Pregnancy Complications in Northern China Show Distinct Risk Profiles Across Seven Years of Hospital Data

A sweeping analysis of more than 264,000 singleton deliveries across 31 hospitals in Hebei Province, China, has mapped how two of the most common pregnancy complications—hypertensive disorders of pregnancy (HDP) and gestational diabetes mellitus (GDM)—appear in hospital records over seven years, and how each shapes the risks that mothers and babies face. The retrospective multicenter cohort study, drawing on the Hebei Obstetric Critical Illness Monitoring System from 2017 to 2023, found that these conditions carry distinct but overlapping outcome profiles, with HDP showing particularly strong associations with placental and fetal-growth complications while GDM was linked chiefly to fetal overgrowth and premature rupture of membranes. The findings, published in Frontiers in Public Health, also revealed a striking discontinuity in recorded GDM prevalence after 2021 that the authors caution cannot be confidently interpreted as a genuine population-level decline.

Among the 264,278 eligible deliveries analyzed, 11,708 (4.43%) were classified as HDP alone, 18,600 (7.04%) as GDM alone, 2,138 (0.81%) as coexisting HDP and GDM, and 231,832 (87.72%) as unaffected by either recorded condition. The study included live births and 135 stillbirths, covering deliveries at 28 or more gestational weeks with complete core maternal and perinatal outcome information. GDM was diagnosed using a 75-gram oral glucose tolerance test performed at 24 to 28 gestational weeks, with diagnostic thresholds of fasting venous plasma glucose at or above 5.1 mmol/L, 1-hour glucose at or above 10.0 mmol/L, or 2-hour glucose at or above 8.5 mmol/L. Random plasma glucose alone was not used to assign a GDM diagnosis, and pregestational or overt diabetes first recognized in pregnancy were excluded from the four-group comparison.

The recorded temporal patterns told a complex story. HDP-alone prevalence rose steadily from 3.42% in 2017 to 7.60% in 2023. GDM-alone prevalence climbed from 4.77% in 2017 to a peak of 13.21% in 2021, then fell abruptly to 1.76% in 2022 and 1.96% in 2023. Coexisting HDP-GDM followed a similar trajectory, rising to 1.39% in 2021 before dropping to 0.26% in 2022 and 0.23% in 2023. The decline between 2021 and 2022 was substantially larger than any preceding annual change and occurred while the total number of deliveries captured by the registry also decreased—from 64,629 in 2017 to 22,419 in 2023. The number of participating hospitals fluctuated as well, from 28 in 2017 to a high of 31 in 2019, then down to 24 in 2021, 16 in 2022, and 14 in 2023.

The authors emphasize that this post-2021 discontinuity cannot be confidently attributed to rapid biological change at the population level. In a sensitivity analysis restricted to 10 hospitals that participated throughout the study period, recorded GDM-alone prevalence was 4.90, 6.87, 9.08, 10.36, 12.58, 2.02, and 2.10% from 2017 through 2023, with corresponding center-standardized estimates from a binomial mixed model with hospital-specific random intercepts of 4.92, 6.84, 9.01, 10.29, 12.52, 2.10, and 2.18%. The discontinuity persisted in these analyses, although the 2022 and 2023 values were higher than the all-center proportions. However, annual oral glucose tolerance test eligibility and completion denominators were unavailable, and a comprehensive center-year audit of pandemic-related service changes was not conducted. Without such data, the recorded fall cannot be distinguished from changes in antenatal attendance, screening completion, laboratory practice, diagnostic coding, or case reporting within hospitals. The authors therefore describe these figures as registry-recorded patterns rather than a confirmed public-health improvement.

Turning to outcomes, the study found that HDP alone showed the strongest adjusted associations with placental abruption, preterm delivery, small-for-gestational-age birth, and neonatal asphyxia. After multivariable logistic regression adjusting for maternal age, marital status, education, hospital level, gravidity, parity, prenatal examination frequency, and previous cesarean section, HDP alone was associated with cesarean delivery (odds ratio 3.28, 95% confidence interval 3.12–3.45), placental abruption (OR 37.44, 95% CI 28.13–49.84), postpartum hemorrhage (OR 1.72, 95% CI 1.51–1.97), anemia (OR 1.64, 95% CI 1.57–1.71), and hypothyroidism (OR 1.13, 95% CI 1.02–1.25). HDP alone was also associated with late preterm delivery at 34 to 36 plus 6 weeks (OR 9.99, 95% CI 9.19–10.86), early preterm delivery at 28 to 33 plus 6 weeks (OR 4.79, 95% CI 4.50–5.09), small-for-gestational-age birth (OR 10.27, 95% CI 9.59–10.99), neonatal asphyxia (OR 3.74, 95% CI 3.22–4.34), and stillbirth (OR 3.12, 95% CI 1.73–5.64).

GDM alone carried a different risk signature. It was associated with macrosomia, defined as birth weight above 4,000 grams (OR 1.41, 95% CI 1.34–1.46), and with premature rupture of membranes (OR 1.38, 95% CI 1.30–1.47), but not with small-for-gestational-age birth (OR 0.93, 95% CI 0.81–1.06) or neonatal asphyxia (OR 1.05, 95% CI 0.85–1.30) after adjustment. GDM alone was also associated with cesarean delivery (OR 1.13, 95% CI 1.08–1.17), late preterm delivery (OR 1.40, 95% CI 1.30–1.51), early preterm delivery (OR 1.54, 95% CI 1.36–1.75), postpartum hemorrhage (OR 1.70, 95% CI 1.52–1.90), anemia (OR 1.49, 95% CI 1.44–1.54), and hypothyroidism (OR 1.31, 95% CI 1.21–1.41). The stillbirth estimate for GDM alone was OR 1.95 (95% CI 1.06–3.59), though the authors note that the confidence interval for this association included 1 after hospital-specific random-intercept adjustment.

The coexisting HDP-GDM group showed a mixed profile rather than uniformly higher point estimates than HDP alone. It was associated with cesarean delivery (OR 2.36, 95% CI 2.10–2.64), placental abruption (OR 18.90, 95% CI 10.61–33.65), postpartum hemorrhage (OR 2.32, 95% CI 1.78–3.03), anemia (OR 1.81, 95% CI 1.66–1.98), hypothyroidism (OR 1.83, 95% CI 1.52–2.19), late preterm delivery (OR 3.99, 95% CI 3.48–4.57), early preterm delivery (OR 5.54, 95% CI 4.51–6.81), macrosomia (OR 1.48, 95% CI 1.29–1.69), small-for-gestational-age birth (OR 5.87, 95% CI 4.97–6.94), and neonatal asphyxia (OR 2.98, 95% CI 2.10–4.24). The stillbirth estimate for this group was not statistically significant (OR 1.35, 95% CI 0.19–9.74) and was based on a single event, providing little information about true stillbirth risk. Similarly, puerperal infection estimates were highly imprecise because only one and two events occurred in the coexisting group for stillbirth and puerperal infection, respectively. The authors stress that because each exposure group was compared separately with the unaffected reference group, the differences between their odds ratios are not formal head-to-head comparisons and should not be interpreted as evidence that coexistence is protective.

Maternal demographic characteristics also differed across groups. Pregnancies complicated by HDP, GDM, or both had older maternal age distributions than unaffected pregnancies, with mean ages of 30.31, 30.75, and 30.89 years respectively, compared with 29.47 years in the unaffected group. The coexisting HDP-GDM group had the highest proportion of women aged 40 or older at 5.1%, compared with 4.0% for HDP alone, 3.0% for GDM alone, and 1.9% for unaffected pregnancies. Cesarean delivery rates were markedly elevated across complication groups: 75.73% for HDP alone, 59.35% for GDM alone, and 73.85% for coexisting disease, against 51.79% in unaffected pregnancies. Term delivery rates were 77.14% for HDP alone, 93.20% for GDM alone, and 81.52% for the combined group, compared with 95.37% among unaffected pregnancies.

The authors conducted exploratory E-value calculations to summarize approximate sensitivity to unmeasured confounding for positive associations whose confidence intervals excluded 1. For coexisting HDP-GDM, the approximate E-values for the point estimate and lower confidence limit were 37.03 and 20.63 for placental abruption, 10.05 and 8.16 for early preterm delivery, 10.46 and 8.87 for small-for-gestational-age birth, 5.35 and 3.59 for neonatal asphyxia, and 2.19 and 1.83 for macrosomia. These sensitivity summaries varied substantially by outcome and do not demonstrate that confounding, selection, or ascertainment bias is absent. The median hospital intraclass correlation coefficient was 0.047, with a range of 0.018 to 0.109. Hospital-random-intercept outcome estimates retained the direction of the original associations, though the HDP-alone/hypothyroidism and GDM-alone/stillbirth intervals included 1 after hospital adjustment.

Several limitations frame the interpretation of these findings. The retrospective design and incomplete measurement of metabolic, behavioral, treatment, and family-history covariates—including pre-pregnancy body mass index, gestational weight gain, smoking, alcohol use, assisted reproductive technology, medication exposure, and dietary factors—preclude causal inference. HDP was analyzed as a composite exposure, and the available reporting does not support reliable subtype-specific estimates. The exclusion of recorded pregestational or overt diabetes does not guarantee the absence of unrecognized pre-existing dysglycemia. The authors caution that the study odds ratios should not be converted into unvalidated visit-frequency or testing thresholds, and instead support guideline-concordant integrated care in which blood pressure and glycemic control are reviewed together, fetal growth is assessed serially according to clinical risk, and women with severe hypertension or abnormal growth findings are referred promptly to tertiary centers. Postpartum follow-up remains important, as women with prior HDP have an increased long-term risk of chronic hypertension and women with GDM have an increased risk of type 2 diabetes, though the current registry did not evaluate long-term outcomes. The findings should be interpreted as registry-based associations rather than causal effects or definitive population trends, and the authors call for prospective studies with standardized diagnostic procedures and comprehensive metabolic covariates.

Subject of Research: Temporal patterns and pregnancy outcomes of hypertensive disorders of pregnancy and gestational diabetes in Hebei Province, China

Article Title: Temporal patterns and adverse pregnancy outcomes of hypertensive disorders of pregnancy and gestational diabetes mellitus in Hebei Province, China, 2017–2023: a multicenter retrospective cohort study

Article References: Liu, L., Liu, S., Du, L., Yin, X., & Huo, Y. (2026). Temporal patterns and adverse pregnancy outcomes of hypertensive disorders of pregnancy and gestational diabetes mellitus in Hebei Province, China, 2017–2023: a multicenter retrospective cohort study. Frontiers in Public Health, 14, Article 1885150. https://doi.org/10.3389/fpubh.2026.1885150

Image Credits: AI Generated

DOI: 10.3389/fpubh.2026.1885150

Keywords: hypertensive disorders of pregnancy, gestational diabetes mellitus, adverse pregnancy outcomes, preterm birth, placental abruption, macrosomia, small for gestational age, retrospective cohort study, China, Hebei Province, maternal health, neonatal outcomes