Independent and combined effects of first-trimester elevated fasting blood glucose and high-normal blood pressure on pregnancy outcomes.

AIMS: To evaluate the independent and combined effects of first-trimester elevated fasting blood glucose (EFBG, FBG ≥ 5.1 mmol/L) and high-normal blood pressure (HNBP, SBP: 120-139 mmHg and/or DBP: 80-89 mmHg) on adverse pregnancy outcomes among southern Chinese women with singleton pregnancies.

METHODS

This single-center retrospective cohort study enrolled 9,432 women who registered for antenatal care and delivered at the Department of Obstetrics and Gynecology, Guangxi Zhuang Autonomous Region People's Hospital between January 2018 and December 2023. Participants were stratified into four groups according to first-trimester FBG and BP measurements: control group (G1, n = 7,192), isolated EFBG group (G2, n = 784), isolated HNBP group (G3, n = 1,212), and co-exposure group (G4, n = 244). Multivariable logistic regressionwas used to estimate adjusted odds ratios (aOR) for adverse pregnancy outcomes. Additive interactions between EFBG and HNBP were assessed using relative excess risk due to interaction (RERI), attributable proportion (AP), and the synergy index (S), estimated from modified Poisson regression models with bootstrap resampling.

RESULTS

Compared with the G1, the G3 had a significantly higher risk of hypertensive disorders of pregnancy (HDP) (aOR = 4.36, 95%CI: 3.51-5.40), and the G2 had a significantly higher risk of gestational diabetes mellitus (GDM) (aOR = 2.40, 95%CI: 2.06-2.81).. The G4 exhibited the highest risk of GDM (aOR = 4.29, 95%CI: 3.24-5.68). However, the additive interaction analysis did not reveal a statistically significant synergistic effect between EFBG and HNBP for GDM (RERI = 0.10, 95% CI: -0.15 to 0.35). The G3 was also associated with increased risk of preterm birth (aOR = 1.92, 95%CI: 1.45-2.55), low birth weight (LBW) (aOR = 2.15, 95%CI: 1.65-2.81), and small for gestational age (SGA) (aOR = 1.28, 95%CI: 1.04-1.57), whereas the G2 was associated with increased risk of large for gestational age (LGA) (aOR = 1.33, 95%CI: 1.06-1.66) and macrosomia (aOR = 1.66, 95%CI: 1.17-2.37).

CONCLUSION

First-trimester EFBG and HNBP are independent predictors of distinct adverse pregnancy outcomes. EFBG is associated with metabolic complications (GDM, macrosomia, LGA), while HNBP is associated with vascular complications (HDP, LBW, SGA), isolated diastolic and combined HNBP conferring particularly high HDP risk. Although the co-exposure group had the highest absolute risk of GDM, no significant additive or multiplicative interaction was observed. These findings support combined glucose-blood pressure screening in early pregnancy for risk stratification..