How old are you?
The traditional view is that a man can become a father well into old age, but new research suggests there's a "best before" time, just as for women. Studies from France in 2008 showed that men over 35 are more likely to make sperm with damaged DNA. This can make conception take longer, and can even increase the chance of miscarriage.
Score 0 if you are over 35. Score 5 if you are 35 or less.
Do you smoke?
Cigarette smoke can damage sperm, and reduce their swimming speed. Smoking also contributes to erection problems, with an obvious impact on fertility. The damage to health isn't always linked with how much you smoke.Score 0 if you're a smoker. Score 5 if you're a non-smoker, or stopped smoking at least 90 days ago (the time it takes to produce new sperm).
How much do you booze?
Alcohol can lower levels of the male hormone testosterone, and therefore inhibit sperm production. This can happen to even moderate drinkers. And of course drink can affect erections too.
Score 0 if you regularly drink 3 units or more a day. Score 5 if you drink less than this.
Have you had an STI?
Chlamydia and gonorrhoea can both block the epididymis, the delicate pipework that carries sperm from the testicle, causing permanent fertility problems. Gonorrhoea often causes a discharge from the penis, but chlamydia doesn't necessarily. Around one man in eight has chlamydia, and at least half of them have no symptoms.
Score 0 if you have had chlamydia or another STI, or have never had a test. Score 5 if you had a negative test, or had prompt treatment.
What's your weight?
Being overweight can reduce levels of testosterone, and therefore lower the sperm count. Studies also suggest that being underweight can have a similar effect on sperm.
Score 0 if your BMI is over 29 or under 20. Score 5 if your BMI is between 20 and 29.
Do you take drugs?
A few medicines, including drugs for cancer, can affect sperm production temporarily, but it can sometimes be permanent. Anabolic steroids - the kind banned in sport - suppress sperm production. Most street drugs, including coke, cannabis, ecstasy and heroin, can lower the count and cause abnormal sperm. Cannabis can also make sperm too sluggish to fertilize an egg.
Score 0 if you take recreational drugs now or have taken any in the last 3 months. Otherwise score 5.
Do you get overheated?
Sperm production is sensitive to heat. The testicles work best at a steady temperature of 32 C (89.6F), which is why they're housed in the relatively cool scrotum. Boxer shorts made of cotton help keep your sperm factory at an ideal temperature. Tight synthetic underpants, frequent hot baths, and using a laptop a lot can all reduce the sperm count by up to 25 per cent.
Score 0 if you have long hot baths, wear tight briefs or use a laptop for more than around 30 minutes a day. Otherwise score 5.
How much do you exercise?
An active lifestyle is good for health and can help conception, but over-training can drastically reduce the sperm count. If you often run marathons or you exercise vigorously for over an hour a day, your fertility could be halved.
Score 0 if you're either a couch potato or an exercise addict. Otherwise score 5.
Are you stressed?
Over time, serious stress can affect several hormones, including those that control sperm production. Life can't be entirely stress-free, but you can learn to manage stress. Some men benefit from anger management classes, while others just need to make more time for leisure and exercise.
Score 0 if you feel constantly stressed. Score 5 if you think you're coping well.
Have you had a problem with the testicles?
A number of infections and disorders can affect fertility. Mumps can cause the testicles to become inflammed and infected, but this rarely affects fertility. Injuries to the testicle (as in sport) and operations for undescended testicle are more common, because these can damage blood flow to the testicles. A condition called varicocoele (like a knot of varicose veins on the testicle) may also reduce fertility. If you think your testicles have changed in any way, see your GP.
Score 0 if you have had an op or serious injury to the testicle. Otherwise score 5.
Analysis
If your score is under 20
The odds look low right now. On the plus side, you can make lifestyle changes, so there's everything to play for. Not all the risk factors are equally vital to every man. If you're overweight and take drugs, getting clean is far more important. See your GP or practice nurse for support and advice that's tailored to you.
If your score is between 20 and 40
Your chances of fatherhood are about average, but you can boost them by changing any bad habits that are affecting your fertility. Your practice nurse can help with stopping smoking or with reaching your ideal weight.
If your score is over 40
You're in good shape. As a rough guide, if a young couple have regular sex, there's a one in 5 chance of pregnancy every month. You're likely to conceive within six months, but it's not a certainty because there's an element of luck. Bottom line? If you want a baby, all you can do is keep trying.
