Patterns of Combined Prenatal Supplement Use and Associations with Birth Outcomes and Early Infant Growth: A Multicenter Prospective Mother–Infant Cohort Study in China

Background: Women often use several prenatal supplements together, yet most studies evaluate products one at a time. Objective: To identify longitudinal patterns of combined prenatal supplement use and assess their associations with cesarean delivery, birth size, jaundice, and early infant growth. Methods: This multicenter cohort included 1758 mother–infant pairs from 16 provinces in China. Supplement use was reported once in the baseline questionnaire: on or before delivery for 876 women (median gestational age 38.57 weeks) and after delivery for 809. For each of seven supplements, use frequency was reported once, and participants indicated the pregnancy periods during which the supplement was used. One frequency was assigned to every period endorsed from preconception through the third trimester, giving 28 indicators for latent class analysis. Associations were estimated in exploratory multivariable models, with Benjamini–Hochberg correction within outcome families. Results: Six patterns were identified. They differ in product combination, endorsed periods, and one recorded frequency per product, and are not ordered by dose (C6 (low use), 25.7%; C4 (all-supplement high-frequency), 7.0%). Membership differed by region, parity, and pregnancy complications. Compared with C6, mid-late high-frequency core use (C5) was nominally associated with lower odds of cesarean delivery (adjusted OR 0.72, 95% CI 0.53–0.99). Persistent multi-supplement high-frequency use (C3) and all-supplement high-frequency use (C4) were nominally associated with higher odds of physiological jaundice recorded at the 40–60-day follow-up (1.65, 1.00–2.70 and 1.86, 1.04–3.27), and C4 with shorter birth length (adjusted β −0.46 cm, 95% CI −0.81 to −0.10). These associations did not remain significant after within-family correction. Macrosomia, infant eczema, and gains in length and weight showed no association. Greater head-circumference gain in mid-late moderate core use (C1) remained significant after correction (adjusted β 0.87 cm, 95% CI 0.34–1.40; q = 0.019) among 513 infants in the adjusted analysis. Conclusions: Supplement use clustered into six patterns of timing and reported frequency. The associations are observational and do not show that changing a supplement regimen would change these endpoints.