Protein C global assay evaluation in naturally conceived vs. assisted reproduction-achieved twin pregnancies: a prospective longitudinal study.

While protein C global assay levels drop during twin pregnancy, there is no difference between ART-conceived and naturally conceived gestations. Decreased levels of protein C global assay during the third trimester were similarly associated with perinatal complications in both groups. Our results imply that twin pregnancy of itself is a more dominant factor for perinatal complications as compared to other factors, such as subfertility or the exposure to ART per se.