The rhythm method of contraception now works as well as the pill, experts claim. An improved version of the previously unreliable birth control technique is now 99.6 per cent effective, they said.

But the system — only having sex when the woman’s menstrual cycle prevents her getting pregnant — must be followed to the letter.

The revised method requires a woman to frequently measure her temperature and other body signs.

Gynaecologist Petra Frank-Hermann studied 900 women — and just one in 250 had an unplanned pregnancy per year when using the method correctly.

But she admits it takes three months to master it — after using the method herself.

She said: “You need a book to learn or have proper teaching. But it’s like riding a bike — once you’ve learned it you won’t forget.”

Her research was published in the journal Human Reproduction.

Toni Belfield, of the Family Planning Association, said it shows the value of “natural family planning when combining two or more fertility indicators.”

Via the Sun