Growing evidence implicates HHV-6, especially HHV-6A, in some cases of female infertility, miscarriage, and other gestational problems affecting both the mother and child. In some women, infertility and miscarriage is successfully treated with heparin, an anticoagulant. In light of this, a new hypothesis paper posits that the use of heparin in these circumstances may be effective in mitigating the detrimental effects of HHV-6 in the uterine environment.
In instances of miscarriage, HHV-6 DNA has been found in fetal tissues, umbilical cord blood, and villous tissue (Revest 2011), and antigen has also been found in villous tissue (Ando 1992). Evidence of an association between the virus and miscarriage has been pronounced in cases of the HHV-6-associated exanthematous disease pityriasis rosea (PR). In a cohort of 38 women who had developed PR during pregnancy, 5 (13%) miscarried, and of the 8 women who developed the illness within the first 15 weeks of gestation, a striking 62% miscarried (Drago 2008). A follow up study revealed similar results for women who developed PR in the first 15 weeks of pregnancy, with 57% of 14 pregnancies ending in miscarriage (Drago 2014). Moreover, in the newest study on the effects of HHV-6 in the female reproductive tract, 43% of women with primary infertility were found to have HHV-6A in their endometrial tissue, while none of the fertile controls were HHV-6 positive (Marci 2016).
Heparin has been found to decrease the infectivity of many viruses, including HSV-1, HSV-1, CMV, KSHV, dengue virus, and ebola virus, especially in endothelial cells, which have been shown to host HHV-6 in the uterus (Marci 2016). The authors note it is also possible that heparin acts to combat an inflammatory environment in the uterus elicited by HHV-6 infection, as heparin can inhibit transcription of IL-1beta, IL-6, and TNF-alpha in mononuclear cells.
Read the full paper and review all of the studies documenting HHV-6 infection in cases of problematic gestational outcomes here: Eliassen 2017.