Medically reviewed by Dr. Bhimi Daimari, MBBS, MS (Obstetrics and Gynaecology) · Review date: 3 November 2026
If you are newly pregnant it is natural to count the weeks and wonder: “When is the risk of miscarriage highest and when can I stop worrying?” The good news is that the risk falls quickly as pregnancy moves forward especially once a heartbeat is seen on a scan. In this guide we explain miscarriage rates by week, how age changes the risk and what you can and cannot control.
Quick answer: About 10–20 in every 100 known pregnancies end in miscarriage and around 8 in 10 of these happen in the first 12 weeks. The risk is highest before 6–7 weeks. Once a normal heartbeat is seen on ultrasound, the risk drops sharply – to roughly 1–2% by 8–9 weeks – and it falls further after 12 weeks.
Miscarriage Rates by Week: The Big Picture
Many very early losses happen before a woman even knows she is pregnant (sometimes called a chemical pregnancy). Among pregnancies that are confirmed, most losses happen in the first trimester (ACOG). The table below gives a simple guide. Numbers are approximate and vary between studies and between women.
| Stage of pregnancy | Approximate risk of miscarriage | What it means |
|---|---|---|
| Weeks 3–5 (positive test, before a scan) | Highest | Many losses at this stage are chromosome problems and look like a late or heavy period. |
| Week 6 (heartbeat seen) | About 9 in 100 | Seeing a heartbeat is a very good sign. |
| Week 7 (heartbeat seen) | About 4 in 100 | Risk keeps falling every week. |
| Week 8 (heartbeat seen) | About 1–2 in 100 | Most pregnancies with a normal heartbeat now continue. |
| Week 9 onwards (heartbeat seen) | Less than 1 in 100 | Risk is low. |
| Weeks 13–20 (second trimester) | Uncommon (about 1–5 in 100) | Causes are often different (cervix, womb shape, infection). |
Heartbeat figures are based on a study of women without symptoms after a normal first-trimester scan (Tong et al., Obstetrics & Gynecology, 2008).
What Week Is the Highest Risk of Miscarriage?
The highest risk is in the first 6 weeks, before a heartbeat can be seen. This is when the most common cause – a chromosome problem that happens by chance – usually ends the pregnancy. Read more: what causes miscarriage.
Chances of Miscarriage at 8 Weeks and 9 Weeks
By 8 weeks, if a scan shows a normal heartbeat and the baby is the expected size, the chance of miscarriage is roughly 1–2 in 100. By 9 weeks it falls below 1 in 100. Bleeding or pain can still happen in a healthy pregnancy, but they should always be checked by a doctor.
Chance of Miscarriage at 12 Weeks After Seeing a Heartbeat
Once you reach 12 weeks with a normal scan, the risk is low – well under 1 in 100 in most studies. This is one reason many families wait until the 12-week scan to share their news.
Video: When Do Miscarriages Usually Occur?
In this short video, fertility specialist Dr. Randy Morris explains when most miscarriages happen and how the risk changes in early pregnancy.
Miscarriage Rates by Week and Age
Age has a big effect because egg quality changes over time. A large study from Norway found the risk was lowest for women aged 25–29 (about 10 in 100) and highest after 45 (over 50 in 100) (Magnus et al., BMJ 2019). The NHS gives these rough numbers:
- Under 30: about 1 in 10 pregnancies
- 30 to 39: about 2 in 10
- Over 45: more than 5 in 10
At every age, the risk still falls week by week once a heartbeat is seen.
What Women Ask on Reddit About Miscarriage Rates
Many women search Reddit for reassurance. In one popular discussion, a mum-to-be asked whether the miscarriage rate is really this low at 9 weeks. Shared stories can comfort you, but they are personal experiences, not medical advice. The study numbers above – and your own doctor – are the most reliable guide.
Is There a Miscarriage Risk Calculator After Heartbeat?
Online “miscarriage risk calculators” use averages from studies like the ones above. They can be reassuring, but they cannot know your personal situation, such as your health, scan results or symptoms. Use them for general information only, and ask your doctor about your own risk.
What Week Should I Stop Worrying About a Miscarriage?
There is no single “safe” day, but two milestones bring the most reassurance:
- Seeing a heartbeat (around 6–8 weeks): risk drops sharply.
- Reaching 12–13 weeks: the first trimester ends and the risk becomes low.
Worry is normal, especially after a previous loss. Talking to your doctor and going to your antenatal appointments can help.
What Habits Can Cause a Miscarriage?
Most early miscarriages are not caused by anything the mother did. But some habits do raise the risk:
- Smoking
- Drinking alcohol
- Using recreational drugs
- Very high caffeine intake (the NHS advises less than 200 mg a day)
- Uncontrolled diabetes or thyroid disease
Normal exercise, work, sex, light lifting and everyday stress do not cause miscarriage.
In early pregnancy, doctors may also check whether hCG is rising as expected. Read more in our guide to hCG levels by week.
Signs to Watch For and When to Get Help
Bleeding and cramps are the most common signs of miscarriage, but they can also happen in healthy pregnancies (threatened miscarriage). Some miscarriages have no symptoms and are found on a scan (missed miscarriage). To learn the signs, read what a miscarriage looks like.
Go to the emergency department or call 997 in Saudi Arabia if you have very heavy bleeding (soaking 2 large pads an hour for 2 hours), severe or one-sided pain, fever, or feel faint. For advice, call the Ministry of Health on 937.
Frequently Asked Questions
What is the most common week to miscarry in pregnancy?
Most miscarriages happen before 10 weeks and many happen before 6–7 weeks, often before a heartbeat can be seen.
What week is the highest risk of miscarriage?
The first 6 weeks carry the highest risk After a heartbeat is seen, the risk falls each week.
What are the chances of miscarriage at 8 weeks?
If a normal heartbeat is seen at 8 weeks, the chance of miscarriage is roughly 1–2 in 100.
What week should I stop worrying about a miscarriage?
Risk drops sharply after a heartbeat is seen and becomes low after 12–13 weeks. Your doctor can tell you what your scan means for you.
What habits can cause a miscarriage?
Smoking, alcohol, drugs and very high caffeine raise the risk. Normal exercise, work and everyday stress do not.
What causes miscarriage in early pregnancy?
The most common cause is a chromosome problem in the pregnancy that happens by chance. Read: what causes miscarriage.
Some early pregnancy losses have a less common cause, such as a molar pregnancy, which needs hCG follow-up after treatment.
Sources
- ACOG – Early Pregnancy Loss
- NHS – Miscarriage: Causes
- Magnus MC et al. Role of maternal age and pregnancy history in risk of miscarriage. BMJ 2019
- Tong S et al. Miscarriage risk for asymptomatic women after a normal first-trimester prenatal visit. Obstetrics & Gynecology 2008.
Medical disclaimer: This article is for general education only. It does not replace advice, diagnosis or treatment from a qualified doctor.