计算预估预产期和孕期里程碑
This calculator uses Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period, adjusted for your cycle length. This is the most widely used method for estimating due dates.
Note: Only about 4% of babies are born on their exact due date. Most arrive between 37-42 weeks. Your healthcare provider may adjust the due date based on ultrasound measurements.