Most miscarriages can’t be prevented and aren’t caused by anything you did. Here’s what really affects the risk, the steps that help, and the truth about stress and caffeine.
The honest answer to how to prevent miscarriage is that most miscarriages can’t be prevented. More than half of early miscarriages happen because of a chance chromosome problem in the pregnancy, which nothing you do or don’t do can change. Most miscarriages are not caused by anything you did: not sex, exercise, work, lifting or ordinary stress. What you can do is lower the risks within your control, mostly before pregnancy: take folic acid, manage health conditions such as thyroid problems and diabetes, avoid smoking and alcohol, keep caffeine under 200 mg a day, and check that your medicines are safe. For women who have had a miscarriage before and then bleed in early pregnancy, progesterone may help.
What causes miscarriage
- Chromosome problems in the pregnancy, by far the most common cause. They happen by chance when egg and sperm combine, and become more common with age.
- Health conditions such as untreated thyroid disease, uncontrolled diabetes or certain blood-clotting conditions.
- Differences in the shape of the uterus, or large fibroids inside it.
- Some infections, smoking, alcohol, drugs and certain medicines.
About 8 in 10 miscarriages happen in the first 12 weeks.
What doesn’t cause miscarriage
Many women blame themselves for things that are safe in a normal pregnancy:
- sex
- exercise you were used to before pregnancy
- working, standing, or lifting everyday loads
- a minor fall or bump
- an argument, a bad day, or a stressful week
- flying, or eating spicy food
Can stress cause miscarriage?
Everyday stress has not been shown to cause miscarriage. Some studies have looked at very severe, long-lasting stress, but the results are mixed, and stress often comes with other factors such as poor sleep or smoking that make it hard to separate. If you’re anxious, that’s understandable, and support helps you feel better. But please don’t add guilt: a stressful time does not end a healthy pregnancy.
Can caffeine cause miscarriage?
Moderate caffeine, under 200 mg a day, doesn’t appear to raise the risk, according to the American College of Obstetricians and Gynecologists. That’s about one cup of brewed coffee, though strength varies a lot. Some studies link higher amounts with a higher risk, so it makes sense to stay under that limit when you’re pregnant or trying. Remember tea, soda, energy drinks and chocolate count too.
Steps that lower your risk
- Take folic acid, 400 micrograms a day, ideally starting before pregnancy.
- Manage health conditions before and during pregnancy, especially thyroid problems and diabetes.
- Don’t smoke, drink alcohol or use drugs.
- Keep caffeine under 200 mg a day.
- Check every medicine and supplement with your doctor or pharmacist, including herbal products.
- Aim for a healthy weight before pregnancy.
- Practice food safety: avoid unpasteurized cheese and milk, undercooked meat, and deli meats unless heated.
- Keep vaccinations up to date and avoid infections where you can.
How to prevent miscarriage with PCOS
Women with PCOS may have a somewhat higher miscarriage risk, likely linked to insulin resistance and weight. There’s no proven medicine to prevent miscarriage in PCOS. The most useful steps are getting blood sugar and weight into a healthy range before pregnancy and working with your doctor on any medicines you take. Our guide to getting pregnant with PCOS explains more.
Miscarriage risk by week of pregnancy
The risk is highest in the earliest weeks and falls as pregnancy goes on. It drops noticeably once a heartbeat is seen on ultrasound, and again after the first 12 weeks. Miscarriage after the first trimester is uncommon.
After two or more miscarriages
Most women who have one miscarriage go on to have a healthy pregnancy. After two or more, ask your doctor about testing for causes, such as blood-clotting problems, thyroid disease, the shape of the uterus, and chromosomes in both partners. Some of these can be treated. In UK guidance, women who have had a miscarriage before and then have bleeding in early pregnancy are offered progesterone, a pregnancy-supporting hormone given as a vaginal pessary, which in a large trial modestly increased live births in this group. It didn’t help women without a previous miscarriage.
When to get urgent care
- heavy bleeding, soaking a pad every hour for two hours or more
- severe pain, especially on one side, or shoulder-tip pain
- fever, chills or foul-smelling discharge
- dizziness or fainting
Light spotting is common in healthy pregnancies, but call your doctor or midwife about any bleeding so they can check.
It’s not your fault
If you’ve had a miscarriage, please hear this: it almost certainly wasn’t caused by something you did or didn’t do. Grief, guilt and fear are all normal, and you don’t have to carry them alone. Our guides to a missed miscarriage, your first period after a miscarriage and getting pregnant after miscarriage may help with what comes next.
Reviewed October 2026. Author: Qingcai Wang, MD, PhD, founder of Five Essences. General education only; continue your medical care.
Sources: ACOG: early pregnancy loss; ACOG Committee Opinion 462: moderate caffeine consumption during pregnancy; Coomarasamy et al., PRISM trial of progesterone (2019), and NICE guideline NG126.