Thrombophilia and immunological disorders in pregnancies as risk factors for small for gestational age infants

Objectives To determine if inherited thrombophilia and immunological disorders represent risk factors for small for gestational age infants, and to assess their relationship with neonatal status. Design Case-control study. Population Ninety-seven consecutive women who had pregnancies complicated by unexplained small for gestational age infants, defined as a birthweight below the third centile and 97 women as controls who delivered infants with a birthweight >10(th) centile. Methods Patients were included in the immediate postpartum period and tested for antithrombin III, protein C, protein S, anticardiolipin and antinuclear antibodies, lupus anticoagulant, Factor V Leiden mutation, prothrombin 20210A mutation, and methylenetetrahydrofolate reductase (MTHFR) polymorphism. Women with small for gestational age infants were then divided into subgroups depending on haemostatic and immunologic status in order to compare neonatal events. Results Frequencies for anticardiolipin and antinuclear antibodies were higher in women with small for gestational age infants compared with controls (P=0.02 and P=0.004, respectively), and overall prevalence of inherited thrombophilia were comparable in cases and controls (19.6% and 18.6%, respectively). The subgroups of patients with small for gestational age infants were women with only one inherited thrombophilia (n = 10), only one imunological disorder (n = 14), combined disorders (n = 9), and no detected abnormality (n = 64). Admission to paediatric ward significantly increased in the group with combined disorders (P=0.002) compared with the other groups. Also one-third of the babies from this group had a poor neonatal outcome. However, most of the neonatal deaths (6/7 = 85.7%) occurred in the group with no detected abnormality. Conclusion The prevalence of inherited thrombophilia was considered to be similar between the case and the control groups even when immunological disorders were significantly elevated in pregnancies complicated by the baby being small for gestational age. Combined disorders may represent a potential risk factor for severe small for gestational age infants. However, the aetiology of small for gestational age infants with poor neonatal outcomes remains unknown in most cases.