Getting the best out of a pregnancy calendar

Like everything else, garbage in = garbage out. These calculators and calendars work off the last period you had before you became pregnant.

If you don't know this date, it will be more difficult to estimate your due date. The calculation is based on the fact that conception most likely took place about 1 week after the first day of your LMP (last menstrual period). The gestational period is then about 9 months from that date

These calculations are only estimates. About 80 percent of babies are born within ten days of the due date. That leaves a fairly large window for error - about 10 days either side of the estimated date (20 days) and that is for 80% of pregnancies - there is another 20% which are earlier or later again.

Your doctor will be able to give you updated due dates based on scans of your developing baby . The measurements taken of the baby during these scans can be used in calculations to re-evaluate the estimated due date.

Many women have their baby before their term date. There are a number of factors which can contribute to them not delivering close to their pregnancy due date. These factors include
* Multiple pregnancy - twins, triplets
* An abnormally shaped uterus that may crowd the fetus
* Placenta previa
* High fever or severe infections in the mother
* Placental abruption
* Smoking during pregnancy
* Untreated diseases of the thyroid gland in the mother
* High blood pressure, diabetes, and kidney disease and other pregnancy complications in the mother

About the Author

This article is written by Babypar, author of pregnancy calendar on Baby-Parenting.com