Miscarriage is far more common than most people realize. Roughly 10 to 25% of recognized pregnancies end in miscarriage, and a large WHO systematic review placed the overall rate at about 16%. That means if you or someone you know has experienced a pregnancy loss, it is one of the most common complications in reproductive health, not a rare event.
Overall Prevalence
The wide range of 10 to 25% exists because tracking miscarriage precisely is difficult. Many losses happen so early that a person may not even know they were pregnant. These very early losses, sometimes called chemical pregnancies, occur shortly after a fertilized egg implants and can easily be mistaken for a late or heavy period. Because of this, the true rate of pregnancy loss is almost certainly higher than what clinical records capture.
Among pregnancies that are confirmed through a test or medical visit, the best global estimate comes from a WHO review that analyzed data across multiple countries and populations. That review found a prevalence of 16.1%, meaning roughly one in six known pregnancies ends in miscarriage.
How Risk Changes Week by Week
Most miscarriages happen in the first trimester, and the risk drops sharply as the pregnancy progresses. A pooled analysis of over 12,000 pregnancies mapped the week-by-week decline:
- Weeks 5 through 8: Risk is at its highest, around 3 to 4% per week.
- Week 9: Risk drops to about 2%.
- Weeks 10 through 12: Risk falls to roughly 1% or less per week.
- Week 13 onward: Risk drops below 0.5% per week and continues to decline.
- Weeks 16 through 19: Risk is minimal, around 0.1% or lower.
This steep decline is why the end of the first trimester feels like such a milestone for many expecting parents. By week 13, the cumulative risk of loss has fallen dramatically from where it started.
The Heartbeat Milestone
Seeing cardiac activity on an ultrasound is one of the strongest reassurance points in early pregnancy. Research among women with a history of recurrent miscarriage found that reaching six weeks of pregnancy gave a 78% chance of the pregnancy continuing. Once a heartbeat was visible at eight weeks, that chance jumped to 98%. By ten weeks with a confirmed heartbeat, the probability of the pregnancy continuing rose to 99.4%.
These numbers come from a higher-risk group (women who had already experienced multiple losses), so for someone without that history, the odds after a confirmed heartbeat are likely even more favorable.
How Maternal Age Affects Risk
Age is the single biggest factor influencing miscarriage risk. A large register-based study published in The BMJ tracked hundreds of thousands of pregnancies and found a clear pattern:
- Under 20: 15.8% risk
- Ages 25 to 29: 9.8% risk (the lowest point, bottoming out at about 9.5% at age 27)
- Ages 35 to 39: Risk begins climbing noticeably
- Age 45 and over: 53.6% risk
The slightly elevated rate in teenagers compared to women in their late twenties likely reflects a mix of biological and social factors. The dramatic jump after 40 is driven largely by the increasing rate of chromosomal errors in eggs as they age. By 45, more than half of recognized pregnancies end in loss.
Why Most Miscarriages Happen
The majority of first-trimester miscarriages are caused by chromosomal abnormalities in the embryo. These are random errors that occur when the egg and sperm combine, resulting in an embryo with too many or too few chromosomes. The embryo simply cannot develop normally, and the pregnancy ends on its own. This type of loss is not caused by anything the pregnant person did or failed to do.
Other contributing factors include uterine structural issues, hormonal imbalances, blood clotting disorders, uncontrolled chronic conditions like diabetes or thyroid disease, and certain infections. But for a single, isolated miscarriage, chromosomal problems in the embryo are by far the most common explanation.
Recurrent Miscarriage
While a single miscarriage is common, experiencing two or more consecutive losses is much less so. Between 1 and 5% of women experience recurrent pregnancy loss. Having one miscarriage does not meaningfully increase your risk of having another. The odds of a successful pregnancy after a single loss remain high.
When losses do recur, doctors typically begin investigating potential underlying causes, such as uterine abnormalities, hormonal conditions, or immune-related factors. In many cases, even after two or three losses, the next pregnancy proceeds normally without any specific intervention.
What These Numbers Mean in Practice
Miscarriage is common enough that most people will either experience one personally or know someone who has. Yet it remains a topic many feel isolated by, partly because it often happens before a pregnancy has been shared publicly. Understanding how frequent pregnancy loss actually is can help put an individual experience in context: it does not signal that something is wrong with your body, and it does not predict what will happen in a future pregnancy.
The steep drop in risk after the first trimester, and especially after a heartbeat is confirmed, also means that the window of highest vulnerability is relatively narrow. For most people, once a pregnancy reaches 12 to 13 weeks with normal ultrasound findings, the likelihood of carrying to term is very high.