Labour & due date

Is pregnancy really 9 months?

Checked against the sources listed on this page. Not reviewed by a clinician. Last updated 5 November 2026. How we check.

Partly true

Roughly. It is 40 weeks (280 days) from the first day of your last period, which is about 9 months and 1 week. From conception it is about 38 weeks.

Because months vary in length, “nine months” is an approximation. Clinicians use weeks and days because they are precise.

References

  1. MedlinePlus (US National Library of Medicine): Fetal development

Related weeks

Week 1Week 40

More labour & due date myths

Myth

Will my baby be born on the due date?

Unlikely. Only about 4% of babies arrive on their exact due date. Most are born within about two weeks either side.

 Myth

Can spicy food or pineapple bring on labour?

There’s no good evidence that spicy food or pineapple starts labour. Some small studies suggest eating dates late in pregnancy may help the cervix ripen.

 Myth

Does a full moon bring on labour?

No. Large studies of hundreds of thousands of births found no link between the lunar cycle and when babies are born.