Due date calendar

27 Jul

Due date calendar

The pregnancy due date is an estimated date when the baby is expected to be born. It can be calculated accurately to within a few days in women who have highly regular menstrual cycles. However, the due date is only a prediction, and the actual date can vary from days to weeks as the underlying processes of gestation determine childbirth. Doctors often use the last menstrual cycle date or the date of conception to estimate the due date.

How is the due date calculated?

There are different ways to estimate the due date both manually and by using a pregnancy due date calculator. These are the three most commonly used methods to calculate the due date:

Calculating from the first day of the last period

Women who have had regular periods before pregnancy can have their due date estimated using the date of the last menstrual period. Most doctors count 40 weeks from the first day of the last menstrual period to arrive at the due date. This method is most applicable to women who have regular 28-day menstrual cycles. Since they go into ovulation two weeks after the first day of their last period, the cycle started two weeks before they conceive. Therefore when the cycle is considered, it adds up to 40 weeks instead of 38 weeks.

Calculating from the date of conception

Women who precisely track their ovulation using the symptoms of ovulation predictor kits can estimate their due date based on the conception date. A pregnancy due date calendar by conception can then be made to keep track of the milestones as the weeks go by.

IVT transfer date

Women who conceive through IVF can calculate their due date by using the IVF transfer date. If it were a day-5 embryo transfer, then adding 261 days will give the due date. If the embryo transfer was on day 3, then adding 263 days gives the due date.

When is ultrasound used to calculate the due date?

Ultrasound scans are used to determine the due date when the woman has had irregular menstrual cycles. Since all the features of the fetus grow at a predictable and consistent rate, ultrasound scans are the most accurate way to determine the due date. Regardless of when the woman recalls having her last period, the ultrasound scan can precisely show the growth of the fetus, and the age determined by it is more accurate. It is because, in women who have irregular menstrual cycles, ovulation is hard to determine because of which the due date calculation can have errors.

How accurate is the due date?

Since a number of variables contribute to the actual date of delivery, the due date can only be approximated. Only 1 in 20 women delivers on her due date, while the rest can deliver anytime two weeks before or after the date.

Conclusion

The pregnancy due date calendar can be made using an estimated date based on the day of conception, the first day of the last period, or the IVF transfer date. However, an ultrasound scan can give the most accurate data based on fetal development.

References:

https://intermountainhealthcare.org/blogs/topics/intermountain-moms/2015/12/how-are-due-dates-calculated/

https://www.babycenter.com/pregnancy-due-date-calculator