premature birth (EFO_0003917) is cHILDBIRTH before 37 weeks of PREGNANCY (259 days from the first day of the mother's last menstrual period, or 245 days after FERTILIZATION). Also known as: Birth, Premature, Birth, Preterm, Births, Premature, Births, Preterm, Premature Births, Preterm Birth, Preterm Births.