Despite lithium has been used for the last 50 years as a maintenance treatment for bipolar disorder during pregnancy, there is limited information about perinatal clinical outcomes from fetal exposure to lithium.

1. 1. To quantify the rate of lithium placental passage

2. 2. To assess any association between plasma concentration of lithium at delivery and perinatal outcome.

Observational and prospective study. Subjects: Women in maintenance treatment with lithium, being attended during pregnancy at the Perinatal Psychiatry Programme of Hospital Clínic (Barcelona, Spain) between 2007 and 2009. Procedure: We assessed sociodemographical data; dose/day of lithium carbonate; other drugs doses; plasmatic concentration of lithium carbonate in maternal blood intrapartum and in the umbilical cord; obstetrical maternal complications; gestational age at delivery; weight at delivery; Apgar scores; congenital malformations; hospital stays, infant serum concetrations of thyroid-stimulating hormone.

Eight mother-child diads. Mean age of the mother (SD): 32.1 (4,7); 100% caucasian and married. Mean dose of maternal lithium (SD): 675mg (237,5mg). Premature rupture of membranes (%):25. Gestational mean age (in weeks) (SD): 39,9 (1). Birth weight (SD) : 3625gr (451,2gr); Mean Apgar1min (SD): 8,38 (1,1); Mean Apgar5min (SD): 9,75 (0,4). Loss of fetal intrapartum wellness (%): 12,5. Days of hospitalization (mean) (SD):9,5(16,6). Lithium plasmatic concentration (mEq/L), mean (SD): maternal 0,45(0,1), umbilical cord 0,33(0,1), lithium ratio uc/m 0,93 (0,3); infant TSH μU/mL mean (SD): 4,9(4,6).

Lithium placental passsage was 0,93 (0,63-1,07). ≤At umbilical cord lithium levels ≤ 0.60 mEq/L, we didn't have any preterm deliveries, low birth weight newborns, nor neonatal complications.