Phase-rectified signal averaging as a new method for surveillance of growth restricted fetuses.

Objective: This study aims to compare average acceleration capacity (AAC), a new parameter to assess the dynamic capacity of the fetal autonomous nervous system, and short term variation (STV) in fetuses affected by intrauterine growth restriction (IUGR) and healthy fetuses. Methods: A prospective observational study was performed, including 39 women with IUGR singleton pregnancies (estimated fetal weight 95th percentile) and 43 healthy control pregnancies matched according to gestational age at recording. Ultrasound biometries and Doppler examination were performed for identification of IUGR and control fetuses, with subsequent analysis of fetal heart rate, resulting in STV and AAC. Follow-up for IUGR and control pregnancies was done, with perinatal outcome variables recorded. Results: AAC [IUGR mean value 2.0 bpm (interquartile range = 1.6–2.1), control 2.7 bpm (2.6–3.0)] differentiates better than STV [IUGR 7.4 ms (5.3–8.9), control 10.9 ms (9.2–1...