Hematologists Perspective

Doctors (both OBs and Hematologists) seem to disagree at times about how to treat Factor V Leiden in pregnancy. I recently ran across these two Q & As from the Baylor College of Medicine "ask the expert" site. I would urge anyone who's doctors are not willing to treat their clotting issue in order to prevent recurrent pregnancy loss to seek out a different doctor. Here's what the Hematologist at Baylor says: Subject: Factor V Leiden Q: I have had two miscarriages this year (6 and 10 weeks). My ob/gyn ordered a lot of tests and a chromosomal analysis after my second miscarriage. My chromosomal analysis came back completely normal but she said that I have factor V Leiden Mutation (hetero). I was told that this may have caused both of my miscarriages. My doctor said that I needed to see a hematologist who would determine whether I needed to take children's aspirin or a blood thinner the next time I get pregnant. I was referred to a hematologist who emphatically told me that FVL did not cause my miscarriages. The hematologist told me that FVL would not cause me any problems until the very end of my pregnancy, if at all. At this point, I was real upset because I didn't know which doctor was right. To make things worse, I later read the literature that the hematologist gave me and it stated that "All patients with a history of unexplained fetal demise would probably be treated". Another handout she gave me stated "If you are factor V Leiden positive and you have never suffered from a clot, you probably do not need any therapy on a routine basis. Protective anticoagulant therapy may be needed is situations where your risk for developing a clots is increased, such as during pregnancy and the post partum period". I would very much appreciate any insight you can offer. A: Most studies confirm an association between conditions such as like Factor V Leiden and both early and late miscarriages. Given your history, we would recommend injections of the blood thinner Lovenox 40 mg daily throughout pregnancy (and for 2-3 months post-delivery). Dr. Lawrence Rice or Dr. Kelty Baker would be happy to see you for a consultation, if you wish. The appointment number for both Dr. Rice and Dr. Baker is 713-394-3800. References: Kupferminc, NEJM 340:9-13,1999 or Walker, J Clin Pathol 53:573-580, 2000. Q: I recently tested positive for Factor V Leiden, heterozygous. I am EXTREMELY curious about the relationship b/w FVL and late term pregnancy loss. Any information you could provide would be greatly appreciated. I have done a tremendous amt of research on this and all the research says there is a correlation, however, I have heard mixed theories. I would also like to know your advice on treatment for a subsequent pregnancy if one had suffered a late term loss (lost 10 lb. baby girl at 38 weeks gestation.) I am finding there is also a very gray area on this topic. I have never suffered any medical problems. I am active and healthy. A: Most studies confirm an association between thrombophilia (increased incidence of blood clotting such as seen with Factor V Leiden) and both early and late miscarriages. As mentioned above, our expert would recommend treatment with the blood thinner Lovenox 40 mg by injection daily throughout pregnancy and for 2-3 months after delivery.

Necessity of treatment for recurrent loss w/ FVL

It's almost impossible to find large, randomized studies on factor v leiden and pregnancy. The stakes are high and it is difficult for researchers to recruit. So, even though these studies are small, for those of us who are looking for answers, they are very valuable.

2001 Oxford Journal Human Reproduction showed that the live birth rate for women with FVL AND a history of losses (3 losses or a 2nd or 3rd trimester loss) was even lower than the 49% birth rate for women with similar histories but who had normal Factor V genotype. This study observed pregnancies with no treatment beyond standard prenatal care.

Luckily, treating a clotting disorder can significantly improve the outcomes for women with late or recurrent losses. 2011 Habenox study showed that women with recurrent loss and diagnosed thromobophilia (FVL, Prothrombin, Protein S or C deficiencies, etc.) had approximately 70% live birth rate when treated with 40 mg enoxaparin/lovenox and/or 80mg aspirin daily. Most (90%) of the losses that did occur were 1st trimester miscarriages.

Unfortunately, not all doctors will treat recurrent loss with blood thinners. A study cited by an ACOG practice bulletin of "low risk" women (i.e. no history of recurrent loss) showed that the 134 women with FVL had comparable live birth rates to other low-risk women. For this reason, ACOG does not recommend treating women with FVL unless there is a history of clots. FVL can be very sporadic in it's effects. I had 3 full term births before my diagnosis. But, if it has caused late or multiple losses for a particular mother, the odds are stacked against her for future pregnancies without treating the FVL. (Note: Studies showing the benefits of treatment for recurrent loss are discounted by the ACOG bulletin. Thankfully, many good OBs & Maternal-Fetal medicine specialists DO treat these high-risk populations instead of sitting on their haunches waiting for a large, randomized, double-blind study verifying what more moderately sized studies have already shown- that treating the clotting disorder reduces the risk of further losses.) If you've had multiple or late losses and your doctor cites this practice bulletin as the reason you shouldn't treat your genetic thrombophilia, please find a new doctor.