Evaluation of Low-Molecular-Weight Heparin Treatment on First- and Second-Trimester Screening Test Results

Background The serum markers used in first- and second-trimester screening tests can be affected by different causes such as smoking, infertility treatment, and the presence of diabetes mellitus, which should be considered by obstetricians when giving information to patients. Low molecular weight heparin (LMWH) has a critical importance in the prophylaxis of deep vein thrombosis both in the antenatal and postnatal period. The aim of the current study is to investigate the effect of LMWH use on the first- and second-trimester screening results. Methods A retrospective analysis in our outpatient clinic between July 2018 and January 2021 of first- and second-trimester screening test results was conducted to assess the impact of LMWH treatment for patients with thrombophilia who started LMWH after pregnancy was detected were included. Test results were obtained as a multiple of median (MoM) combined with ultrasound measurements, maternal serum markers, and maternal age in addition to the nuchal translucency first-trimester test. Results The pregnancy-associated plasma protein-A (PAPP-A) MoM was lower and alpha-fetoprotein (AFP) and unconjugated estriol (uE3) MoMs were higher in patients treated with LMWH than in the control group (0.78 MoM vs 0.96 MoM; 1.00 MoM vs 0.97 MoM; and 0.89 MoM vs 0.76 MoM, respectively). Human chorionic gonadotropin (HCG) levels did not differ between groups at either time point. Conclusions Treatment of pregnant women with LMWH for thrombophilia may change the MoM values of serum markers for both first- and second-trimester screening tests. Obstetricians should be aware of this when advising screening tests to thrombophilia patients and should consider offering fetal DNA tests for this group instead.