Postpartum maternal thrombophilia workup value in pregnancies with severe small for gestational age.

Introduction: In the absence of prenatal etiology explaining small for gestational age (SGA), a blood workup may be performed postpartum to look for maternal thrombophilia if a newborn is confirmed to be growth-restricted at birth. The literature regarding thrombophilia factors and fetal growth restriction is discordant. The main objective was to assess the prevalence and type of maternal thrombophilia among women delivering newborns of birthweight below the 3rd percentile and undergoing a postpartum thrombophilia workup and placental analysis.

Material and methods: This was a single-center retrospective observational cohort study in a tertiary care French maternity. The study population included all women delivering a liveborn infant with severe SGA, defined as a birthweight below the 3rd percentile according to French charts between January 2014 and December 2018. Data from thrombophilia workups (antiphospholipid antibodies, protein C assay, protein S assay, antithrombin assay, factor V Leiden mutation, and factor II G 20210A mutation search) were collected from medical records. Placental pathology analysis, if available, was also collected. The primary endpoint was the prevalence of positive expanded thrombophilia workup (inherited or acquired).

Results: A total of 733 patients were included in our study, 401 of whom (54.7%) underwent a postpartum thrombophilia workup. The overall prevalence of hereditary thrombophilia was 6.7%, 95% confidence interval (4.3 to 9.2) and of acquired thrombophilia was 2.0%, 95% confidence interval (0.6 to 3.4). Among hereditary anomalies, heterozygous factor V mutation and heterozygous factor II mutation were the most frequently observed, respectively, 4% and 1.7%. Concerning the presence of antiphospholipid antibodies, triple positivity was present in one patient (0.2%). The presence of a single antiphospholipid antibody was more frequently observed in 3 patients (0.7%).

Conclusions: Among patients with a severe SGA infant and postpartum investigation of maternal thrombophilia, an extensive workup of postpartum thrombophilia contributed to a low proportion of positive findings. This suggests that the prescription of such a workup should be targeted, based on personal and family medical history. In fact, testing for inherited thrombophilia should be reserved for patients with a personal or family history of thrombosis. Testing for antiphospholipid antibodies should follow ACR/EULAR criteria.