Miscarriage Risk Calculator NHS
This independent UK guidance checker helps you understand factors and symptoms that may be relevant to miscarriage assessment. It does not calculate a personal miscarriage percentage because NHS and NICE guidance does not provide a simple validated home formula that can safely diagnose or predict miscarriage from a few inputs.
Early pregnancy miscarriage guidance checker
Why this page does not give a percentage
Miscarriage diagnosis is not made from a simple online risk score. NICE recommends clinical assessment and, when indicated, transvaginal ultrasound. At very early gestations, one ultrasound cannot always guarantee an accurate diagnosis and repeat scanning may be required. NICE also says not to use gestational age from the last menstrual period alone to decide whether a fetal heartbeat should be visible.
Symptoms that need medical assessment
The NHS says vaginal bleeding is the main symptom of miscarriage, while lower tummy pain or cramping, fluid loss and passage of tissue can also occur. Bleeding and pain do not always mean miscarriage. If you are pregnant and have bleeding or concerning symptoms, contact your maternity unit, early pregnancy unit or NHS 111 as appropriate.
Call 999 if you are pregnant with vaginal bleeding and have severe tummy pain, shoulder pain, feel faint or severely dizzy, lose consciousness, or have heavy bleeding soaking a pad soon after putting it on.
Factors associated with miscarriage
The NHS lists several factors that may increase the chance of miscarriage, including maternal age 35 or over and some health conditions. A risk factor does not mean a miscarriage will happen, and this page does not turn risk factors into a personal probability.
How miscarriage is assessed
NICE recommends ultrasound to identify the pregnancy location and assess fetal development and heartbeat. Depending on findings, repeat ultrasound and/or hCG testing may be needed. Pregnancy of unknown location and ectopic pregnancy require particular clinical follow-up.
Threatened miscarriage and progesterone
NICE recommends vaginal micronised progesterone for a specific group: women with scan-confirmed intrauterine pregnancy who have vaginal bleeding and have previously had a miscarriage. Treatment decisions must be made by the clinical team; this checker does not recommend or prescribe treatment.
Worked example
Someone at 8 weeks with light bleeding and mild cramps cannot safely be assigned a miscarriage percentage by this page. NHS/NICE guidance supports contacting the appropriate pregnancy service for assessment. Ultrasound findings and, where appropriate, follow-up testing are more informative than a home risk score.
Limitations
This tool cannot confirm pregnancy location, fetal heartbeat, viability, ectopic pregnancy or miscarriage. It does not replace ultrasound, hCG testing, examination or clinical judgement. Symptoms can change quickly, so seek urgent help when warning signs are present.
Authoritative Sources
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FAQs
Can an online calculator tell me my exact miscarriage risk?
Not reliably from a few home inputs. Individual assessment depends on clinical history, symptoms and, when appropriate, ultrasound and laboratory testing.
Does bleeding always mean miscarriage?
No. Bleeding in pregnancy can have different causes, but it should be assessed according to its severity and any accompanying symptoms.
Can one early scan always diagnose miscarriage?
No. NICE states that one ultrasound cannot be guaranteed 100% accurate, particularly very early in pregnancy, and repeat scanning may be required.
When should I call 999?
The NHS advises emergency help for pregnancy bleeding with severe tummy pain, shoulder pain, fainting or loss of consciousness, severe dizziness, or heavy bleeding soaking a pad soon after it is put on.
Disclaimer: This is an educational guidance checker, not a diagnostic or predictive medical tool. If you have bleeding, pain or other concerning symptoms in pregnancy, seek appropriate NHS care.