Inclusion criteria for the pregnant subjects included healthy singleton pregnancies. Exclusion criteria included maternal diseases like hypertension, diabetes mellitus and chronic disease, known infection like hepatitis or human immunodeficiency virus, maternal history of hypertensive diseases in previous pregnancy, and fetal genetic, chromosomal or intervention-requiring morphologic abnormalities. Inclusion criteria for non-pregnant controls were fair general condition, female sex, age ≥25 and ≤45 years and for blood donors fulfilling national criteria for blood donation. Exclusion criteria were current or previous systemic autoimmune disease, asthma, convalescence after major illness, surgery, current medication with corticosteroids, immunosuppressive agents, and malignant neoplasia or chemotherapy within 5 years before recruitment for the study.