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Abstract
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.
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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)
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A significant number of women seem to be taking subtherapeutic doses of these potentially teratogenic anticonvulsants in an unsupervised (and probably unnecessary) way
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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