Antiphospholipid Antibodies in a General Obstetric Population: Clinical Impact on Pregnancy Outcome and Relationship with the M2 Haplotype in the Annexin A5 (ANXA5) Gene

Antiphospholipid (aPL) antibodies are recognised risk factors for adverse obstetric outcomes. Recently, carriers of the M2 haplotype in the Annexin A5 gene have been shown to have a higher susceptibility to develop aPL antibodies. In a general obstetric population, we prospectively evaluated the possible relationship between: (1) aPL antibodies and M2 haplotype; and (2) aPL antibodies and/or M2 haplotype and obstetric outcomes. From a cohort of 3,097 consecutive pregnant women, 1,286 samples were analysed for the presence of both anti-cardiolipin and anti-human β2-glycoprotein I antibodies; samples with available DNA (n = 606) were also investigated for the M2 haplotype. Overall, 41/1,286 (3.2%) women showed the presence of aPL antibodies. Among them, 2 (4.8%) experienced a pregnancy loss and 38 (92.7%) gave birth to live-born babies (p-value = non-significant vs. those without aPL antibodies). M2 haplotype was identified in 140 (23.1%) out of 606 women with DNA available: 3/140 (2.1%) M2 carriers and 17/466 (3.6%) non-carriers tested positive for aPL antibodies, respectively (p-value = non-significant). In total, 15/150 (10%) M2 and/or aPL antibody carriers, and 38/445 (8.5%) non-aPL antibody and/or M2 carriers suffered from obstetric complications, respectively (p-value = non-significant). No relationship between aPL antibodies and M2 haplotype was found. Furthermore, neither aPL antibodies nor the M2 haplotype is associated with obstetric complications.