Signs of fetal brain sparing are not related to umbilical cord blood gases at birth

Abstract

Background Fetal chronic hypoxia leads to centralization of circulation in order to spare the vital organs brain, adrenals and the heart. This can be documented by Doppler ultrasound. Increased blood velocity in the fetal middle cerebral artery (MCA) is an acknowledged sign of centralization of circulation in chronic hypoxia, and is called brain sparing. Aim Our aim was to assess the relationship between signs of brain sparing in the MCA and umbilical cord blood gases at birth. Study design A prospective study. Subjects Singleton 57 high-risk pregnancies (outcome was compared with 21 normal pregnancies). Methods MCA Doppler was performed within 24 h of elective caesarean section in high-risk pregnancies. Umbilical cord blood gases were analysed at birth. Main outcome measures Cord blood gases were related to signs of centralization of fetal circulation in the MCA. Results No correlation between signs of brain sparing in the MCA and cord blood gases. Apgar score at 5′ < 7 was seen in three newborns, but only one of these had antenatal signs of brain sparing. Newborns with antenatal brain sparing were admitted more often ( p < 0.04) and had a longer duration of stay in NICU ( p < 0.03) compared to newborns without brain sparing. Conclusion Decreased pulsatility index in MCA is an acknowledged sign of fetal centralization of circulation during chronic hypoxia. However, signs of brain sparing are not related to cord blood gases at birth, which might suggest that redistribution of fetal circulation can maintain normal blood gases for a long time during chronic hypoxia.