Maternal COVID-19 Serological Changes—Comparison between Seroconversion Rate in First and Third Trimesters of Pregnancy and Subsequent Obstetric Complications: A Cohort Study oleh Maria N. Rayo, Adriana Aquise, Irene Fernandez-Buhigas, Lorena Gonzalez-Gea, Coral Garcia-Gonzalez, Mirian Sanchez-Tudela, Miguel Rodriguez-Fernandez, Diego Tuñon-Le Poultel, Belen Santacruz, Maria M. Gil