Longer Duration and Proper Titration of Low Molecular Weight Heparin (LMWH), Are Independent Factors for Successful Pregnancy Outcome. Retrospective Analysis from a Single Center
Authors: Stamou Maria , Intzes Stergios , Lamprianidou Eleftheria , Papoutselis Menelaos Konstantinos , Bezirgiannidou Zoe , Nakou Evangelia , Kartasis Zafeirios , Vrachiolias Georgios , Bazntiara Ioanna , Kotsianidis Ioannis , Spanoudakis Emmanouil 
Published: October 2019

Abstract
The role of thrombophilia and LMWH use in pregnancy loss (PL) and pregnancy complications (PC) is debated. In this retrospective study from a single center we analyzed the clinical outcome of pregnancies in relation to thrombophilic factors and the use of LMWH, aspirin and folic acid in 143 women followed up for a total of 173 pregnancies referred to our center from 2003 to 2016.
Methods: Women were referred to our unit for: more than 2 unexplained PL (n=96, 78 experienced only early PL, 11 had only late PL, 7 had both early and late), one pregnancy loss(n=45) or one pregnancy complication (placenta abruption, intrauterine growth restriction, eclampsia, n=2). Mutations in Factor V-Leiden (FVL, G1691A), Prothrombin (PTG, G20210A) and MTHFR (C677T, A 1206C) were checked by DNA hybridization Kit. Plasma levels of antithrombin-III, protein-C, free Protein-S, APCR, FVIII, FXII, PT aPTT, fibrinogen, homocysteine and La-test were measured by photometry (DACO). Anticardiolopin and anti-β2GPI antibodies (IGG and IGM) were measured by ELISA in serum (APLA). End points were live birth and pregnancy complications.
The prevalence of thrombophilia in our cohort was similar with previous studies and 34/143 (23,4%) women were negative for all thrombophilic factors. We observed mutations in FVL(11,6%), PTG (9,6%), MTHFR (homozygous or double heterozygous, 33,3%) and deficiencies of AT-III (3,3%), Prot-C (1,6%), Prot-S (8,8%), APS (8,7%). Combined severe trombophilic factors were found in 31 women (21,5%) (FVL+PTG 4/31, Natural Anticoagulants one out 3 Def + MTHFR 3/31, APS + MTHFR 2/31, FVL+MTHFR 16/31, PTG + MTHFR 6/31).
We then separated our cohort into women with <2 complications or women with >2 complications. The second group had significantly higher incidence of FVL mutation (12,5 vs 8,3%, p=0.05) and deficiencies of AT-III and Free Prot-S ( 6,5 vs 0 %, p=0.01) compared to the first one. By contrast, women in the first group had higher incidence of La-test (12,5 vs 4,5%, p=0,03), APLA ( 12 vs 6,6%, p=0.03) and Prot.C deficiency (4,5 vs 0%, p=0.01).
In univariate analysis both hereditary and acquired thrombophilic factors did not correlated with pregnancy outcome (live birth or pregnancy complications). Only age as a continuous parameter correlated negatively with live birth and positively with pregnancy complications (p=0.01 and p=0.025, respectively), whereas high BMI as a continuous parameter also negatively affected live births (p= 0.049). Logistic regression analysis reveals that the age of 35 is the cut off for unfortunate pregnancy outcome.
Pregnancies were proceeded with (n=143, 81,7%) or without (n=32, 18,3%,) LMWH. The decision to use LMWH were based in a positive thrombophilia screening test (n=84) or to prior history >2 pregnancy complications with negative trombophilia testing (n=59). Concomitant use of ASA was prescribed in 78 pregnancies (dose less than 100 mg/day) and concomitant follic acid in 143 pregnancies. The percentage of live births were identical in women treated with LMWH (87,4%) or not (87,5%, p=0.9). In multivariate analysis, the only factor that was strongly correlated to live birth was the duration of LMWH treatment (odds ratio, OR =3,567, 95% CI (1.845, 6,894), p= 0,01) and the titration of the dose with anti-Xa (OR=5,138, 95% CI (1,717, 15,376), p = 0,01, fig.1a). By ROC analysis the duration of LMWH which correlated to live birth was ≥ 5.5 months(fig. 1b). The addition of ASA was insignificant for live birth (p=0.7), while the duration (>6months) of follic acid also appeared to add a benefit in combination with LMWH (p=0.01). Moreover, pregnancies proceeded without LMWH exhibited higher rates of pregnancy complications (18,75 vs 11,2%, p=0.08) and prematurity (14,3 vs 8,8%, p=0.05).
In summary, our findings argue against hereditary thrombophilia screening in the cases of previous pregnancy loss or pregnancy complications. On the contrary, testing for APS even after the first event might be of value as this population often has laboratory evidence of APS and may benefit from proper anticoagulation. The use of LMWH and folic acid but not of ASA was related to less pregnancy complications or prematurity, whereas proper titration of LMWH by using anti-Xa and long duration of therapy were the only important factors for successful pregnancy outcome.

Disclosures
No relevant conflicts of interest to declare.