Forget books, special diets and particular times of the month. Couples who want a baby should put their energy into having the wild, uninhibited sex of their early days together.
The better their quality of love-making, the greater their chances of conception, scientists say. What one fertility expert calls "gourmet sex" - where both partners take time to ensure the other has a satisfying experience - gives a couple the best chance of producing a baby.
"Couples who are trying to have a baby often mention that the sex becomes a bit of a chore, a bit mechanical and routine. That's the wrong thing to be doing," said Dr Allan Pacey, a senior lecturer in andrology at Sheffield University.
"The sex should be as wild and thrilling as it was when they first met, when they weren't thinking about babies, to give them the maximum possible chance of having a baby," added Pacey, secretary of the British Fertility Society.
Men usually produce about 250 million sperm during intercourse. But those who are fully stimulated because they are enjoying "gourmet sex" will ejaculate up to 50% more than that, according to research revealed in a Channel 4 documentary tomorrow. An extra five minutes of sexual activity before ejaculation can produce an extra 25 million sperm, said Pacey. That, plus the fact the extra sperm released are of a higher standard, means there is a greater chance of the sperm and egg fusing to create a new life.
"The better the sex, the better the chances of conception," Dr Joanna Ellington, an American expert in reproductive physiology, says in the programme, The Great Sperm Race. "One of the things that men don't realise is that the more excited they are, the further back in the testicle they are going to draw on reserves [of sperm]. So if you have what I call 'gourmet sex', where you really spend time and you make it fun for both partners, that is going to make the man more stimulated and he is going to ejaculate more and healthier sperm."
The research tallies with previous studies showing men who have viewed pornography just before ejaculation also produce greater amounts of sperm.
For women, more orgasms equal not just more pleasure but also enhanced fertility. "When a woman experiences an orgasm, we think the intensity of the muscular contractions she has during the big pressure changes going on in her body helps to pull or suck up the sperm into her cervix and from there into the uterus," explained Pacey.
Research into female pigs underlines the beneficial effect. Danish researchers found that sows who are sexually stimulated by humans during artificial insemination had a 6% increase in fertility. "Having a farmer on the pig's back is low-tech and unsexy but it seems to work," said Pacey. The findings were so striking that Danish pig farmers are given a government-approved five-point plan showing them what to do.
The programme, a dramatisation of the epic journey sperm undertake in their quest to fertilise the egg, reveals other fertility secrets. Evolutionary psychologist Dr Geoffrey Miller and colleagues from the University of New Mexico studied the amount of money lap dancers earned at particular times of the month. He found that the women were asked to perform the largest number of dances, and therefore got the most money, during their most fertile days and so were most attractive to men then.