# What is my miscarriage risk?

Shows the published miscarriage risk for your age (Magnus 2019, 421,201 pregnancies) and, after a normal scan with a heartbeat at 6 to 10 weeks, the risk by week (Tong 2008).

- Page: https://www.acalculator.org/health/miscarriage-risk-calculator
- JSON spec: https://www.acalculator.org/health/miscarriage-risk-calculator.json
- Version: e67946432484

## Default answer

Example with the default inputs (Your age 30, Normal scan with a heartbeat? Not yet): For age 30, the published miscarriage risk is 10.8% (age group 30 to 34).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| age | Your age | Your age in whole years at the start of the pregnancy. |
| scan | Normal scan with a heartbeat? | Whether an ultrasound at 6 to 10 weeks showed one baby with a heartbeat, with no bleeding or pain. |
| wk | Weeks pregnant at that scan | Completed weeks of pregnancy at the scan, 6 to 10 (6 weeks and 3 days counts as 6). |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| ageRisk | Risk for your age | The share of pregnancies that ended in miscarriage for women in your age group (Magnus 2019). |
| ageGroup | Age group | The age group of the published table. |
| afterScan | Risk after a normal scan at this week | The share of women with no symptoms and a normal scan at this week who later miscarried (Tong 2008). |

## Method

Two published tables: miscarriage risk by maternal age group (Magnus 2019), and risk after a normal scan with a heartbeat by completed week, 6 to 10 (Tong 2008).

## Assumptions

- The age table counts all recognized pregnancies in Norway, 2009 to 2013, with induced abortions handled as in the paper.
- The week table is from 696 women with no symptoms and one baby with a heartbeat at their first visit in Australia.
- The two numbers come from different studies and are not combined.

## Worked examples

1. age = 30, scan = no gives ageRisk = 10.8%, ageGroup = 30 to 34. Source: Magnus 2019, BMJ, Table 1: age 30 to 34, 13,362 of 123,266 pregnancies, 10.8%.
2. age = 27, scan = no gives ageRisk = 9.8%, ageGroup = 25 to 29. Source: Magnus 2019, Table 1: age 25 to 29, 9.8% (the lowest group).
3. age = 42, scan = yes, wk = 7 gives ageRisk = 32.2%, ageGroup = 40 to 44, afterScan = 4.2%. Source: Magnus 2019, Table 1: age 40 to 44, 32.2%; Tong 2008: 4.2% after a normal visit at 7 weeks.
4. age = 46, scan = yes, wk = 9 gives ageRisk = 53.6%, ageGroup = 45 or older, afterScan = 0.5%. Source: Magnus 2019, Table 1: 45 and over, 53.6%; Tong 2008: 0.5% at 9 weeks.
5. age = 19, scan = yes, wk = 6 gives ageRisk = 15.8%, ageGroup = under 20, afterScan = 9.4%. Source: Magnus 2019, Table 1: under 20, 15.8%; Tong 2008: 9.4% at 6 completed weeks.

## FAQ

### How common is miscarriage?

In a study of all 421,201 pregnancies in Norway from 2009 to 2013 (Magnus 2019), 12.8% of recognized pregnancies ended in miscarriage.

### How does age change the risk of miscarriage?

The risk was lowest at ages 25 to 29 (9.8%) and rose quickly after 30: 16.7% at 35 to 39, 32.2% at 40 to 44, and 53.6% at 45 and over. Women under 20 had a risk of 15.8%.

### Does seeing a heartbeat lower the risk?

Yes. Tong and others (2008) followed 696 women with no symptoms whose first visit, between 6 and 11 weeks, showed one baby with a heartbeat. Only 1.6% miscarried. The paper gives the risk by completed week from 6 to 10: 9.4% at 6 weeks, 4.2% at 7, 1.5% at 8, 0.5% at 9, and 0.7% at 10.

### Does a past miscarriage raise the risk?

Yes. In the Norwegian study the age-adjusted odds of a miscarriage were 1.54 times higher after one miscarriage, 2.21 times after two in a row, and 3.97 times after three or more. The calculator does not apply these, because they are odds ratios, not risks for your age group.

### Why are the two numbers different?

They answer different questions. The age risk counts all recognized pregnancies from the start. The scan risk counts only pregnancies that already had a normal scan with a heartbeat, which have come through the riskiest weeks.

## Sources

- Magnus MC, Wilcox AJ, Morken NH, Weinberg CR, Håberg SE. Role of maternal age and pregnancy history in risk of miscarriage: prospective register based study. BMJ. 2019;364:l869. https://doi.org/10.1136/bmj.l869
- Tong S, Kaur A, Walker SP, Bryant V, Onwude JL, Permezel M. Miscarriage risk for asymptomatic women after a normal first-trimester prenatal visit. Obstet Gynecol. 2008;111(3):710-714. https://doi.org/10.1097/AOG.0b013e318163747c