FRIDAY, Aug. 26 (HealthDay News) -- The risk of thromboembolism -- a potentially fatal condition in which blood clots block blood flow causing damage to the organs -- is higher during pregnancy, experts warn.

And having a Caesarean section nearly doubles that risk, according to experts at the American College of Obstetricians and Gynecologists. As a result, the group issued a new recommendation that all women having a C-section wear inflatable compression devices on their legs at the time of delivery to prevent clots from forming. In more risky cases, the group advised that women also receive anti-clotting medications (anticoagulants).

"VTE [venous thromboembolism] is a major contributor to maternal mortality in this country. The risk of VTE is increased during pregnancy and the consequences can be severe," Dr. Andra H. James, who helped develop the guidelines, said in a college news release. "It's important for ob-gyns to adopt these recommendations to help reduce maternal deaths."

VTE in pregnancy usually affects the deep veins of the left leg. Most women who develop clots in their lower legs will experience pain or swelling there, the authors noted.

Clots could also travel to the lungs resulting in a pulmonary embolism. Symptoms of this other potentially deadly condition include sudden shortness of breath, chest pain and coughing.

Pregnant women are at greater risk for VTE due to certain physiological changes they experience, including:

• Blood that clots more easily
• Slower blood flow
• Compression of pelvic and other veins
• Decreased mobility

In addition, women who have high blood pressure, a personal history of VTE or excessive clotting, as well as those who are obese or smokers are also at higher risk for the condition.

"Fitting inflatable compression devices on a woman's legs before cesarean delivery is a safe, potentially cost-effective preventive intervention," explained James. "Inflatable compression sleeves should be left in place until a woman is able to walk after delivery or -- in women who had been on blood thinners during pregnancy -- until anticoagulation medication is resumed."

The ob-gyn group pointed out that emergency c-sections are the exception. In these cases, delivery should not be delayed for the placement of compression devices.

Only women at particularly high risk for VTE should be given anti-clotting medication, the experts noted in the news release. This includes those with a history of VTE during pregnancy, a history of excessive clotting, and women at high risk for inherited clotting disorders. All women who've had c-sections, however, should continue to be monitored for VTE following delivery, the group added.

"Because half of VTE-related maternal deaths occur during pregnancy and the rest during the postpartum period, ongoing patient assessment is imperative," James concluded. "While warning signs in some women may be evident early in pregnancy, others will develop symptoms that manifest later in pregnancy or after the baby is born."

The guidelines will be published in a Practice Bulletin in the September issue of Obstetrics & Gynecology.

More information

The U.S. National Heart, Lung, and Blood Institute provides more information on thromboembolism.