Researchers propose guidelines for lithium use in pregnancy

Guidelines for the administration of lithium to women with bipolar disorder during late pregnancy are proposed by the authors of a recent US study.The safety of lithium use during late pregnancy has not been systematically investigated. However, the morbidity and risk of perinatal relapse associated with withholding treatment mean that prolonged discontinuation of the drug is seldom a viable option.The researchers aimed to quantify the rate of lithium placental passage, to investigate whether infant lithium concentration at birth and the incidence of perinatal events are linked, and to determine whether lithium concentrations can be reduced by briefly suspending therapy immediately before delivery.The study included ten women with bipolar disorder referred to a mental health program that routinely instructs patients to discontinue lithium therapy one to two days before a scheduled delivery or at the onset of labour if unscheduled.Maternal and umbilical cord blood samples were obtained from all subjects during gestation and at delivery. Obstetrical outcomes were also recorded.Lithium concentrations were determined for ten umbilical cord samples and nine maternal samples. In addition, the researchers identified in the literature a further 18 foetal-maternal pairs exposed to lithium at delivery and for whom lithium concentrations were reported.The mean infant-mother lithium ratio for the 27 pairs was found to be 1.05, indicating complete placental passage.In addition, the mean infant-mother lithium ratio was almost identical between infants with a low or high lithium exposure (>0.64meq/litre), indicating that degree of placental passage does not vary with maternal plasma lithium concentration within the clinical range of concentrations encountered.With the exception of gestational diabetes, all complications occurred more frequently in the high lithium exposure group, particularly central nervous system and neuromuscular complications. In addition, infant hospital stays were significantly longer and 1-minute Apgar scores significantly lower in this group.Although subjects' lithium therapy was interrupted briefly prior to delivery, resulting in reduced lithium concentrations, only one of the 10 women in the mental health program was symptomatic in the perinatal period.In light of their findings the researchers propose guidelines for the administration of lithium during late pregnancy comprising eight points.They conclude: "When lithium is used during late pregnancy, infant and maternal well-being can be maximised by maintaining maternal concentrations at the minimal effective level, suspending lithium therapy 24-48 hours before delivery to reduce neonatal concentrations further, and avoiding inadvertent or iatrogenic lithium toxicity during gestation."Reference...