P05.17: Arterial and venous cerebral circulatory responses to acute hypoxemia in growth restricted human fetuses with brain‐sparing blood flow

were beneath the 3rd centile. The patient was counselled regarding the poor prognosis for this fetus. The patient elected to continue with the pregnancy. Repeated scans at 20, 21, 24, 26, and 27 weeks showed persistent oligohydramnios with the mean pool depth decreasing from 17 mm to 15 mm. From 20 weeks umbilical artery Doppler showed absent end-diastolic flow, although this never reversed. At 28 + 1 weeks’ gestation, the patient presented with antepartum haemorrhage, and uterine contractions. Ultrasound confirmed fetal viability. Labour progressed spontaneously, a female infant with a birthweight of 355 g was delivered with APGAR scores of 3 at 1 minute, and 8 at 5 minutes. The infants abdominal circumference was 24.5 cm and head circumference was 21.5 cm, both beneath the 3rd centile for gestation age and gender. The placenta was noted to be extremely small and gritty. The infant had an uneventful neonatal period with no evidence of respiratory distress, necrotising enterocolitis, intracranial damage or infection. Chromosomal analysis was normal. She was discharged at 95 days of age. Despite severe placental insufficiency as diagnosed by Doppler ultrasound this fetus survived to extra-uterine life. It is hypothesised that the second wave of trophoblastic invasion failed, leading to a period of chronic physiological stress in the fetus allowing it to survive.