- 37% of repeat miscarriages have no known cause
- Women struggling to conceive after loss may benefit
- Still early — no new treatments yet
This finding helps explain why so many women suffer repeated pregnancy loss without answers.
It’s 2 a.m. Sarah is awake again, staring at the ceiling. She’s had three miscarriages in two years. Each time, the doctor said, “We don’t know why.” She feels broken. She’s not alone.
Millions of women like Sarah face recurrent pregnancy loss (RPL). It’s defined as two or more miscarriages in a row. Experts once thought it was rare. But new research shows it may affect up to 1 in 100 women — and for most, doctors can’t find a reason.
That lack of answers takes a toll. Many feel isolated. Some blame themselves. Treatments exist, but they don’t work for everyone. And because causes vary, care often feels like guesswork.
Right now, many women go months — even years — without a clear diagnosis. Testing differs from clinic to clinic. Some doctors check for hormone issues. Others look for blood clotting disorders. But there’s no standard checklist.
This leaves gaps. And confusion. Patients wonder: Did I do something wrong? Could this happen again?
Until now, we didn’t have a clear picture of how common RPL really is — or what’s behind it.
The surprising shift
For years, doctors assumed most repeat miscarriages were due to hormone problems or uterine shape. Some believed blood clots were the main culprit.
But here’s the twist: the largest review of its kind shows nearly four in ten cases have no known cause.
That’s more than any single medical factor.
What’s different this time? Researchers analyzed 105 studies — more than 47,000 women — to get the clearest snapshot yet.
What scientists didn’t expect
They expected to find a dominant cause. Instead, they found mystery.
The top known cause? Acquired thrombophilia — a tendency to form blood clots — found in 12% of cases.
Next: hormone imbalances (8%), uterine issues (6%), and inherited clotting disorders (6%).
But the biggest category by far? Unexplained.
This doesn’t mean this treatment is available yet.
Think of the body like a garden. For a seed to grow, you need good soil, water, and sunlight. Pregnancy is similar. Even if the embryo is healthy, problems in the environment — like blood flow or immune signals — can stop it from taking root.
Some researchers now believe RPL may be less about one broken part — and more about a system out of balance.
Like a traffic light stuck on red, something may be blocking the signals the body needs to sustain pregnancy.
One in three women get no answers
Among women with recurrent loss, 37% had no identifiable cause after full testing. That’s more than a third.
Compare that to 12% with clotting issues. Or 8% with thyroid or hormone problems.
Even when doctors find a cause, treatment isn’t always clear. But when there’s no cause, it’s harder to know what to do.
But there’s a catch.
This isn’t a study of all women. It’s a summary of past studies — mostly from fertility clinics.
So the data reflect women who sought help, not every woman who’s had repeat miscarriages.
Also, only two studies looked at RPL in the general population. That means we still don’t know exactly how common it is worldwide.
The hidden variation
Where you live affects what doctors test for — and what they find.
In some regions, hormone issues are more commonly diagnosed. In others, clotting disorders top the list.
This suggests testing practices — not just biology — shape the results.
And that’s a problem. Without standard rules, one woman might get five tests. Another might get two.
If you’ve had more than one miscarriage, you’re not alone. And not to blame.
This study doesn’t offer a new treatment. But it does validate a painful truth: many women suffer without answers.
Right now, there’s no new pill or test to ask for. But this research may push clinics to adopt clearer, more consistent testing.
Talk to your doctor about a full evaluation if you’ve had two or more losses. Ask what tests they recommend — and why.
Researchers say we need global standards for diagnosing RPL. That means the same definition, the same tests, the same reporting.
Until then, progress will be slow. But this study lays the groundwork.
More studies are needed — especially in diverse populations. Scientists are exploring immune markers, genetic factors, and microbiome links.
But big changes take time. For now, awareness is the first step.
