underlying stillbirth in DVI likely relates to glucose dysmetabolism, not sufficient for diagnosis using current criteria for gestational diabetes, resulting in placental dysfunction that is not identifiable before the third trimester. Relying on conventional diabetes tests, foetal macrosomia or growth restriction, may not identify all pregnancies at risk of adverse outcomes from glucose dysmetabolism.

Mild Gestational Diabetes and Adverse Pregnancy Outcome: A Systemic Review and Meta-Analysis

Background and Objectives: Mild gestational diabetes (GDM) refers to the gestational hyperglycemia, which does not fulfill the diagnostic criteria for GDM. The results of studies on adverse pregnancy outcomes among women with mild GDM are controversial. Therefore, the aim of this systematic review and meta-analysis was to investigate the impact of mild GDM on the risk of adverse maternal and neonatal outcomes. Methods: A thorough literature search was performed to retrieve articles that investigated adverse maternal and neonatal outcomes in women with mild GDM in comparison with non-GDM counterparts. All populations were classified to three groups based on their diagnostic criteria for mild GDM. Heterogeneous and non-heterogeneous results were analyzed using the fixed/random effects models. Publication bias was assessed using the Harbord test. DerSimonian and Laird, and inverse variance methods were used to calculate the pooled relative risk of events. Subgroup analysis was performed based on mild GDM diagnostic criteria. Quality and risk of bias assessment were performed using standard questionnaires. Results: Seventeen studies involving 11,623 pregnant women with mild GDM and 53,057 non-GDM counterparts contributed to the meta-analysis. For adverse maternal outcomes, the results of meta-analysis showed that the women with mild GDM had a significantly higher risk of cesarean section (pooled RR: 1.3, 95% CI 1.2-1.5), pregnancy-induced hypertension (pooled RR: 1.4, 95% CI 1.1-1.7), preeclampsia (pooled RR: 1.3, 95% CI 1.1-1.5) and shoulder dystocia (pooled RR: 2.7, 95% CI 1.5-5.1) in comparison with the non-GDM population. For adverse neonatal outcomes, the pooled relative risk of macrosomia (pooled RR = 0.4, 95% CI: 1.1-1.7), large for gestational age (pooled RR = 1.7, 95% CI: 1.3-2.3), hypoglycemia (pooled RR = 1.6, 95% CI: 1.1-2.3), hyperbilirubinemia (pooled RR = 1.1, 95% CI: 1-1.3), 5 min Apgar <7 (pooled RR = 1.6, 95% CI: 1.1-2.4), admission to the neonatal intensive care unit (pooled RR = 1.5, 95% CI: 1.1-2.1), respiratory distress syndrome (pooled RR = 3.2, 95% CI: 1.8-5.5), and preterm birth (pooled RR = 1.4, 95% CI: 1.1-1.7) was significantly increased in the mild GDM women as compared with the non-GDM population. However, the adverse events of small for gestational age and neonatal death were not significantly different between the groups. Analysis of composite maternal and neonatal outcomes revealed that the risk of those adverse outcomes in the women with mild GDM in all classifications were significantly higher than the non-GDM population. Also, the meta-regression showed that the magnitude of those increased risks in both composite maternal and neonatal outcomes was similar. Conclusion: The risks of sever adverse neonatal outcomes including small for gestational age and neonatal mortality are not increased with mild GDM. However, the increased risks of most adverse maternal and neonatal outcomes are observed. The risks have similar magnitudes for all mild GDM diagnostic classifications.

Continuous Glucose Monitoring in Women with Normal OGTT in Pregnancy

Continuous glucose monitoring (CGM) might be an effective tool to improve glycemic control in gestational diabetes mellitus (GDM). Few data are available about its utilization as a diagnostic tool to find potential alterations of glycemia in subjects with normal oral glucose tolerance test (OGTT). In this preliminary prospective real-life observational study, we aimed to analyze the glycemic pattern in normal and gestational diabetes mellitus (GDM) women by continuous glucose monitoring (CGM) in order to detect potential differences between the two groups and glycemic alterations despite a normal OGTT. After the screening for GDM, subjects were connected to a CGM system for seven consecutive days. The areas under the curve of the first 60 minutes after each meal and 60 minutes before breakfast were analyzed. Women with normal OGTT that during CGM showed impaired glycemic values (more than 95 fasting or more than 140 one hour after meals or more than 120 two hours after meals) performed one week of self-monitoring of blood glucose (SMBG). After OGTT, 53 women considered normal and 46 affected by GDM were included. CGM parameters did not show any differences between the two groups with impaired glycemic excursions found in both groups. After CGM period, 33 women with normal OGTT showed abnormal glycemic patterns. These 33 women then performed one week of SMBG. After evaluation of one week of SMBG, 21 required diet therapy and 12 required insulin treatment and were followed until the delivery. An increase in gestational weight gain was observed in normal women with normal OGTT but this was not significant. No significant data were found regarding neonatal outcomes in the two groups of women. In conclusion, CGM use in pregnancy might help to detect glycemic fluctuations in women with normal OGTT, improving their treatment and outcomes.