Transient fetal blood redistribution associated with maternal supine position.
OBJECTIVE
To investigate whether fetal blood circulation is influenced by the maternal supine position.


METHODS
The inclusion criteria were good health, a singleton pregnancy, maternal age between 18 and 40 years, gestational age between 36 and 40 weeks, and an agreement to participate in the study. Each participant (n=20) was initially asked to adopt the left lateral position for 5 min, while fetal Doppler measurements were taken of the fetal middle cerebral artery (MCA), umbilical artery (UA), and umbilical vein (UV). Subsequently, they were asked to change to the supine position for Doppler measurements at 5 and at 10 min.


RESULTS
When a woman remained in the supine position for 5 min, there was a significant reduction in fetal MCA-pulsatility index (PI) (median 1.70 vs. 1.42, P=0.003). This reduction did not persist after 10 min (median 1.70 vs. 1.65 P=1.0). There was no significant difference between the left lateral and the supine position at 5 and at 10 min in terms of UA-PI (0.853 vs. 0.870 vs. 0.858, P=0.850), UV flow (217 vs. 242 vs. 236 mL/min, P=0.263), and normalized UV flow (72.2 vs. 80.8 vs. 78.8 mL/min/kg, P=0.271).


CONCLUSIONS
Changing maternal position from the left lateral to the supine position caused a reduction in resistance in fetal MCA and no changes in UA or UV indices. However, despite the changes in cerebral circulation which occurred at 5 min by shifting position, they did not remain for 10 min. The changes may be related to reduction in maternal oxygen saturation as there was no decrease in UV blood flow.
Department of Obstetrics, Paulista School of Medicine, Federal University of São Paulo, São Paulo.
Karina P
KP
Silva
Department of Obstetrics, Paulista School of Medicine, Federal University of São Paulo, São Paulo.
Tatiana Emy N K
TENK
Hamamoto
Department of Obstetrics, Paulista School of Medicine, Federal University of São Paulo, Rua Napoleão de Barros, 875, Vila Clementino, São Paulo, SP, CEP 04024002.
Roseli M Y
RMY
Nomura
D000328:Adult; D001783:Blood Flow Velocity; D005260:Female; D005333:Fetus / Q000098:blood supply* / Q000000981:diagnostic imaging; D006801:Humans; D007231:Infant, Newborn; D017078:Laser-Doppler Flowmetry; D008297:Male; D020768:Middle Cerebral Artery / Q000000981:diagnostic imaging / Q000502:physiology; D011247:Pregnancy; D016683:Supine Position / Q000502:physiology*; D016216:Ultrasonography, Prenatal; D014469:Umbilical Arteries / Q000000981:diagnostic imaging / Q000502:physiology; D014471:Umbilical Veins / Q000000981:diagnostic imaging / Q000502:physiology; D055815:Young Adult
Doppler velocimetry; fetal circulation; middle cerebral artery; supine position; umbilical artery; umbilical vein