As CBS3 meteorologist Kate Bilo discovered the hard way this past weekend, pregnancy and childbirth put even healthy women at increased risk of dangerous blood clots.

Pregnancy can change hormone levels and blood clotting factors, as well as decrease blood flow because of pressure on uterine veins, according to the American Congress of Obstetricians and Gynecologists.

That, in turn, can promote the formation of pulmonary embolisms (lung blood clots like Bilo's) or deep vein thrombosis (leg clots).

The problem is uncommon; fewer than 1 in 10,000 women who have given birth develop dangerous clots. But the risk is highest in the six weeks after delivery. A 2014 study led by Weill Cornell Medical College researchers found the risk during that period was almost 11 times higher than normal. The increased risk declined and disappeared by 18 weeks after delivery.

Bilo, who joined CBS3 as a meteorologist in 2010, gave birth to Solenne Marit Elisabeth late last month — her third child, and first daughter.

While rare, blood clots can cause strokes or heart attacks. On social media, Bilo shared that she initially thought pain in her side and shoulder was the result of straining a muscle while picking up her new baby. She drove herself to the emergency room of an area hospital, where a CT scan revealed the lung clots.

She was put on a blood thinner, which is the standard treatment. "I will have to give myself many injections in the coming months," she wrote.

"Always listen to what your body is telling you," she added. "It would have been so easy for me to write off the pain as muscular or think, 'I'm too busy to go to the ER.' "