Obstet Gynecol 2020 10;136(4):756-764
Maternal and Child Health Research Center, Department of Obstetrics & Gynecology, and the Clinical Microbiology Laboratory, Department of Pathology and Laboratory Medicine, University of Pennsylvania, Perelman School of Medicine, the Division of Genetics and Metabolism, Children's Hospital of Philadelphia, and the Department of Pediatrics, Biochemistry, and Biophysics, University of Pennsylvania, Philadelphia, Pennsylvania.