The Lancet work involved 253 couples with unexplained infertility who had been trying for a baby for over a year.
Unexplained fertility problems - where no obvious abnormalities can be found - account for about 40% of female infertility and 8-28% of infertility in couples.
Data suggests that there is a 33-60% chance that such couples will conceive naturally over three years.
The latest study, by the Academic Medical Centre in Amsterdam, focused on couples with unexplained fertility problems who were estimated to have a 30-40% chance of conceiving spontaneously within 12 months.
The estimations were based on the woman's age, how long the couple had been experiencing subfertility and the results of lab tests, including sperm analysis.
Half were randomly assigned to the fertility treatment for six months and the other half were asked to carry on trying to conceive naturally for six months.
The fertility treatment, intrauterine insemination (IUI) with controlled ovarian hyperstimulation, involved using drugs to make the woman's ovaries produce eggs and inserting her partner's sperm directly into her womb.
With the fertility treatment, 42 (33%) women conceived and 29 (23%) had ongoing pregnancies. Similarly, in the group that carried on trying to conceive naturally, 40 (32%) women conceived and 34 (27%) had ongoing pregnancies.
Therefore, in terms of successful pregnancies, the fertility treatment added no benefit.
IUI with controlled ovarian hyperstimulation increases the chance of multiple pregnancies and these are associated with higher risks for both the mother and the infants and considerable psychological and financial strain for some couples.
Rarely, stimulating the ovary can lead to a life-threatening condition called Ovarian Hyperstimulation Syndrome.
Dr Richard Kennedy, gynaecologist and spokesman for the British Fertility Society, said: "It's further evidence to confirm what we know.
"It provides some reassurance to couples experiencing difficulties that the 'do nothing' option can produce results. We should be giving this advice to patients."
But he said it did create a conundrum for doctors.
"You are faced with a couple who are desperate to have a baby and they come along to see a fertility specialist with great expectations and hopes and then they are told to go away and do nothing for six months. That is quite a hard pill to swallow."
He said that a decision should be reached jointly between the couple and their doctor, weighing up the benefits and the risks of intervening and doing nothing, and that each case would be different.
"What you might say to a 28-year-old woman who has been trying for a baby for 18 months and has had a baby before would be entirely different from what you might say to a 38-year-old woman who has been trying for 18 months and has never been pregnant."
The National Institute for Clinical Excellence suggests IUI treatment after three years of unexplained infertility.
It also recommends that people who are concerned about their fertility should be informed that sexual intercourse every two to three days optimises the chance of pregnancy.
Fertility Facts
 About 84% of couples conceive within a year with regular intercourse and no contraception.
Of those who do not conceive in the first year, about half will do so in the second year.
Female fertility declines with age
July 2006 |
