10-20% of known pregnancies end in miscarriage. Most happen in the first trimester, and the risk drops significantly after certain milestones.
Common Causes
- Chromosomal abnormalities (most common — usually random, not inherited)
- Blood-clotting problems
- Abnormalities of uterus or cervix
- Hormone imbalances
- Immune responses that disrupt implantation
Most first-trimester miscarriages are due to chromosomal issues and are not preventable. They don't indicate future fertility problems.
Risk Reduction After Key Milestones
- After detecting fetal heartbeat: ~4% risk
- At 8 weeks with heartbeat: 1.5% risk
- After 14 weeks (second trimester): less than 1% risk
Once you see a heartbeat on ultrasound, the chance of miscarriage drops significantly.
Many people wait until after the first ultrasound before sharing the news with close friends and family, and second trimester before sharing more widely. Consider who you would want support from, and who you might feel uncomfortable sharing with, if you had a loss.
Bleeding in Early Pregnancy
25% of pregnant women have some bleeding or spotting in the first trimester.
Light spotting:
- Doesn't necessarily increase miscarriage risk
- Can be normal, especially around the time of implantation or after sex
Heavy bleeding:
- Similar to or heavier than a period
- More concerning — call your provider right away
If You Have Multiple Miscarriages
The risk of having 2 miscarriages in a row is less than 2%. If you've had 2+ consecutive miscarriages, your provider may recommend testing for underlying causes:
- Blood clotting disorders (thrombophilias)
- Uterine abnormalities (septum, fibroids)
- Hormone issues (thyroid, progesterone)
- Chromosomal issues in either partner (rare)
Testing can identify treatable causes, and most people go on to have successful pregnancies even after multiple losses.
When to call your provider:
- Heavy bleeding (soaking through a pad per hour)
- Severe cramping or pain
- Passing tissue
- Fever or chills (signs of infection)