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- Research on week-by-week risk of miscarriage is limited, but we have early studies.
- According to one source, its about 25% at 4 weeks, 5% at 4-8 weeks, and 2% at 8-12 weeks.
- After the first trimester, your risk drops significantly and is somewhere between 0.5% to 3%.
The earlier your pregnancy is, the more likely you are to experience a miscarriage. About 80% of miscarriages take place in the first trimester, meaning the first 12 weeks of pregnancy, says Dr. Sandy Dorcelus, MD, an OB-GYN at NYU Langone Hospital.
But unfortunately, specific research around miscarriage rates by week is limited, in part because there's no reliable way of tracking early miscarriage other than self-reported data.
We've provided the best information based on available research, but if you're looking for your specific risks it's always best to speak with your doctor.
Miscarriage rates by week
As a pregnancy progresses the likelihood of miscarriage drops. However, sources disagree on just how quickly it drops and by how much.
According to the UK-based charity NCT, the rates of miscarriage are:
- 25% at 4 weeks gestation (the time of your missed period)
- 5% at 4-8 week gestation
- 1.7% at 8-12 weeks gestation
A 2013 study of more than 4,000 American women found these rates of miscarriage:
- ~14.5% at 6-9 weeks
- ~7% at 10-15 weeks
- Less than 2%: 16-19 weeks
After the first trimester, your risk of miscarriage drops rapidly:
- In weeks 13-20, your risk is about 2-3%.
- From weeks 20 until birth, pregnancy loss is called stillbirth, and the risk is about 0.5%.
If your doctor sees a healthy fetal heart rate at an early ultrasound — usually done between 7-8 weeks — it's a sign of healthy pregnancy and lower miscarriage risk.
On the other hand, having a low fetal heart rate at an early ultrasound is associated with increased miscarriage risk. However, you can still miscarry, even after seeing a heartbeat.
Miscarriage rates by age
Despite limited data about miscarriage rates by week, much more is known regarding maternal age and miscarriage.
Basically: "The risk of early pregnancy loss increases with age," Dorcelus says — in fact, age is one of the strongest predictors of miscarriage.
That's because the most common cause of miscarriage is fetal chromosomal abnormalities, or a fetus that develops in an abnormal way. And fetal chromosomal abnormalities are more common in fetuses conceived by older mothers.
A large 2019 study of over 400,000 Norwegian pregnancies found these miscarriage rates by age:
|
Maternal Age |
Miscarriage Risk (Approximate) |
|
Under 20 |
15.8% |
|
25-29 |
9.8% |
|
30-35 |
11-14% |
|
36-40 |
17-25% |
|
40-44 |
30-45% |
|
45 |
53.6% |
Other common causes of miscarriage
About half of miscarriages are caused by fetal chromosomal abnormalities. One example is a blighted ovum, which is when an embryo implants, but does not develop.
In addition to chromosomal abnormalities, miscarriages can be caused by:
- Problems with the uterus, including fibroids, a septate uterus or scar tissue in the uterus
- A cervical inefficiency, or short cervix
- Infection, including STIs
If you do have a miscarriage, it's important not to blame yourself as the cause.
"Miscarriages are unfortunately extremely common and are typically not the fault of the patient," says Dr. Kelli Burroughs, the department chairman of obstetrics and gynecology at Memorial Hermann Sugar Land Hospital.
Miscarriage risk factors
Certain factors can increase your risk for miscarriage, including:
- Being 35 or older
- Having two or more previous miscarriages
- Smoking, drinking alcohol and using drugs
- Being exposed to chemicals like paint thinner
- Autoimmune diseases like lupus
- A body mass index of 30 or higher
- Diabetes
- Thyroid disease
- Hormone-related conditions like polycystic ovary syndrome (PCOS)
- Prior surgery on your cervix which may have weakened it
In addition, some medical tests including amniocentesis and chorionic villus sampling increase miscarriage risk.
If you want to learn more about your individual miscarriage risk, especially if you have one of the conditions above, make an appointment with your OB-GYN.
Insider's takeaway
Many pregnant people want to learn more about miscarriage risk to set their minds at ease. Researchers do know some broad facts about miscarriage. Your risk of miscarriage decreases as your pregnancy progresses, and increases based on your age, especially if you're 35 or older.
However, miscarriage can happen to anyone, at any stage of pregnancy. Living a healthy lifestyle and seeking prenatal care early on can decrease your risk of miscarriage, but not eliminate it entirely.
Your week-by-week risk of miscarriage in early pregnancy, according to studies and gynos
Source: Kalayaan News
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