Mid-trimester sum-estimated fetal weight and gestational diabetes risk in twin pregnancies

Gestational diabetes mellitus (GDM) is more prevalent in twin pregnancies, yet screening strategies remain largely based on singleton data. In the present study, we aimed to evaluate whether the mid-trimester sum of estimated fetal weights (sum-EFW) at the anatomy scan is associated with subsequent GDM in twin pregnancies.

We conducted a retrospective cohort study of twin pregnancies undergoing routine mid-trimester ultrasound (2010-2025) at a tertiary center. Sum-EFW was calculated as the combined estimated fetal weight of both fetuses. The primary outcome was GDM. Receiver operating characteristic (ROC) analysis assessed discriminative performance and multivariable logistic regression identified independent predictors.

Among 728 women, 70 (9.6%) developed GDM. Sum-EFW was higher in GDM pregnancies (1177 ± 187.9 vs. 1103 ± 178.8 g; P = 0.001). ROC analysis demonstrated modest discriminative ability (area under the curve [AUC] 0.62; 95% confidence interval [CI]: 0.55-0.69; P = 0.001). After adjustment for gestational age, discrimination was similar (AUC 0.586; 95% CI: 0.518-0.655; P = 0.013), with sensitivity 67.1%, specificity 47.6%, positive predictive value (PPV) 12.1%, and negative predictive value (NPV) 93.1% at the optimal threshold. A cutoff of 1130 g identified a higher-risk subgroup (14.3% vs. 6.3%; P = 0.001). In multivariable analysis, maternal age ≥ 30 years (adjusted odds ratio [aOR] 2.45; 95% CI: 1.10-5.45), body mass index (BMI) ≥30 (aOR 5.48; 95% CI: 2.33-12.85), and sum-EFW ≥1130 g (aOR 3.21; 95% CI: 1.41-7.34) were independently associated with GDM.

In twin pregnancies, a higher mid-trimester sum-EFW is independently associated with subsequent GDM. These findings suggest that combined fetal growth may reflect early metabolic alterations in twin gestations. Discrimination remains modest, limiting use as a screening or risk-stratification tool.