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.