Miscarriage Risk by Week: What the Data Says

As an OB-GYN, one of the questions I hear most often in early pregnancy is: “What are my chances of miscarriage this week?” The anxiety is real and completely understandable. Having clear, evidence-based data can help — both to manage fear and to know when to seek help. For the full picture of what happens during these early weeks, see our first trimester guide. This article presents the statistics as honestly as possible, because knowledge is empowering.

📌 Key Takeaway: The overall miscarriage rate for known pregnancies is 10–20%, with the vast majority occurring before week 12. Once a heartbeat is confirmed on ultrasound (around week 7–8), the risk drops to approximately 3–5%. By week 12, it falls below 1%. Most miscarriages are caused by chromosomal abnormalities and cannot be prevented.

Miscarriage Risk by Week

The following data is compiled from multiple peer-reviewed studies, including research published in Obstetrics & Gynecology, the British Medical Journal, and Fertility and Sterility.

📊 Key Data: A landmark 2008 study in Obstetrics & Gynecology analyzed over 697 pregnancies with confirmed heartbeats and found the miscarriage rate was 9.4% at 6 weeks, 4.2% at 7 weeks, 1.5% at 8 weeks, and 0.5% at 9 weeks. These numbers are among the most cited in the medical literature.

What the Numbers Mean

If you’re reading this at week 6 and feeling anxious, here’s the encouraging perspective: even at the highest-risk period, the odds are overwhelmingly in your favor. At week 6, there’s an 85–92% chance your pregnancy will continue normally. By week 8 with a confirmed heartbeat, it’s 95–97%.

Track your exact week with our Week-by-Week Tracker.

Risk Factors That Affect Your Personal Risk

While the overall statistics apply to the general population, certain factors increase or decrease individual risk:

Factors That Increase Risk

Factors That Are NOT Risk Factors

It’s important to dispel common myths. The following do NOT cause miscarriage:

• ❌ Exercise (moderate exercise is safe and recommended by ACOG)
• ❌ Stress (normal daily stress does not cause miscarriage)
• ❌ Lifting objects (within normal daily limits)
• ❌ Having sex
• ❌ Eating spicy food
• ❌ Working at a computer
• ❌ Flying on an airplane
• ❌ Emotional upset or arguments
• ❌ Previous use of birth control pills

⚠️ Important: If you’ve experienced a miscarriage, it was almost certainly NOT caused by anything you did or didn’t do. About 50–60% of first-trimester miscarriages are caused by chromosomal abnormalities — random errors during cell division that cannot be predicted or prevented.

Warning Signs to Watch For

Contact your healthcare provider immediately if you experience:

• Heavy vaginal bleeding — soaking a pad in an hour or passing clots
• Severe abdominal cramping — especially if one-sided (could indicate ectopic pregnancy)
• Passage of tissue from the vagina
• Sudden disappearance of pregnancy symptoms (not always a warning — symptoms naturally fluctuate)
• Fever above 100.4°F (38°C) with bleeding

💡 Tip: Light spotting in the first trimester is common and does NOT necessarily indicate miscarriage. About 25% of women experience some bleeding in early pregnancy, and more than half of them go on to have healthy pregnancies. However, always report any bleeding to your provider for evaluation.

What Causes Miscarriage

When to Feel Reassured

These are genuine milestones that significantly reduce miscarriage risk:

• ✅ Positive pregnancy test: You’re pregnant — this is real
• ✅ hCG levels rising normally: Doubling every 48–72 hours in early pregnancy
• ✅ Gestational sac seen on ultrasound (week 5): Pregnancy is in the uterus
• ✅ Heartbeat detected (weeks 6–7): Risk drops to 5–10%
• ✅ Strong heartbeat at week 8: Risk drops to 3–5%
• ✅ Passed week 12: Risk is below 1%
• ✅ Normal NT scan / NIPT results: Chromosomal conditions screened

For the full list of tasks and milestones in early pregnancy, see our first trimester checklist and schedule your first prenatal appointment.

FAQ

Does seeing a heartbeat guarantee the pregnancy is safe?

Seeing a heartbeat is very reassuring — it reduces miscarriage risk to 3–5% at week 8 and below 1% by week 12. However, it doesn’t eliminate all risk. A small percentage of pregnancies with an early heartbeat still result in loss. The heartbeat milestone is the single strongest predictor of a viable pregnancy.

Should I avoid telling people I’m pregnant before 12 weeks?

This is a personal choice. The tradition of waiting until 12 weeks is based on the higher miscarriage risk in the first trimester. Some couples prefer privacy; others find it helpful to have support early, especially if complications occur. There’s no medical reason to wait — tell people whenever you feel comfortable.

How many miscarriages are “too many”?

ACOG recommends evaluation for recurrent pregnancy loss after 2 or more consecutive miscarriages. Testing may include genetic testing of both parents (karyotype), uterine imaging (ultrasound or HSG), hormone tests, and blood clotting disorder screening. About 60% of couples with recurrent loss go on to have a successful pregnancy.

Can progesterone supplements prevent miscarriage?

For women with a history of recurrent miscarriage, progesterone supplementation in early pregnancy may reduce the risk. A 2019 study in the New England Journal of Medicine (PRISM trial) found that vaginal progesterone improved live birth rates in women with a history of 3+ miscarriages. However, routine progesterone for all pregnant women is not recommended. Discuss with your provider if you have risk factors.

A Note on Healing

If you’ve experienced a miscarriage, I want you to know: grief is valid, and healing takes time. Loss at any stage of pregnancy is real loss. Resources like the March of Dimes Bereavement Program, SHARE Pregnancy & Infant Loss Support, and your healthcare provider’s counseling referrals can provide compassionate support.

You are not alone, and your experience matters.

References

• American College of Obstetricians and Gynecologists. “Early Pregnancy Loss.” acog.org
• Tong, S. et al. (2008). “Miscarriage Risk for Asymptomatic Women After a Normal First-Trimester Prenatal Visit.” Obstetrics & Gynecology. journals.lww.com
• March of Dimes. “Miscarriage.” marchofdimes.org
• Coomarasamy, A. et al. (2019). “Progesterone to Prevent Miscarriage in Women with Early Pregnancy Bleeding (PRISM).” New England Journal of Medicine. nejm.org
• Mayo Clinic. “Miscarriage — Symptoms and Causes.” mayoclinic.org

Written by

Dr. Rachel Nguyen

Board-Certified OB-GYN, Medical Reviewer

Dr. Nguyen is a board-certified OB-GYN with 15 years of experience in maternal-fetal medicine. She serves as medical reviewer for Pregnancy Guide, ensuring all content reflects current clinical evidence and ACOG best practices.