Does low molecular weight heparin influence the triple test result in pregnant women with thrombophilia?

Background: The triple test serum markers for Down's syndrome screening may be altered because of various conditions other than chromosomal trisomies. Objectives: To assess the profile of mid-trimester triple test serum markers in a cohort of women treated with low molecular weight heparin (LMWH) for thrombophilia since the first trimester. Methods: Women with inherited or acquired thrombophilia treated with LMWH prior to 12 weeks gestation were followed between October 2006 and September 2009 at our obstetric outpatient clinic. The second-trimester screening test for Down syndrome was calculated from the combination of triple serum markers and maternal age, and expressed as a multiple of the gestation-specific normal median (MoM). Reference MoM values were calculated from the local population. Data on pregnancy outcome were obtained from patient records. Results: The median human chorionic gonadotropin (hCG) level of women with inherited thrombophilia was 0.87 MoM, compared to 0.99 MoM in controls (P = 0.038) and compared to 1.355 MoM in women with acquired thrombophilia (P =0.034). In contrast, alpha-fetoprotein MoMs did not differ significantly between women with inherited and women with acquired thrombophilia (0.88 vs. 0.99 MoM, P = 0.403). Conclusions: The triple test serum markers may be altered in thrombophilia patients treated with LMWH. Clinicians should consider offering these patients the first-trimester nuchal translucency test and other sonographic markers that are probably unaffected by the underlying maternal disease and/or treatment modality.