Maternal prenatal perceived stress shapes maternal–fetal cardiac coupling: insights from nonlinear recurrence analysis

Abstract Maternal prenatal perceived stress (PPS) may alter maternal–fetal cardiac regulation, but effects on nonlinear dynamics and dyadic coupling remain unclear. We analyzed baseline (~ 5-min) maternal and fetal R–R (mRR, fRR) series from 57 third-trimester dyads stratified by PPS with a validated scale (LOW n = 6, MODERATE n = 34, HIGH n = 17). Linear heart rate variability (HRV) and recurrence quantification analysis (RQA) were applied to mRR and fRR, and cross-recurrence quantification analysis (CRQA)—including diagonal, lag-resolved analysis—was used to assess maternal–fetal cardiac coupling (MFCC). In mRR, the MODERATE group showed reduced linear HRV compared with LOW and HIGH, while HIGH showed a shift toward more organized/less complex dynamics, with higher RQA metrics (Lmean mRR , ENTR mRR , LAM mRR ) than LOW (all p < 0.05). In fRR, linear HRV showed no differences across groups, but RQA distinguished HIGH from MODERATE and LOW, with HIGH exhibiting higher DET fRR and LAM fRR , indicating more regular fetal cardiac dynamics under increased maternal stress. At the dyadic level, global CRQA indices were broadly comparable across PPS levels. However, the diagonal analysis of cross-recurrence plots revealed a delay-structured, directionally biased interaction: the maternal → fetal direction was most sustained in HIGH, present but fragmented in LOW, and least organized in MODERATE. These findings suggest that PPS was associated with more recurrent maternal dynamics, stress-related reorganization of fetal recurrence patterns, and subtle, delay-specific changes in MFCC not visible in linear HRV alone—consistent with a loss of nonlinear complexity features—and supporting RQA/CRQA as complementary tools for perinatal stress phenotyping.