Miscarriage Odds Calculator

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Reviewed by: Dr. Elena Richardson, OBGYN Board Certified Obstetrician and Gynecologist • Medical Statistics Consultant

The Miscarriage Odds Calculator estimates the probability of a healthy pregnancy based on your current week of gestation and maternal age, using data from large-scale clinical studies.

Miscarriage Odds Calculator

Enter your details and click calculate to see your results.

Miscarriage Odds Calculator Formula

Probability of Viability = 1 – (Base RiskWeek × Age Factor × History Factor)

Source: National Institutes of Health (NIH) – Risk Factors for Miscarriage | ACOG Guidelines

Variables:

  • Maternal Age: The risk of chromosomal abnormalities increases significantly after age 35.
  • Weeks Pregnant: Risk drops exponentially as the pregnancy progresses, especially after a heartbeat is detected.
  • Previous Miscarriages: History of recurrent loss can statistically increase the likelihood of subsequent loss.

What is a Miscarriage Odds Calculator?

A miscarriage odds calculator is a statistical tool used to determine the probability of a pregnancy continuing to full term versus the risk of loss. Most miscarriages occur in the first trimester (the first 12 weeks), often due to chromosomal issues that are beyond the mother’s control.

This tool aggregates data from thousands of clinical outcomes to show how the “viability” (the chance of success) increases every day and week that passes. Understanding these odds can provide significant peace of mind to expecting parents.

How to Calculate Miscarriage Odds (Example)

  1. Identify your current gestational week (e.g., Week 8).
  2. Identify maternal age (e.g., 32 years).
  3. Find the baseline risk for Week 8 (approx. 5%).
  4. Adjust for age: Ages 30-34 typically have a multiplier of 1.0x to 1.1x.
  5. Calculate: 5% × 1.1 = 5.5% current risk.
  6. Subtract from 100 to find the probability of success: 100% – 5.5% = 94.5%.

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Frequently Asked Questions (FAQ)

When does the risk of miscarriage drop the most? The risk drops most significantly after the 8th week once a fetal heartbeat is detected, and again after the 12th week.

Does maternal age affect the odds? Yes, the risk is approximately 10-15% for women in their 20s, but can rise to over 50% for women over age 45.

Are these calculators 100% accurate? No, these provide statistical averages. Every pregnancy is unique and depends on specific medical conditions.

What is the chance of a healthy pregnancy at 12 weeks? By week 12, the statistical risk of miscarriage usually drops below 2-3% for most women.

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