Chances & risks of recurrent pregnancy loss
What are the chances of having more than one miscarriage?
While pregnancy loss usually is a one-time occurrence, up to one in twenty couples experience two miscarriages in a row, and one in one hundred have three or more. In some cases, these couples have an underlying problem that is causing the losses.
After an isolated spontaneous miscarriage, the chance of having a successful pregnancy in the future is quite high. Every time you get pregnant, you have the same age-based risk of pregnancy loss. Based on chance alone, the odds of having 2 miscarriages in a row are:
[age-based chance] X [age-based chance]
In other words, a 32-year-old woman who has a 15% chance of miscarrying in her first pregnancy will have a 15% of 15%, or a 2.25% chance of having a second consecutive miscarriage, based on chance alone.
In reality, however, the chance of consecutive miscarriages is higher than one would expect based on chance alone. That is because there are real and persistent causes of pregnancy loss that add to the chance of having a miscarriage.
Two researchers have investigated what the risk of miscarrying again is after 1, 2 or 3 miscarriages. Dorothy Warburton studied women who’d had at least 1 baby in 1964 and again in 1979. Malcolm Macnaughton studied women who had no previous babies and published his results in 1964.
Warburton and Macnaughton's results are set our in the table below:
|Chance of next
|according to Warburton
(if you've previously had a baby)
|according to Macnaughton
(if no previous baby)
|after 1 previous
|after 2 previous
|after 3 previous
Since Warburton and MacNaughton, much has changed in our understanding of the causes of recurrent pregnancy loss. We now have the ability to identify a problem in approximately half of the couples we investigate. If no cause can be found, the chance of the next pregnancy going to term is usually not all that different to a woman’s age-related chance of success.
In 1999, a group of researchers at Liverpool Hospital in the UK, one of the largest miscarriage clinics in the world, examined the histories of more than 700 of their patients in whom no cause of recurrent miscarriage could be found.
As you can see in their results in the table below, even when a couple have experienced several miscarriages, there is a very high probability that their next pregnancy will go to term:
Chance of next pregnancy going to term based on age and miscarriage history:
|Number of previous miscarriages
Brigham et al . Human Reproduction 1999