Assessment and care and major problems of the newborn practice

A woman arrives at a remote clinic in labour, having had no antenatal care and no dating ultrasound. She gives birth to a girl weighing 1980 g who cries at birth, with Apgar scores of 8 and 9. A New Ballard Score performed at 30 minutes estimates the gestational age at 37 weeks. At 90 minutes the baby is quiet, has a weak suck and turns away from the breast. Her temperature is 36.6 degrees, her respiratory rate is 48/min and her perfusion is normal. Which one of the following should be done first?