When it comes to starting a family, timing is everything

The review, conducted jointly with researchers from Oxford University, the Royal Berkshire Hospital in Reading, and the Princess Anne Hospital in Southampton, included seven randomised controlled trials involving 2,464 women or couples who had been trying to conceive.

Each month there is a narrow window for successful conception due to the limited lifespan of the sperm and egg, which begins from around five days before ovulation (egg release) and lasts until several hours afterwards.

The period of a woman's cycle can be identified by different methods, including urine ovulation tests (dipstick devices that can detect changes in hormones released into the urine, signifying when ovulation will occur), fertility awareness-based methods (FABM) (including calendar tracking, monitoring changes in cervix fluid and body temperature) or identifying when the egg is released on ultrasound. This review aimed to assess the benefits and risks of timed intercourse on pregnancy, live birth, negative effects and quality of life in couples trying to conceive.

The study found that timing intercourse around the fertile period using a urine ovulation test increased the chances of pregnancy and live birth to between 20% to 28%, compared to 18% without using urine ovulation tests. This was specifically in women under 40 trying to conceive for under 12 months.

Tatjana Gibbons, a DPhil researcher at Oxford's Nuffield Department of Women's & Reproductive Health and lead author on the study, said: ''Many couples find it difficult to achieve a pregnancy, which can lead to concerns about their fertility.'

'The finding that a simple and easily available urine test can increase a couple's chance of successful conception is quite exciting because it can empower couples with more control over their fertility journey and could potentially reduce the need for infertility investigations and treatments.'

Professor Christian M Becker of Nuffield Department of Women's & Reproductive Health said: 'The high threshold of evidence required in a Cochrane review makes even this moderate quality evidence for the effectiveness of urine ovulation tests quite impressive, as well as surprising considering how long they have been available for.'

However, the researchers cautioned that because many of the studies were funded by the manufacturers of the urine ovulation test, the results should be interpreted with caution.

They also found that there was insufficient evidence to conclude the effect of the other methods in the study, including timed intercourse on clinical pregnancy (ultrasound-confirmed pregnancy), the use of FABM in timed intercourse compared to intercourse without ovulation prediction.