CIRCADIAN FUNCTION ACROSS PREGNANCY AND EARLY POSTPARTUM BY CHRONOTYPE PROFILE

The transition from late pregnancy (P) to early postpartum (PP) implies changes in sleep–wake timing and light exposure that may reduce overall circadian function. The influence of individual chronotype on this transition has not been fully explored probably because its measurement relies on proxies that may disagree. We therefore integrated subjective and objective chronotype measures to derive chronotype profiles and to examine whether changes in Circadian Function Index (CFI) and daytime light exposure differ by profile. Uruguayan pregnant participants (n=46) completed MEQ/MCTQ questionnaires and wore wrist actimeters with light sensors during P (30 weeks) and at one-month PP. Timing features (MSFsc, L5c timing, mid-sleep timing, acrophase) were standardized and submitted to unsupervised k-means clustering. Changes P-PP within profile were tested with paired-Wilcoxon tests and Benjamini–Hochberg correction. Chronotype proxies frequently disagreed (30/46, 65.2%). Clustering supported a two-profile solution: Early (EP) vs Late (LP), with LP exhibiting consistently later timing across features ([20-57] min). Consistently, MEQ score was marginally higher in EP than in LP (E: 55, L:48, p=0.06). Overall, PP was characterized by lower CFI (p=0.04) and reduced daytime light exposure (p=0.01). CFI decreased from P to PP in EP (P:0.623; PP:0.553; p= 0.013); while LP showed a trend in the same direction (p = 0.061). Daytime light exposure also showed a marginal decrease at PP in both EP and LP (p= 0.06). Our results provide a reproducible framework to stratify perinatal circadian function and suggest that chronotype may influence the vulnerability of circadian well-being across the perinatal transition.