Maternal serum soluble HLA-G levels in missed abortions

BACKGROUND AND OBJECTIVE. It is unclear how immune tolerance develops to a semiallograft fetus in pregnancy. Human leukocyte antigen G (HLA-G) expressed by extravascular trophoblasts plays an important role in the recognition of the gestational tissues as self and the development of immune tolerance against the gestational tissues by the maternal immune system. The soluble form of the HLA-G (sHLA-G) molecule in the maternal serum is also reported to contribute to the prevention of rejection during pregnancy. The aim of the study was to compare the maternal serum sHLA-G levels of the women with missed abortions and control subjects with uncomplicated pregnancies. MATERIAL AND METHODS. The prospective cross-sectional study involving 40 with missed abortions and 40 control women, matched by age, gestational age, and body mass index, was carried out. The study group consisted of the women with singleton pregnancies, who were diagnosed with a missed abortion. Only the patients who were confirmed to have an uncomplicated term delivery during follow-up were included in the control group. The serum sHLA-G level was compared between the groups. RESULTS. There was no significant difference in the mean serum sHLA-G levels in terms of gravidity (P=0.761) and a history of abortion (P=0.379) in the control group. The median serum sHLA-G level in the missed abortion group was significantly lower compared with the control group (16.8 [8.5-35.8] vs. 26 [11-135] U/mL, P<0.001). All the women in the control group had uncomplicated term deliveries. CONCLUSION. Our results showed that the women with missed abortions had significantly lower serum sHLA-G levels compared with the healthy pregnant controls, which may have potentially played a role in the impairment of physiological immunological tolerance during pregnancy. However, the determination of the exact role and the potential clinical utility of maternal serum sHLA-G for the detection/prediction of a missed abortion risk requires further detailed studies.