OB Exam 1 - Summary Maternity and Pediatric Nursing Concepts Of Maternal-Child Nursing And Families OB Exam 1 Antepartal Assessment and Care Antepartum is the time of pregnancy until the time of birth Trimesters of pregnancy o First trimester: 0-12 weeks o Second trimester: 13-28 weeks o Third trimester: 29-40 weeks The average pregnancy lasts 280 days from the first day of the last menstrual period (266 days from time of ovulation), 9 calendar months, 40 weeks Nagele’s Rule pg. 404 is...