Just the Facts: The Chances of Having a Miscarriage Week-By-Week
If you're newly pregnant, you may already know that your chance of miscarriage decreases by every week of pregnancy, but what are the chances of miscarriage week-by-week?
Overall, the chance of miscarriage drops dramatically past the first trimester, or beyond 12 weeks of pregnancy. This is traditionally why so many women and couples have often waited to formally announce pregnancies until after the first trimester. (Of course, we know now that it's perfectly fine and acceptable to announce a pregnancy whenever you want to, so this is not an unspoken rule anymore!)
You should know, however, that every pregnancy is different. Overall, about 15% of pregnancies end in miscarriage, which is defined as a loss before 20 weeks of pregnancy.
The exception to that “rule,” of course if you have a history of recurrent miscarriage or a health condition that puts you at a higher risk of a miscarriage. There are also different rates of miscarriage based on your age and mode of conception; for example, as women age, the risk of miscarriage increases. In those cases, there may be a higher risk than an average pregnancy in a woman without a health condition.
If you're wondering what your chances of miscarriage week-by-week are during your pregnancy, here's what you need to know. First of all, you should know the different factors that increase the risk of miscarriage in general, which include:
- Age. After the age of 35, a woman's risk of miscarriage jumps up to around 20 percent. Over the age of 4o, that risk increases to 40 percent.
- Health status. This includes weight, if you're a smoker, and if you have any medical conditions, such as diabetes.
- History of loss. If you've had more than three reoccurring miscarriages in the past, you may have a higher risk of miscarrying and may need further testing. This does not apply if you've had term pregnancies between losses, however.
- Mutiples. The risk of miscarriage is higher in pregnancies with more than one fetus.
Miscarriage Week-By-Week Risk
Aside from overall risks, what are the risks by week during your pregnancy? Here is a chance of miscarriage week-by-week breakdown:
Your highest risk of miscarriage occurs in the first seven weeks of pregnancy. Most women find out they are pregnant at 4 weeks, so that leaves three weeks of anxious wondering. However, 80% of all miscarriages occur in the first trimester of pregnancy, which lasts until 12 weeks.
One study of pregnant women in Austria found that the risk of miscarriage after 10 weeks (most women hear their baby's heartbeat sometime after week 10) dropped significantly, to a less than under 1 percent risk. Women at 7 weeks of pregnancy had just over a 4% risk of miscarriage and then in just a single week, at week 8, that risk dropped to only 1.5 percent.
Another study found that the rate of miscarriage between 10 and 13 weeks of pregnancy was 2.8 percent, although many of those were “missed” miscarriages, meaning that the woman had unfortunately not known that her pregnancy had already ended.
Miscarriage risks in the second trimesters are low, but they are also hard to predict because unlike first trimester losses, which are most often caused by a chromosomal abnormality in the developing embryo, second-trimester losses are caused more by other factors. They may be due to undetected health condition in either the mom or the baby, for example, so it's hard for researchers to accurately predict the risk of a miscarriage during these weeks. It can also be hard to get accurate rates on risks because a woman may discover a loss in the second trimester when the loss actually occurred in the first. Later losses are even more rare and past 20 weeks, a loss is considered a stillbirth, not a miscarriage. One study noted that between 1 and 5 percent of pregnancies end between 13 and 19 weeks of pregnancy and 0.3 percent of pregnancies at 20 to 27 weeks' gestation, which is also the rate of third-trimester stillbirths.
It can be very difficult to try to move through a pregnancy without knowing your true risk of miscarriage. But please know that the risk, in general, does decrease with every week of pregnancy. If you're experiencing anxiety concerning your pregnancy or your risk of a loss to the point that it is interfering with your activities of daily functioning, please seek help from your doctor or another trained mental health professional.