How do I calculate my due date? Is pregnancy actually NINE months long?

due date

While we all think that it takes nine months for a woman to grow a baby inside her womb, it is not exactly right.

It takes about 38 weeks from the day you conceive to the day you deliver, which does not come up to nine months.

It is very difficult for a mums-to-be to know exactly when they conceived. If you have had sex just once during your fertile period you may not have actually conceived then. The sperm might have just stay in the fallopian tube for a few days until the egg comes its way – fertilisation happens, and it is then that the baby is conceived.

If that sounds a bit too complicated, there is a way of working out the due date.

While mostly people just estimate, doctors count from the first day of your last period. If you have a regular menstrual cycle, at an average length, that day is usually about two weeks before conception; this is why pregnancies are said to last 40 weeks – almost 10 months than the nine we usually refer to.

Your doctor will add 280 days from conception (40 weeks).

There is the added warning that this method does not take into account how long your menstrual cycle is.

How to work your due date?

Let’s get the facts in place, only 1 in 20 women delivers on her due date so this is just a rough calculation.

If you don’t know when you conceived

Take the date of the first day of your last period. Add 40 weeks.

If you do know when you conceived

Just add 38 weeks from your conception date.

Quick way to work out by month

This method is really simple (due dates can vary as this is a rough calculation):

January – October

February – November

March – December

April – January

May – February

June – March

July – April

August – May

September – June

October – July

November – August

December – September