Women who have just given birth should wait at least three weeks before they start using birth control pills because of the risk of serious, potentially fatal blood clots, public health officials announced recently. Women who deliver by Caesarean section or have other risk factors for blood clots like obesity or a history of previous blood clots should wait at least six weeks before using these medications, they said.

The new recommendations, by the Centers for Disease Control and Prevention, are similar to recommendations made in 2010 by the World Health Organization.

Women are far more likely to develop a blood clot in the weeks after delivery than nonpregnant women of reproductive age who have not just had a baby, several studies have shown. The risk declines rapidly after 21 days but does not return to normal until 42 days after delivery.

Pills that include both estrogen and progestin also increase the risk of blood clots in the deep veins (venous thromboembolism). Women who are breast-feeding may want to avoid hormonal contraceptives because they can interfere with lactation, the CDC said. — New York Times News Service

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