A baby's due date is estimated from the expecting mother's last ovulation and menstruation, rather than the date of conception. Doctors must make many assumptions in these calculations, and many factors can affect the duration of a pregnancy. A combination of due date calculators and probe ultrasound gives the best possible estimate of a baby's due date.


1. How Is Pregnancy Measured?

When expecting a child, specific developments occur in order, serving as checkpoints from conception to labor and delivery. A pregnancy is measured in weeks within three trimesters. The first trimester includes weeks zero to 12. The second trimester covers the 13th to 24th weeks. Finally, the third trimester encompasses weeks 25 to delivery. After 37 weeks of pregnancy, the baby is considered full-term, and most babies are born between 37 and 40 weeks. Knowing the week of a pregnancy at each checkup helps healthcare providers determine if mother and baby are healthy and progressing normally.

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