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when are miscarriages most common

Miscarriages are most common in the first trimester , especially in the very early weeks (around weeks 5–10 of pregnancy).

Key timing at a glance

  • Around 10–20% of known pregnancies end in miscarriage, and about 80% of these happen in the first trimester (up to 12–13 weeks).
  • The highest risk is in the earliest weeks (roughly weeks 0–6), when some losses look like a slightly late or heavy period and may never be recognized as a pregnancy.
  • Most clinically recognized miscarriages cluster between 6 and 8 weeks of gestation.
  • After a heartbeat is seen around 6–7 weeks, the risk drops significantly (down to around 10% and then continues falling with each week).
  • By the end of the first trimester (around 12–14 weeks), the chance of miscarriage is much lower; in the second trimester, estimated loss rates are roughly 1–5% (often quoted around 2–3%).

Simple week-by-week pattern (approximate)

This isn’t a precise personal risk calculator, but it reflects the general pattern clinicians and large health organizations describe.

  • Before 6 weeks
    • Biochemical or “chemical” pregnancies are common; loss may appear as a slightly late period.
* Risk is at its highest here, but many pregnancies aren’t yet confirmed.
  • 6–8 weeks
    • This is when many diagnosed miscarriages occur.
* A lot of these are due to chromosomal abnormalities in the embryo, not something a parent did.
  • 8–12 weeks
    • Risk continues but steadily drops each week, especially once a heartbeat has been confirmed.
* By around 10–12 weeks, the chance of an ongoing pregnancy continuing is high.
  • After 12–14 weeks
    • More than 80% of miscarriages have already happened by this point.
* Second-trimester losses are relatively uncommon, estimated in the low single-digit percentages (around 1–5%).

* After around 20 weeks, losses are rare and often classified differently (stillbirth rather than miscarriage).

Why they’re most common early

  • Many early miscarriages happen because of chromosomal abnormalities in the embryo, which prevent normal development.
  • The body often ends these pregnancies naturally very early, before or shortly after the first missed period.
  • This is usually not caused by exercise, sex, minor falls, or everyday stress, even though many people fear those things.

A quick example: someone who just got a positive test at 4–5 weeks is statistically in the highest-risk window, but if they reach 10–12 weeks with a normal scan and heartbeat, their chances of continuing pregnancy become much better.

If you’re pregnant and worried

  • Contact a healthcare provider urgently if you have heavy bleeding, strong cramps, or passing clots or tissue.
  • Even light spotting can be scary but isn’t always a sign of miscarriage; it still deserves medical advice.
  • Emotional support (partner, friends, therapist, support groups) is important whether you are afraid of miscarriage or have already experienced one.

If you tell me how far along you (or the person you’re asking for) are, I can help contextualize these general patterns and answer more specific questions.