If you’re searching “miscarriage risk by week,” you’re usually looking for one thing: reassurance and clarity. Early pregnancy can feel like a long stretch of uncertainty, and it’s normal to want numbers. A risk of miscarriage by week estimate can help you understand the overall pattern risk is highest very early. It steadily decreases as pregnancy progresses but it can’t predict what will happen in any one person.
This guide explains miscarriage week by week, how to read a miscarriage by week chart, and how a miscarriage risk calculator by week typically works using calm, patient-care language and plain explanations.
Important note: This article is educational and not a diagnosis. If you have bleeding, pain, dizziness, fever, or you’re worried for any reason, contact a qualified clinician or your local emergency service.
What “miscarriage risk by week” actually means
When people talk about miscarriage probability by week or miscarriage likelihood by week, they may mean one of two things:
- Risk remaining at a given point in pregnancy (for example: “Now that I’m 8 weeks, what is the chance of miscarriage going forward?”)
- Weekly miscarriage rate by week (the chance of loss during that particular week)
Many online charts and tools show the first type: how the remaining risk drops as gestational age increases.
Also, definitions vary by country and data source. For example, UK information commonly describes miscarriage as pregnancy loss before 24 weeks, and notes that most losses happen early.
How common is miscarriage?
Miscarriage is sadly common and not a sign you did anything wrong.
- The RCOG notes that miscarriage can affect about 1 in 5 pregnancies in the first 3 months after a positive test.
- A UK hospital patient leaflet notes that most miscarriages happen in the first 12 weeks, with early miscarriage occurring about 10–20 times in every 100 pregnancies, while late miscarriage after 12 weeks is less common (about 1–2 in every 100 pregnancies).
These numbers differ across studies because early losses can be missed (especially before a pregnancy is confirmed), and because different datasets include different populations.
The big picture: miscarriage risk decreases week by week
Here’s the overall trend behind most miscarriage statistics by week:
- Weeks 3–5: highest uncertainty and highest “remaining risk” in many charts (often because very early pregnancies are still establishing).
- Weeks 6–9: risk usually drops quickly (especially once pregnancy dating is clearer and care begins).
- Weeks 10–12: risk continues to decline and starts to “flatten.”
- After 12 weeks: risk is generally much lower than in early weeks. Many people choose to share pregnancy news around this time because the risk is reduced.
Miscarriage rates by week vs. “remaining risk” (why charts can confuse)
A common confusion happens when someone reads a miscarriage rate by week chart as if it’s a guarantee. It isn’t.
- A weekly miscarriage rate by week is like: “chance of loss during week 9.”
- A remaining risk is like: “now that I’m at week 9, what is my chance of miscarriage from this point forward?”
Most “week-by-week calculators” present remaining risk because it’s easier to understand and feels more relevant.
A practical week-by-week view (how most calculators summarize risk)
Many tools present miscarriage percentages by week like this:
- Around 3–4 weeks: higher remaining risk
- Around 6–7 weeks: moderate remaining risk
- Around 8–10 weeks: low single-digit remaining risk
- Around 12–14 weeks: usually ~1–2% remaining risk range in many references
- Around 15–20 weeks: very low remaining risk, but not truly zero
A key patient-care point: a chart is a population estimate, not your personal diagnosis. Your clinician uses your history, exam, and ultrasound findings to give personalized guidance.
What a miscarriage risk calculator by week typically does
A miscarriage risk calculator by week usually asks for:
- Gestational age (week + days)
- Sometimes maternal age (because risk tends to increase with age)
Then it applies a population-level risk curve to estimate:
- Chance of miscarriage by week (remaining risk)
- Chance of not miscarrying (continuing pregnancy probability)
The RCOG highlights the age effect clearly: risk rises with age around 20% at age 30 and around 50% over age 40 (population averages).
Limitations
A responsible calculator should clearly state that estimates may not apply well if someone has:
- IVF/assisted reproduction
- Multiple pregnancy (twins+)
- Prior recurrent miscarriage, known uterine/cervical issues, or major medical conditions
- Symptoms that require urgent assessment (bleeding, severe pain, fever)
Why most miscarriages happen early
This is one of the most important “why” questions.
A widely stated reason is that many early miscarriages are linked to chromosome problems that happen by chance. A UK hospital leaflet explains that the most common cause in early miscarriage is a chromosomal problem that prevents normal development.
That’s also why many clinicians reassure patients: in most cases, it isn’t caused by exercise, sex, or something you did.
“Is it my fault?” Common myths, gently answered
If you’re worried you “caused” a miscarriage, you’re not alone. The RCOG states there is no evidence that stress can cause miscarriage, and that having sex in early pregnancy is not associated with miscarriage.
Also, it’s normal to look for a single reason, but many early losses happen without a clear, identifiable cause in an individual case.
When to contact a clinician
Even when statistics are reassuring, symptoms should be taken seriously. Seek medical advice urgently if you have:
- Heavy bleeding
- Severe or worsening pain
- Fever, chills, or feeling unwell
- Dizziness/fainting
- Any symptom that scares you
(These are common “safety-net” warnings across clinical patient leaflets and services.)
How to use a miscarriage by week chart in a healthy way
A miscarriage by week chart is most helpful when you use it as:
- A way to understand the direction of change (risk drops with time)
- A tool to reduce “doom scrolling” by giving a single reference point
Try not to use it as:
- A day-by-day prediction of symptoms
- A replacement for clinical evaluation
If anxiety is intense, consider limiting how often you check numbers. Sometimes “more data” increases worry instead of reducing it.
