How do I know if I'm pregnant?

Reviewed by Dr Philip Owen, consultant obstetrician and gynaecologist

What are the first signs of pregnancy?
For most women, the first sign of pregnancy is when their periods stop. Although the absence of menstruation can be caused by many things if, in addition, a woman's breasts feel swollen or tender and she feels nauseous - especially in the morning - it is likely that she is pregnant.

How can pregnancy be confirmed?

The normal way to test for pregnancy is through a urine test.

This can be done at home using a pregnancy testing kit that can be bought over the counter from your local pharmacy.

A GP or Family Planning Clinic will do a pregnancy test.

How soon can a pregnancy test be done?
A woman can take a pregnancy test just a few days after her missed period.

How can you calculate when the baby will be born?
Conception takes place around the time of ovulation when the egg is released from the ovary. Ovulation takes place midway through the menstrual cycle, on about the 14th day if the first day of menstruation is taken as day one.

The beginning of a pregnancy is calculated from the first day of the last period. A normal pregnancy will last 40 weeks in total and it is not too difficult to estimate the date on which a woman can expect to give birth.

If, for example, the first day of her last period was April 1, add one week - April 8. Then add nine months to find the date of the birth. In this case it will be January 8 the following year. But for an accurate prediction, the period must have occurred regularly with approximately four weeks between the last two periods.

What if I have just come off the Pill?
If a woman gets pregnant within a couple of months of coming off the contraceptive pill she may experience irregular ovulation and irregular periods or even none at all.

Under such circumstances it is difficult to estimate the baby's due date reliably and an ultrasound examination is more useful.

An ultrasound scan performed in the first half of pregnancy will give the most reliable and accurate estimate of when the baby is due by working out the size of the foetus. Every maternity hospital will provide this as a routine service to pregnant mothers.