How Far Along Am I? Figuring Due Dates

Figuring out just how far along you are and when your due date will be can be pretty confusing. Most people say a pregnancy is nine months long, but others talk about it being 40 weeks long. If that’s true, doesn’t that mean a pregnancy is actually 10 months long? Well…since most months are slightly longer than four weeks, the answer is actually somewhere in the middle.

First things first. To figure out a due date, the first thing you need to determine is when you conceived. And that’s the tricky part. It’s estimated that ovulation happens somewhere between Day 11 and Day 21 of your cycle. Unless you’re taking your temperature daily, it’s unlikely that you will know precisely when you ovulate. To keep it simple, most doctors use the first day of your last period as the start of your pregnancy. From there it is simply a matter of adding 280 days (which is 40 weeks) to determine a due date.

If you were using the actual conception date, the pregnancy is actually about 38 weeks long.

Remember that the due date is just a guess. Only about five percent of babies are actually born on their due date.

An ultrasound gives you a good measure of how far along you are. Like doctors, sonographers will give their measurements estimating from the last menstrual period. Babies can usually first be measured using an ultrasound, as early as five to six weeks from the woman’s last period. The most accurate measurements are gotten between the eighth and 18th week of pregnancy. Ultrasounds are less accurate as babies get older because each baby grows at a different rate.

Your First Look offers free pregnancy tests and ultrasounds to confirm viability and gestational age. Since not everyone can remember precisely when their last period began, the ultrasound will likely give you a good idea of both gestational age and due date.