Scientists have devised a formula that predicts a woman’s chances of pregnancy.
The formula combines information about how fertility drops with age with the length of time a woman has been trying to start a family, to come up with their odds of conceiving.
For example, they have worked out that the average 25-year-old who has been trying to get pregnant for six months has a 15% chance of doing so in the following month.
By the age of 30, her odds are 13% and, at 35, they have dropped below 10%.
The speeding up of the biological clock mean the chances of pregnancy plummet after 35.
The average 40-year-old who has been trying for six months has just a 5% of getting pregnant in the next month – or odds of one in 20.
Scientists have devised a formula that predicts a woman’s chances of pregnancy
The calculations also show that when a woman is 25, it will take 13 months for her odds of conceiving quickly to fall below 10%.
But a 35-year-old woman has just six months before her chances are so slim.
The long-standing rule of thumb is that those trying for a family should wait a year before seeking help, although doctors are increasingly acknowledging the impact of age.
The researchers, from the University of Warwick and the London School of Economics in UK, say that more detailed information could make it easier for couples to discuss fertility issues with their GP.
Professor Geraldine Hartshorne said: “People feel embarrassed and upset and don’t want to go to the doctor. Men, in particular, can be a little bit reluctant.
“As time goes by and people have been trying for a while, they start to get stressed and upset and that can affect their chances of having sex and then becoming pregnant. Approaching a doctor about a personal matter is daunting, so knowing the right time to start investigations would be a useful step forward.”
Writing in the journal PLoS One, Prof. Geraldine Hartshorne also warns that taking too long to conceive could indicate that the resulting pregnancy might be risky.
The work could help doctors to decide whether to refer patients for costly and uncomfortable tests or advise them to keep trying for a baby a little longer.
The researchers have passed their work to the National Institute for Health and Clinical Excellence, which formulates health guidelines. In future, it may be possible to create an online calculator that provides couples with a personalized prediction.
Prof. Geraldine Hartshorne added that factors such as smoking or being fat are “not the most important things” when it comes to conceiving. However, a healthy lifestyle will boost the odds of a healthy baby.
She said: “If your tubes are blocked, giving up smoking really isn’t going to make a difference, but things like smoking and obesity do have important effects when you do get pregnant and in that respect they should be addressed as soon as possible.”
Researchers at Boston University have found that two cups of tea a day may help boost a woman’s chances of becoming pregnant.
The study found that women were 27% more likely to become pregnant if they regularly drank tea compared with those who did not.
However, the same research found consuming two cola-style fizzy drinks daily seems to reduce a woman’s prospects of conceiving – and it makes no difference if the cola is a diet or sugary version.
Women who drank these soft drinks at least twice a day reduced their chances of becoming pregnant by 20%.
There was no effect on the chances of pregnancy for women who preferred to drink coffee.
The findings were based on a group of 3,600 women who were actively trying to have a baby.
The study’s author, Professor Elizabeth Hatch, wanted to determine if caffeine intake had any effect on women trying for a baby. While there have been other studies on the subject, their results have not been conclusive.
They have also used methods which are thought to be unreliable, based on interviews with pregnant women who were asked to remember the amounts of tea, coffee and soft drinks they consumed before they conceived.
Instead, Prof. Elizabeth Hatch monitored each of the volunteers for a year.
Danish women were chosen for the research because every Danish citizen is given a civil registration number at birth, allowing health officials to recruit and then screen individuals through the internet.
The women, with an average age of 28, formed the largest group ever studied to evaluate a link between caffeine consumption and pregnancy.
Researchers at Boston University have found that two cups of tea a day may help boost a woman’s chances of becoming pregnant
Prof. Elizabeth Hatch said: “We found that women who drank tea two or three times a day did have a 27% increased chance of becoming pregnant. We don’t know how they took the tea or if they added milk or lemon, but they had this increased chance of getting pregnant over women who did not drink tea at all.
“It may be linked to caffeine but clearly there may be other factors linked with the women’s lifestyle or there may be beneficial properties in tea itself.
“I think drinking two or three cups of tea a day for anyone wishing to get pregnant will be fine. I would love to say tea is a miracle cure to get pregnant but that is not realistic. There may be other factors. The tea drinkers tended to be older women and there may be something else in their diet or lifestyle that helped.”
Green tea has previously been linked with increasing women’s chances of becoming pregnant.
However, in this study women were asked to record their consumption of green or herbal tea in the same section and no link with increased chance of pregnancy was found.
Further research will seek to identify whether drinking green tea helps women became pregnant.
Follow-up work will establish more about the health and size of the babies born to the tea-drinking mums and if the women endured shorter or longer pregnancies or suffered miscarriages.
