AIMS To investigate the impact of maternal anticonvulsant use on the ability of cord blood to coagulate.
METHODS Cord blood prothrombin times were measured, over 15 years in a consecutive series of 137 term babies born to women taking phenobarbitone, phenytoin, and/or carbamazepine while pregnant. The response to parenteral vitamin K was measured in 83 neonates.
RESULTS Only 14 of the 105 babies born to the mothers who had therapeutic anticonvulsant blood concentrations at birth had a prolonged prothrombin time (outside the 95% reference range). None had an overt bleeding tendency. The abnormality was corrected within 2 hours by 1 mg of parenteral vitamin K, but rapid intravenous prophylaxis produced complications in three infants.
CONCLUSIONS A policy of giving vitamin K throughout the last third of pregnancy to all women being treated with anticonvulsants, as recently recommended, is not justified by the available evidence. The belief that there is a distinct, early form of neonatal vitamin K deficiency that is different from, and more dangerous than, the classic form of the disease, is not supported by a review of the published evidence.
Few babies born to women taking phenobarbitone, phenytoin and/or carbamazepine have an overt bleeding tendency at birth, although 13% have a prothrombin time that is longer than normal (above the 95% reference range)
A significant number of women seem to be taking subtherapeutic doses of these potentially teratogenic anticonvulsants in an unsupervised (and probably unnecessary) way
Parenteral treatment at delivery suffices to correct the coagulation abnormality within 2 hours (the adequacy of oral treatment remains undetermined)
- anticonvulsant medication in pregnancy
- early vitamin K deficiency bleeding
- prothrombin deficiency
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