article_snippet: the womb is known that for most women, there is a two to four day time period when the lining gives out the key chemical signals that allow the embryo to attach, leading to a pregnancy.
article_snippet: But a team of scientists, led by Professor Juan Garcia Velasco at the IVI fertility clinic in MadridMadrid, said a team of scientists, led by Professor Juan Garcia Velasco at the IVI fertility clinic in Madrid believe failed attempts often happen because an embryo is implanted at the wrong time, missing a woman's crucial window of fertility.
article_snippet: Until now, the endometrium was kind of a black box.
article_snippet: But after the test was used to determine each woman's window of implantation, nine of the 17 became pregnant and went on to have a baby.
article_snippet: It has previously been assumed that the window of implantation was 'constant in all women,' the researchers note.
article_snippet: As a result, two embyros were implanted at the key seven-day point, after progesterone replacement, and the woman became pregnant with twins.
article_snippet: The pregnancy was uneventful and twins boys were delivered by Caesarean section at 36 weeks.
article_snippet: Each had suffered between one and six implantation failures.
article_snippet: Of the women taking part nine became pregnant and gave birth.
article_snippet: Yet after performing the test, The researchers discovered all previous implantation attempts had been two days premature.