Hearing your baby’s heartbeat for the first time is an exciting milestone — and not just because it’s proof of a future life, but because your miscarriage risk actually declines. According to a study published in JAMA, after an ultrasound confirms a baby's heartbeat at 8 weeks, the risk of miscarriage is ~3%.
All in all, most healthcare providers will say the first 13 weeks of pregnancy are the most critical (1st trimester) since rapid growth and development take place during this time. The embryo-turned-fetus develops distinct facial features, limbs, organs, bones, and muscles, and has an assigned sex!
Getting past your first trimester without any complications reduces your risk of miscarriage even further. Still, pregnancy — especially after a long and difficult fertility journey — is not without anxiety, so to help ease your worries, let’s dive into what the chances actually are of having a miscarriage after hearing a heartbeat.
What is the chance of miscarriage in general?
For generally healthy women in the United States, the miscarriage risk is between 10-25%, according to the American Pregnancy Association. Not surprisingly, as you age, your risk of miscarriage increases to 20-35% by the time you’re 35 and 50% by the time you’re 45.
Most miscarriages (80%) take place during the first trimester (weeks 0-13), 1-5% take place after the 13-week mark, and any miscarriage that happens after 20 weeks is considered stillbirth.
What are some miscarriage risk factors?
Factors that can put women at risk of miscarriage (according to the National Health Service) in their first trimester include:
Placenta development problems
Chromosomal issues (eg, the fetus produces too much or too little DNA material, which can be due to the embryo itself, genetic issues from either parent, or both)
Factors that can put women at risk of miscarriage (according to the National Health Service) in their second trimester include:
Medical conditions such as polycystic ovary syndrome (PCOS), diabetes, thyroid disorders, autoimmune diseases, and clotting disorders
Infections such as chlamydia, gonorrhea, syphilis, and bacterial vaginosis
Certain medications like misoprostol for stomach ulcers and methotrexate for inflammatory conditions like rheumatoid arthritis (always check with your doctor when taking medications during pregnancy)
Abnormal womb structure
Excessive drug, alcohol, and/or caffeine use
Being under or overweight
The different types of miscarriage and their likelihood
1. Chemical pregnancy
A chemical pregnancy is an early miscarriage that happens shortly after implantation and often before a woman even realizes she’s pregnant. The egg gets fertilized and cues the body to produce the pregnancy hormone HCG, but the fertilized egg never implants itself into the uterus.
Chemical pregnancies represent somewhere between 8-33% of all pregnancies and 18-22% of IVF pregnancies.
2. Ectopic pregnancy
An ectopic pregnancy happens when a fertilized egg implants and grows outside the main cavity of the uterus, typically in the fallopian tube. In rare cases, it can occur in other locations such as the cervix, ovary, or abdomen, but the majority of ectopic pregnancies take place in the fallopian tube.
Ectopic pregnancies are usually detected in a woman’s first 8 weeks and account for up to 2% of all pregnancies.
3. Clinical miscarriage
A clinical miscarriage is similar to a chemical pregnancy where there are initial signs of pregnancy, but with additional clinical indicators on top of a positive pregnancy test, such as a missed period or visible fetal sac during an ultrasound.
It’s unsure how common these are, but the likelihood is somewhat similar to the percentage of people affected by chemical pregnancies.
4. Missed miscarriage
A missed miscarriage, also known as a silent miscarriage, occurs when the fetus has stopped developing, but the body hasn’t expelled it yet or shown clear signs of miscarriage.
You won't experience common miscarriage symptoms, like cramping or bleeding. Instead, you'll find out you've had a miscarriage once you lie down for an ultrasound and there's no fetal heartbeat.
Missed miscarriages occur in about 8-20% of clinically confirmed intrauterine (ie, implanted in the uterus) pregnancies.
A missed miscarriage typically happens during the first trimester though it can occur at any time during a pregnancy.
5. Blighted ovum
A blighted ovum, also called an anembryonic pregnancy, occurs when a fertilized egg implants in the uterus, but the embryo doesn’t develop or isn’t visible on an ultrasound. A gestational sac forms, but without an accompanying embryo. The early-stage embryo gets reabsorbed and leaves the empty gestational sac behind.
A blighted ovum typically happens in the first trimester and is usually discovered between weeks 8 and 13.
6. Molar pregnancy
A molar pregnancy is when an egg and sperm join incorrectly at fertilization and create a noncancerous tumor, which prevents the healthy growth of a normal placenta. The tumor can’t support a developing embryo and the pregnancy ends.
Molar pregnancies are a type of gestational trophoblastic disease (GTD), a rare group of conditions that causes tumors to develop inside the uterus from tissue that forms shortly after conception.
Molar pregnancies are very rare, affecting less than 1% of all pregnancies (roughly 1 in every 1,000), and are typically found during the first trimester since they can be detected via ultrasound.
7. Recurrent miscarriage
A recurrent miscarriage, also known as recurrent pregnancy loss, is when you have 2 or more consecutive pregnancy losses before your 20th-week mark.
Recurrent miscarriages are very rare, only affecting around 1-2% of couples and fairly misunderstood to this day. Over 50% of all recurrent miscarriage cases lack a clear etiology (ie, cause).
When there is a known cause, it's typically linked back to genetics (chromosomal abnormalities of the embryo or the parents), endocrine issues, autoimmune conditions, environmental and lifestyle factors, uterine abnormalities, and blood clotting disorders such as antiphospholipid antibody syndrome.
8. Threatened miscarriage
A threatened miscarriage is when there’s vaginal bleeding during the first 20 weeks of pregnancy, indicating the potential for pregnancy loss.
According to the National Health Service, bleeding during your pregnancy does not automatically mean you’ll go on to miscarry. There’s actually an 83% chance of your pregnancy continuing.
Bleeding during pregnancy can be due to a vaginal infection, a small blood clot around the amniotic sac, damage to the cervix, and changes in the position of the placenta as it buries itself into the lining of the womb.
Threatened pregnancies are the most common pregnancy complication, occurring in roughly 15-20%.
9. Inevitable miscarriage
An inevitable miscarriage is when a woman has unexplained, heavy vaginal bleeding and intense abdominal pain in her first 20 weeks of pregnancy.
Compared to a threatened miscarriage, an inevitable miscarriage is where the cervix opens in addition to bleeding and pain, which is a sign the body’s in the process of miscarrying. It’s referred to as “inevitable” because the symptoms can’t be stopped and a miscarriage will occur no matter what.
10. Vanishing twin miscarriage
A vanishing twin miscarriage, also known as vanishing twin syndrome, is when a twin or multiple disappears in the uterus during pregnancy due to one or multiple embryos dying. The fetal tissue gets reabsorbed by the other embyro(s), placenta, or the mother.
A vanishing twin miscarriage is typically observed sometime between the 7th and 12th weeks of pregnancy, and generally, during the first trimester.
Vanishing twin miscarriages are estimated to take place in around 36% of twin pregnancies and in 50% of pregnancies that begin with 3+ gestational sacs.
While miscarriages are common — according to the American College of Obstetricians and Gynecologists (ACOG), as many as 26% of all pregnancies and 10% of clinically recognized pregnancies end in miscarriage — the risk of miscarriage drastically lowers to ~3 after a heartbeat is confirmed, and even more the further along in pregnancy you are. However, if you do find yourself on the wrong side of the statistics, it’s important to keep in mind that your miscarriage is not your fault. Most miscarriages occur due to chromosomal abnormalities of the embryo or other factors outside of your control, so try to give yourself grace during this time. Remember, we’re here to support you every step of the way.
Caroline McMorrow is a Content Strategist at Rescripted.