In-vitro fertilization is more effective for women under 35 who undergo six cycles of the treatment. The chances of birth in women under 35 are 86 percent. However, the chances are decreased to 50% in women over the age of 40.

A study was conducted on more than 6,000 women at a large Boston clinic to test the efficacy of IVF. It was found that the treatment was effective in infertile women younger than 35. It could give nearly the same chances of having a baby as in normal cases of women in the same age group.

But its efficacy in women above 40 was much less. The treatment could not counteract the decline in fertility that occurs in women above the age of 40. The study was one of its kind to assess how well IVF worked in women of different age groups.

Since the procedure is quite costly, costing about $12,000 per attempt, the patients had the right to know if it would be effective or not. Moreover the procedure can be physically and emotionally grueling as women have to undergo several weeks of hormone injections to stimulate the ovaries. Some of them even need a painful surgical procedure to remove the eggs, which are fertilized in the laboratory. When the hope turns to dejection, the women can face serious problems

"Even as effective as IVF is, it can't reverse the effects of aging," said Alan Penzias of Harvard Medical School, who led the study published in The New England Journal of Medicine. "We cannot reverse the biological clock."

Thus the study would guide women when to actually go in for IVF.