Having recently reviewed the case notes of babies readmitted to hospital in the first 10 days of life (over a one year period), we firmly agree with the views expressed by Laing and Wong.¹ The incidence of documented hypernatraemic dehydration secondary to the failure of lactation in Bristol is 1.7 per 1000 live births much higher than that described by Oddie et al in the Northern Region (2.5 per 10 000 live births).² In addition only 50% of infants readmitted with weight loss of <10% had a plasma sodium concentration measured. The true incidence of hypernatraemic dehydration secondary to lactation problems in Bristol could thus be as high 3.4 per 1000 live births. Our estimate could be an underestimate. Firstly, our study looked only at infants readmitted within 10 days (Oddie et al looked at infants readmitted up to 1 month of age) and secondly, due to failure to recognise of this condition.

Laing and Wong proposed weighing all infants when the Guthrie blood samples are taken, to identify those infants at risk of dehydration.¹ We believe that this is too late as in many areas this occurs on days seven or on day 10 with handover of care to the health visitor. We have already described a series of babies with hypernatraemic dehydration where all presented to hospital before day seven.³

The case has been made correctly that newborn hypernatraemia is due to unsuccessful feeding.^1,4 While we agree that careful examination and observation of the infant while feeding and so forth may identify these babies, we would dispute that this is currently universally possible. Due to midwifery shortages, postnatal wards are short staffed and community midwives are fully stretched, so many women are discharged within a few hours of delivering. If a midwifery home visit does not coincide with a feed, the mother’s assessment of feeding is assumed to be correct (as indeed it usually is). Weighing the baby will reassure most mothers that their baby is following the normal pattern of loss followed by gain. Identification of excessive weight loss should prompt the health professional to examine the baby for evidence of illness and carefully observe breast feeding technique. These mother-baby dyads could then be given additional support and advice in the community and thus successfully establish feeding. In our experience once the baby has become ill and required readmission to hospital the mother is reluctant to continue to attempt to breastfeed.

There continues to be confusion regarding the best way to manage this problem.^1,5 It should be remembered that these babies have normal guts and are suffering from starvation. If the infant is not shocked, rehydration can occur safely using enteral fluids: expressed breast milk or a breast milk substitute. Serum sodium should be measured six hourly initially and the volume of milk altered to ensure a slow return to normality.

We believe that we need to foster a greater awareness of this problem and weigh the babies at risk around day five if we are to prevent tragedies resulting from a common condition affecting otherwise well babies.