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What is gestational age?

Gestational age is the age of a pregnancy calculated as the number of weeks that have elapsed from the first day of the last normal menstrual period, according to the American College of Obstetricians and Gynecologists. Pregnancy is often described as being nine months long. However, doctors determine gestational age based on a 40-week period that is divided into three trimesters of about 13 weeks each.

Another key factor in determining gestational age is the estimated due date, which is calculated from the first day of your last menstrual period. If the first day of your last menstrual period was five weeks ago, your gestational age would be five weeks. Your doctor will use your gestational age to track your baby's growth and development and possibly to schedule tests throughout your pregnancy. Normal gestation can range from about 37 to 41 weeks, so estimated due dates are accurate for only about one out of every 20 pregnancies.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.