Super-fertility may be a significant factor behind recurrent miscarriages in some women, according to experts.
They explained wombs of some women are too good at letting embryos implant, even those of poor quality, which should be rejected.
When poorer embryos are allowed to implant, the resulting pregnancies would then fail.
One expert welcomed the findings, published in the journal PLoS ONE, and hoped a test could be developed for identifying the condition in women.
Doctors at Princess Anne Hospital in Southampton and the University Medical Center Utrecht, took samples from the wombs of six women who had normal fertility and six who had had recurrent miscarriages.
High or low-quality embryos were placed in a channel created between two strips of the womb cells.
Cells from women with normal fertility started to grow and reach out towards the high-quality embryos. Poor-quality embryos were ignored.
However, the cells of women who had recurrent miscarriages started to grow towards both kinds of embryo.
"Many affected women feel guilty that they are simply rejecting their pregnancy. But we have discovered it may not be because they cannot carry, [but] it is because they may simply be super-fertile, as they allow embryos which would normally not survive to implant," the BBC quoted said Prof Nick Macklon, a consultant at the Princess Anne Hospital, as saying.
"When poorer embryos are allowed to implant, they may last long enough in cases of recurrent miscarriage to give a positive pregnancy test," he added.
But they noted that this theory still needs further testing and will not explain all miscarriages.