[Severe neonatal encephalopathy, secondary to a prolonged vasovagal episode in a woman 31 weeks pregnant]. / Encefalopatía neonatal grave, secundaria a episodio vasovagal prolongado en una gestante de 31 semanas.

INTRODUCTION: Vasovagal syncope is not frequent during the second half of pregnancy, although the supine hypotension syndrome is common during this period. During these episodes, the marked hypotension may impede uteroplacental blood flow. CASE REPORT: A woman who was 31.5 weeks pregnant lost consciousness for 15 minutes on standing up. 24 hours later, when it was observed that foetal movement had diminished, a cardiotocographic recording was done. This showed a pathological pattern and foetal biophysical profile on echography showed a marked foetal hypotonia and absence of movement. Emergency caesarean section was carried out and a male foetus delivered, weighing 1.810 g, with an Apgar score of 5/6 and requiring intubation and mechanical ventilation for respiratory difficulties and generalized hyptonia with absent reflexes. During the following days he developed generalized hypertonia and died aged 18 days. At necropsy there was severe brain damage, of ischaemic type. Complementary tests on the mother were normal. CONCLUSIONS: Severe prenatal encephalopathy secondary to maternal vasovagal syncope is uncommon, and we have found no report of it in the literature. The prolonged duration of the hypotensive episode, together with prematurity, which implies poor regulation of cerebral blood flow, may have contributed to the severe damage to the central nervous system