Lithium carbonate taken during pregnancy has been associated with neonatal hypotonial and congenital heart disease.2 There is little information on lithium concentrations in human breast milk or in the serum of breast-fed infants. We have studied such a case. Case reportA 36-year-old woman, gravida 1, para 0+1, had been taking lithium carbonate for manic depressive psychosis for seven years when pregnancy was confirmed at eight weeks. The pregnancy was allowed to continue. Initially maintained at 800 mg daily, the dose was reduced twice during pregnancy to maintain therapeutic serum levels (see figure). Her mood was more stable than at any previous time, and she needed no other medication apart from routine haematinics. At 38 weeks she went into spontaneous labour lasting 12 hours and received protective forceps for suspected prematurity. Six hours before delivery she was given pethidine hydrochloride (Pethilorfan) 100 mg and promazine hydrochloride 50 mg. A boy was born weighing 3450 g. He was mildly hypotonic for the first two days. An electrocardiogram showed nothing abnormal, and the blood count and blood sugar level were normal; the lower femoral epiphysis was present.The mother was anxious to breast-feed and this was established within six days. Lithium concentrations in the serum of the mother's pooled breast milk and the baby's urine were all monitored closely. The mother's serum level fell over the time of delivery, and the oral dose was doubled to achieve satisfactory serum levels. The baby's level was similar to the mother's at delivery but fell rapidly to 0 030 mmol/l by the sixth day and then rose slightly once breast-feeding was established. Despite a considerable rise in the mother's serum and breast milk levels there was no appreciable rise in the baby's serum level. He thrived and developed normally. Serial 12-hour collections of his urine on days six to nine inclusive gave lithium concentrations of 0-57, 1-20, 0 45, 0 64, 0 29, 0 30, 0-63, and 0 50 mmol/l. The mother became less anxious to breast-feed and stopped during the tenth week. Tests of thyroid function and bone chemistry were then normal. CommentThe similar serum lithium levels for mother and baby at delivery confirmed that there is free exchange across the placenta.3 The baby's serum level of lithium fell rapidly in the first week of life as reported.3 The mean urinary concentration was 0 57 mmol/l, which was almost 10 times the mean serum level, and this shows that the neonatal kidney is capable of excreting lithium against a concentration gradient. Breast-milk lithium levels were about half maternal serum levels and rose with an increase in the oral dose. Despite the rise in concentration achieved in breast milk, the baby's serum levels remained constantly low-much lower than the level to which he had been exposed during pregnancy. Breast-feeding was discouraged and finally stopped at 10 weeks because of the known inhibition by lithium of cyclic 3'5' adenosine monophosphate4 and the theoretical risk to the developing brain.Since the...

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