A team of doctors claim that “super-fertility” may explain why some women have multiple miscarriages.
They say the wombs of some women are too good at letting embryos implant, even those of poor quality which should be rejected.
The UK-Dutch study published in the journal PLoS ONE said the resulting pregnancies would then fail.
One expert welcomed the findings and hoped a test could be developed for identifying the condition in women.
Recurrent miscarriages – losing three or more pregnancies in a row – affect one in 100 women in the UK.
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.
Prof. Nick Macklon, a consultant at the Princess Anne Hospital, said: “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.”
He added: “When poorer embryos are allowed to implant, they may last long enough in cases of recurrent miscarriage to give a positive pregnancy test.”
This theory still needs further testing and will not explain all miscarriages.