Among women with artificial heart valves, pregnancy results in live births in only about two thirds of cases, Lebanese researchers report.

As they explain in the American Journal of Obstetrics and Gynecology, the problem is that people given mechanical heart valves need to take medication continuously to stop blood coagulating around the valves and forming clots.

“Regardless of the treatment modality used for anticoagulation, there is still a substantial risk of thromboembolic complications during pregnancy in such women,” lead researcher Dr. Anwar H. Nassar told Reuters Health.

“Oral anticoagulants (warfarin) are associated with the highest risk of spontaneous abortion and lowest live birth rate compared to heparin or combination of both medications,” Nassar added.

Nassar and his colleagues at the American University of Beirut Medical Center in Lebanon came to these conclusions after reviewing 82 pregnancies in 33 women with mechanical heart valves. Heparin was used during 9 pregnancies, warfarin was used in 30, and both were used during 43 of the pregnancies.

Overall, 66 percent of pregnancies produced live-born babies. There were 12 spontaneous abortions, 7 therapeutic abortions and 9 stillbirths. None involved patients who were given heparin alone.

In addition, one woman on warfarin and four on combination treatment had hemorrhaging after delivery that required transfusion.

There were no maternal deaths, but two patients on heparin and one on warfarin developed valve clots. Surgery was required in one patient, while clot-buster medication dealt with the problem in the other two.

Given these findings, Nassar concluded, “The benefits and the risks of each medication should be carefully weighed before deciding on the best treatment to be used.”

SOURCE: American Journal of Obstetrics and Gynecology, September 2004.