August 23rd, 2011 by Hasham

Pregnancy due date calculator

Work out when your baby is due

Pregnancy normally lasts from 37-42 weeks from the first day of your last period. Use our due date calculator to work out when you might expect your baby to arrive. This will give you a rough idea. As part of your antenatal care, your midwife will also offer you a dating scan that will give you a more accurate date for the birth of your baby.

Pregnancy Due Date

You can use this calculator to determine an approximate date your baby will be born. Don’t go printing those dated birth announcements just yet, though. Since it’s not always possible to determine the exact date of conception, most due date calculators, such as this one, are based on a gestational period of 40 weeks from the first day of a woman’s last menstrual period (LMP). This assumes a woman ovulates and conceives exactly two weeks after the first day of her LMP and carries the baby for 38 weeks. The problem is, of course, that this is an estimate, and 40 weeks is only an average term of pregnancy.

A normal pregnancy can last anywhere between 38 and 42 weeks. Many obstetricians will use what is called “Naegle’s Rule” to determine the approximate due date: Take the first day of your last period, and count back three months, then add seven days. For example, a LMP of January 1, 2001 would give you an approximate due date of October 8, 2001 (an even 40 weeks ahead).

How is my due date calculated?

The start of your pregnancy is actually calculated from the start date of your last menstrual period (LMP), or day 1 of your cycle. Given this method of calculation, your pregnancy is measured in what is termed gestational weeks, as opposed to being measured from the actual day of conception.

Counting from the first day of your LMP, there are 40 gestational weeks of pregnancy. Assuming that you have a 28-day cycle, in gestational weeks 1 and 2, your baby is waiting to be conceived. On day 14, and at the start of gestational week 3, your baby has just been created. By the end of gestational week 3, the actual age of your baby is one week.

Please remember that your baby will come when it is ready, so this result is an estimate only. Be sure to consult your healthcare provider to determine your correct due date.
Find more information in our Pregnancy & Birth section:

* Essential Baby Pregnancy Guide iPhone App
* Pregnant? What to do next…
* The first trimester
* The second trimester
* The third trimester
* Buying for baby
* Building a maternity wardrobe
* Stretch marks
* Quick food safety checklist
* Tips for a healthy pelvic floor
* Complications in pregnancy
* Sex during pregnancy

Discuss trying to conceive with other women in our Conception Forums:

* Pregnancy: Tips, Qs and Information
* What Month are You Due?
* Hospital and Birthing Centres
* Doulas & Midwives
* Baby Names
* Pregnancy/Parenting After Problems Conceiving
* Pregnancy/Parenting After Loss
* Specialised Pregnancy Support Groups