If you want to improve your chances of conceiving, the place to start is your diet and lifestyle. Dr Sarah Brewer, author of Planning A Baby: A Complete Guide to Preconceptual Care, explains how

Food, glorious food
You've heard it all before, but it really is crucial to eat a healthy diet supplying at least five servings of fruit and vegetables per day, and preferably eight to ten for vitamins, minerals, trace elements and antioxidants. As a nutritional safety net, you may like to take a multivitamin and mineral supplement especially designed for pregnancy or pre-pregnancy, too.

Weighty issues
Women in the healthy weight range for their height find it easier to conceive spontaneously than those who are significantly under or over weight. Why being overweight affects ovulation and fertility is not fully understood, but is thought to involve effects on hormone balance, insulin resistance and glucose control. Weight loss in sub-fertile women who are overweight increases the chance of both spontaneous conception and conception after fertility treatment. However, you should avoid sudden weight loss and crash dieting which is harmful for the health of you and your baby. Gradual, maintained weight loss will mean you're onto a winner.

Get moving
Regular exercise can boost fertility, especially if you are overweight, by improving insulin resistance and glucose control. Aim to take at least 30 minutes of exercise every day that is brisk enough to raise a light sweat and leave you slightly breathless. If you are relatively unfit, start your fitness programme with a brisk, walking regime.

Have a check-up
Have a sexual health check-up at a genito-urinary medicine (GUM) clinic. Some sexually transmissible infections, such as Chlamydia, may cause few symptoms but can reduce fertility if allowed to progress to pelvic inflammatory disease. A common vaginal bacterial imbalance (bacterial vaginosis) can increase the risk of miscarriage and pre-term labour as much as five fold.

Smoke signals
If you smoke, do your utmost to stop. If you cannot stop, then at least cut right down. Women who smoke ten or more cigarettes per day are three times more likely to experience difficulty in conceiving than non-smokers.

Ban the bottle
Try to avoid alcohol altogether during the preconceptual care period and for at least the first three months of pregnancy, if not throughout the whole nine months. Alcohol is a cell poison that becomes concentrated in the cells of a developing baby to produce higher levels than those found in the mother, and can interfere with rapidly dividing cells. It can also reduce fertility. One study found that women who drink five or less units of alcohol per week were twice as likely to conceive within six months than those drinking ten units per week or more.

Relax and unwind
Avoid excess stress which can affect fertility by lowering levels of sex hormones. In some cases, the effects of stress are severe enough to cause loss of menstruation. High stress and anxiety levels can also affect the outcome of fertility treatments. Take regular time out for rest and relaxation, even if it's just getting up from your desk and making a cup of tea, taking a quick walk a lunch time, or arranging to meet a friend for dinner.

Supplement your diet
Take a folic acid supplement, starting at least a month before trying to conceive. Folic acid is essential for normal cell division, especially during early pregnancy. As well as protecting against certain developmental abnormalities such as spina bifida, some researchers suggest that it may boost fertility, so that if you conceive twins, it is more likely that both embryos will survive and continue to develop, although this is controversial. Synthetic folic acid (found in supplements and fortified foods such as breakfast cereals) is more readily absorbed and used in the body than the natural folate form.

Don't take unnecessary risks
Avoid any non-essential drugs, herbs and other supplements as their effects on fertility are not always known. Some herbs, such Agnus castus, may be prescribed by a herbal medicine practitioner to boost fertility. Only use them under supervision, however.

Make predictions
Your most fertile time of the month lasts for the six days up to, and including, the day of ovulation. However, the timing of ovulation is highly unpredictable, even in women whose cycles are regular. When around 700 menstrual cycles were assessed among 221 women trying to conceive, only 30 per cent had their fertile phase entirely between day ten and day 17 of the cycle (the first day of the last period is counted as day one). Most women reached their fertile window earlier, and others much later. At least ten per cent of women were fertile on any given day between days six and 21, and up to six per cent were potentially fertile even on the day their next period was due. Using an ovulation predictor kit can increase your chances of achieving pregnancy.

And for him...

Get your partner to:

• Wear loose, cotton, boxer shorts rather than tight pants made from man-made fibres. These lower sperm count by up to 20 per cent
• Eat a diet rich in natural antioxidant vitamins C, E, betacarotene and zinc, and consider taking supplements containing these
• Stop smoking. Male smokers are only half as fertile as non-smokers
• Lower alcohol intake. Forty per cent of male infertility is linked with just a moderate alcohol intake

More information is available in my book, Planning a Baby: A Complete Guide to Preconceptual Care (Vermilion, £8.99).