  Objective: We hypothesized that prenatal stress (PS) exerts lasting impact on
fetal heart rate (fHR). We sought to validate the presence of such PS signature
in fHR by measuring coupling between maternal HR (mHR) and fHR. Study design:
Prospective observational cohort study in stressed group (SG) mothers with
controls matched for gestational age during screening at third trimester using
Cohen Perceived Stress Scale (PSS) questionnaire with PSS-10 equal or above 19
classified as SG. Women with PSS-10 less than 19 served as control group (CG).
Setting: Klinikum rechts der Isar of the Technical University of Munich.
Population: Singleton 3rd trimester pregnant women. Methods: Transabdominal
fetal electrocardiograms (fECG) were recorded. We deployed a signal processing
algorithm termed bivariate phase-rectified signal averaging (BPRSA) to quantify
coupling between mHR and fHR resulting in a fetal stress index (FSI). Maternal
hair cortisol was measured at birth. Differences were assumed to be significant
for p value less than 0.05. Main Outcome Measures: Differences for FSI between
both groups. Results: We screened 1500 women enrolling 538 of which 16.5 %
showed a PSS-10 score equal or above 19 at 34+0 weeks. Fifty five women
eventually comprised the SG and n=55 served as CG. Median PSS was 22.0 (IQR
21.0-24.0) in the SG and 9.0 (6.0-12.0) in the CG, respectively. Maternal hair
cortisol was higher in SG than CG at 86.6 (48.0-169.2) versus 53.0 (34.4-105.9)
pg/mg. At 36+5 weeks, FSI was significantly higher in fetuses of stressed
mothers when compared to controls [0.43 (0.18-0.85) versus 0.00 (-0.49-0.18)].
Conclusion: Our findings show a persistent effect of PS affecting fetuses in
the last trimester.
