Simply it is the term used medically to calculate how far along your pregnancy is. It is calculated in weeks and measured from the first day of your last menstrual cycle to today’s date or the day of your appointment.

Of course, not all of us keep track of our first day of menstruation religiously. So what happens in these common cases? When you come for an ultrasound pregnancy scan, the sonographer will be able to tell the gestational age of your fetus.

This is calculated by measuring the diameter of the gestational sac or CRL – the length of the fetal pole. If you’re curious about how we do this during your ultrasound scan, here are some example of the formula:

We take the mm measurements of your fetus’ gestational sac and add this to 4 weeks/28 days. This gives you a general estimate of gestational age. So for example, if the sac measures 5mm, we add this to 28 and get a total of 33 days, which would be 4 weeks and 5 days in total. Also, charts have been developed to illustrate and calculate this.

What is the pregnancy wheel?

A pregnancy wheel is a small circular calendar that is also referred to a gestation calculator. By using your LMP – last menstrual period, the pregnancy wheel can calculate your estimated due date. Simple move its pointer to your LMP rotating the wheel to show the estimated due date.

Image credit for pregnancy wheel FaceMama