How Long is a Pregnancy?

How long a pregnancy lasts seems to be straightforward, right?

We’ve all been told it’s 9 months.

In fact, this is actually just a rough guideline.

So how long is pregnancy, really?

If 9 months isn’t exactly correct – why do they say pregnancy is 9 months?

Very few mamas-to-be know exactly when they conceived, so doctors need to work from a different date when calculating your gestation period and the baby’s due date.

They start from the first day of your last period before a positive pregnancy result.

And, if you have an “average-length” period, at regular intervals, that day is usually 2 weeks before conception.

To support this, when you have your first ultrasound at around 12 weeks, the sonographer will confirm a due date based on the size of the baby.

This is usually more accurate than basing the due date on estimated dates, as women’s cycles and ovulation dates can vary.

All-in-all, a pregnancy lasts about 280 days. But how many weeks is a pregnancy?

Well, this works out at around 40 weeks – which is actually nearer 10 months!

And with that in mind, it’s good to be aware that babies usually arrive anytime between 37 weeks and 42 weeks.

In this article: 📝

Do babies arrive on their due date?

All pregnant women are given a due date for their baby to arrive, but only about one in 20 babies are actually born on their exact due date.

Many babies are born between 37 weeks and 41 weeks of pregnancy, often within a week either side of their due date.

For first time mamas, it’s extra common for baby to arrive after the official due date, so don’t worry.

Is 37 weeks considered full term?

Technically, yes, 37 weeks is indeed considered full term – but babies born before 39 weeks might have a higher chance of having breathing problems, low blood sugar, and other issues that may result in them needing some extra TLC after delivery.

What about giving birth before 37 weeks?

Of course, there are times that babies make their entrance before 37 weeks.

Doctors can help premature babies who arrive earlier than planned, as they’re likely to need additional care.

• Babies born at or before 25 weeks are “extremely” preterm.
• Babies born at less than 32 weeks are “very” preterm
• Babies born between 32 and 34 weeks are “moderately” preterm.
• Babies born between 34 and 36 weeks are “late” preterm.

Around 1 in 10 babies in the US are born premature each year.

What about if you go past 40 weeks?

As we mentioned earlier, going past your 40-week due date is nothing to be concerned about.

It’s very common – especially if it’s your first pregnancy.

But towards this latter stage of your pregnancy, you might be feeling cumbersome and uncomfortable, so it’s totally understandable if you feel like you want to fast-forward to your delivery.

The medical pros are there to offer support, monitor you and your baby carefully, and also to discuss an induction plan if you want to hurry things along and meet your little one.

A prolonged pregnancy is one that lasts longer than 42 weeks, and it does carry a higher risk of health complications. If you are overdue now and you’re anxious about medical intervention to start labor, then it’s worth speaking to your healthcare provider to get all the info.

➡️ Don't miss also our complete pregnancy week-by-week guide.