Second-trimester ultrasound, fetal biometrics and gestational diabetes

Gestational diabetes mellitus (GDM) is a frequent metabolic complication of pregnancy. Its incidence is increasing worldwide, with 5–25% of pregnancies diagnosed with GDM depending on screening strategies and diagnostic criteria. GDM may cause obstetric complications and increase the offspring's risk of adult metabolic disease. 

Timely identification of GDM helps regulate maternal glucose levels, which considerably reduces obstetric complications. A recent study by Andersen AS. et al. explains the association between second-trimester ultrasound biometrics and GDM. Their study included 2697 singleton pregnancies attending second-trimester ultrasound scans at 20 + 0 to 20 + 6 weeks gestation and giving birth in the year 2020. They included ultrasound measurements like head circumference (HC), abdominal circumference (AC), femur length (FL), and estimated fetal weight (EFW) by Hadlock's formula. The study, however, excluded women with pregestational diabetes. 

The investigators performed GDM screening on indication using an oral-glucose-tolerance-test (OGTT) including 75 g glucose and considered a 2-hour serum glucose value ≥ 9 mmol/L as diagnostic. 

The investigators diagnosed 6.5 % of the participants with GDM; and found the incidence of GDM in pregnancies with biometrics above the 90th centile as; FL: 10.5 %, HC: 8.8 %, AC: 7.6 %, EFW: 9.3 %. They found that Fetal biometrics above the 90th centile was significantly associated with GDM; ORFL = 2.07; ORHC = 1.89; ORAC = 1.63; OREFW = 1.64; and this association remained significant for HC and FL when adjusted for maternal obesity (Body Mass Index ≥ 27): ORHC(adj)=1.56; ORFL(adj) = 1.57.

Through this study, the investigators concluded that fetal biometrics above the 90th centile at the second-trimester scan increases the risk of GDM. 

In pregnancies, diagnosed with GDM in later stages, fetal growth is already increased at the second-trimester scan. These findings underline the importance of early identification of GDM.

Source: Andersen AS, Rathcke SL, Christensen TT, Sørensen A. The association between second-trimester ultrasound fetal biometrics and gestational diabetes. EJOG. 2022;276:139-143. DOI:https://doi.org/10.1016/j.ejogrb.2022.07.015