PROJECT SUMMARY The Eunice Kennedy Shriver NICHD Maternal-Fetal Medicine Units (MFMU) Network is a collaboration between fourteen Clinical Centers, the Data Coordinating Center (DCC) and the NICHD. Each clinical center is led by a Center Principal Investigator who is experienced in perinatal research and completion of both observational studies and clinical trials. Each clinical center also has a full-time Research Coordinator dedicated only to MFMU Network studies. Robust clinical research infrastructure is maintained to ensure successful participation in all MFMU studies. Each clinical center consists of one or more performance subsites. The number of sites in a center varies, for a total of 38 separate hospitals in this current funding cycle representing over 175,000 deliveries annually. The MFMU conducted the Prematurity Registry which was an Observational Cohort Study of Obstetrical Determinants of Preterm Delivery and Neonatal Outcome. This study was conducted between 2021-2022 and included all liveborn and stillborn infants with a gestational age at delivery between 16 weeks 0 days and 34 weeks 6 days. The data collection period was limited to January 1, 2019 to August 31, 2019 due to budget restrictions. The primary objective of the Prematurity Registry was to examine obstetrical determinants for a neonatal morbidity and mortality composite among women with an early preterm delivery. The Neonatal Research Network (NRN) has two ongoing registries, the Generic Data Base study (GDB), and the All Birth Cohort (ABC) Study. The aims of this project are Aim 1: To collaborate with the Neonatal Research Network on the identification and standardization of core data elements for maternal-neonatal registries. Aim 2: To design the optimal cohort of patients for which to collect maternal and neonatal outcomes. Aim 3: To pilot the core data elements on a subset of centers participating in both the MFMU Network and Neonatal Research Network.