Estimating Gestational Age

What is gestational age?

Gestational age is the age of your unborn baby.

How is gestational age calculated?

The age of your baby and your due date is estimated to be 40 weeks from the day you started your last period. An early exam of your uterus and an early positive pregnancy test can help determine your baby’s age and due date.

Ultrasound can be used to confirm your baby’s age. An ultrasound uses sound waves to show pictures of your baby. Your baby can be measured with ultrasound as early as 5 or 6 weeks after your last menstrual period. This method is most accurate during the first half of pregnancy.

Why is it important to know the gestational age?

There are many reasons why it’s important to know your due date and how far along your pregnancy is. Some reasons are:

  • At specific weeks of pregnancy, certain things are expected–for example, hearing the baby’s heartbeat for the first time (with a stethoscope) and feeling your baby move for the first time. If these things happen when expected, they can be a sign that your baby is doing well.
  • Checking the growth of your baby can be done accurately only if your baby’s age is correctly known.
  • Some tests should be done at certain times in the pregnancy.
  • It’s very important to know your baby’s age if there are complications with the pregnancy and your baby needs to be delivered early.
  • It’s important to know when your baby is overdue so the health of the baby can be watched more closely.
Developed by RelayHealth.
Adult Advisor 2015.1 published by RelayHealth.
Last modified: 2014-02-07
Last reviewed: 2014-02-05
This content is reviewed periodically and is subject to change as new health information becomes available. The information is intended to inform and educate and is not a replacement for medical evaluation, advice, diagnosis or treatment by a healthcare professional.
Copyright ©1986-2015 McKesson Corporation and/or one of its subsidiaries. All rights reserved.

Patient Portal

myTuftsMed is our new online patient portal that provides you with access to your medical information in one place. MyTuftsMed can be accessed online or from your mobile device providing a convenient way to manage your health care needs from wherever you are.

With myTuftsMed, you can:

  1. View your health information including your medications, test results, scheduled appointments, medical bills even if you have multiple doctors in different locations.
  2. Make appointments at your convenience, complete pre-visit forms and medical questionnaires and find care or an emergency room.
  3. Connect with a doctor no matter where you are.
  4. Keep track of your children’s and family members’ medical care, view upcoming appointments, book visits and review test results.
  5. Check in on family members who need extra help, all from your private account.


Your privacy is important to us. Learn more about ourwebsite privacy policy. X