To avoid potentially deadly blood clots -- public health officials say women should wait at least 3 weeks after giving birth to go back on birth control pills.

That recommendation is from the Centers for Disease Control -- where experts say the risk for blood clots is elevated for about 21 days after having a baby -- then usually decreases.

But women who had a c-section or have other risk factors -- like obesity or a history of blood clots -- may need to wait at least 6 weeks before returning to the pill.

The estrogen and progestin in birth control pills are associated with a slightly increased risk for clots.