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Calculating the Odds of Miscarriage

General, the “common” danger of miscarriage is estimated to be between 12% and 15% of acknowledged pregnancies by 20 weeks gestation. But, since there are a number of key components, equivalent to maternal age and consuming, that will enhance danger, how are you going to estimate your private danger of getting a miscarriage? Let’s check out particular danger components for miscarriage, and the way a lot danger these confer.

Some danger components are unavoidable. You possibly can’t change the yr you have been born or whether or not you may have had miscarriages up to now. You possibly can, nevertheless, take a look at avoidable danger components, equivalent to alcohol consumption, so as to scale back your danger.

Odds Ratios of Miscarriage Threat

For some danger components, researchers do not need a flat estimate of the share of regular pregnancies that may miscarry. As an alternative, they’ve calculated odds ratios to point the elevated danger in comparison with girls with out the chance issue.

An odds ratio exhibits the share of elevated danger fairly than the chance of miscarriage. For instance, an odds ratio of 1.5 would imply {that a} lady was 1.5 occasions extra prone to miscarry as a result of a selected danger issue. To find out the chance of miscarriage, you possibly can multiply the quantity of people that ordinarily are anticipated to miscarry by this quantity.

For instance, an odds ratio of 1.5 implies that an individual is 50% extra doubtless than the “common” pregnant individual to miscarry. This doesn’t imply a 50% probability of a miscarriage occurring. For instance, if the chance of miscarriage with out the chance issue is 20%, somebody with that danger issue would have a 30% danger of miscarrying (as a result of 30% is 50% greater than 20%, or 20% multiplied by 1.5 is 30%.)

Recognized Threat Elements for Miscarriage

There are a number of identified danger components for miscarriage, together with the age of the mom and father, life-style components, and medical circumstances. These dangers—both the p.c who will miscarry or the chances ratio of miscarriage—are listed within the desk beneath.

A few of the most typical danger components which were evaluated statistically embrace:

  • Amniocentesis: The danger of miscarriage associated to amniocentesis is now considered as little as .35% or about 1 in 300.
  • Consuming Alcohol: General, analysis exhibits a 1.19 odds ratio of being pregnant loss with publicity to alcohol throughout being pregnant in contrast with people who abstained. Consuming extra alcohol throughout being pregnant will increase miscarriage danger, with the chance growing an estimated 6% to 13% with every further drink consumed per week.
  • Maternal age: The danger of miscarriage is roughly 50% for a lady in her early 40s and as much as 75% at age 45.
  • Paternal age: Whereas we regularly assume most about maternal age, elevated paternal age additionally will increase the chances of miscarriage, though to a lesser extent than elevated maternal age.
  • Preventable infections: Infections are thought to account for round 15% of miscarriages. Many infections haven’t been proven to extend danger, or research have proven blended outcomes. Infections which were clearly related to miscarriage embrace malaria, brucellosis, cytomegalovirus, HIV, dengue fever, influenza virus, and vaginal an infection with bacterial vaginosis. 
  • Earlier miscarriages: Roughly 2% of ladies can have two miscarriages in a row, and 1% of ladies, can have three or extra. Whereas the chances ratio for miscarriage goes up for every subsequent miscarriage, it’s noteworthy that even with 4 or extra prior miscarriages, the p.c of these girls who won’t miscarry is near 50%.
  • Current miscarriage: In distinction to data up to now, getting pregnant inside 6 months of a previous miscarriage doesn’t enhance the chance of a second miscarriage. In actual fact, a shorter interval of fewer than 3 months offers a decrease danger of getting one other miscarriage than happens with a being pregnant that begins 6 months or extra after miscarriage.
  • Secondhand smoke: Publicity to secondhand smoke will increase the chance of miscarriage by 11%.
  • Smoking: The danger associated to smoking in being pregnant carries an odds ratio of 1.23, which works as much as 1.32 for these smoking 10 or extra cigarettes every day. It is thought that smoking accounts for as much as 10% of miscarriages. It is essential to notice that former people who smoke and people who smoke that stopped smoking early on in being pregnant are at decrease danger, so it’s extremely useful to give up smoking earlier than getting pregnant and/or as soon as you discover out.
  • Weight: For ladies who’re underweight—a physique mass index (BMI) lower than 18.5—the chances ratio is 1.08. The percentages ratio of miscarriage is 1.09 for obese girls and between 1.15 and 1.27 for overweight girls.
  • Working atypical and/or lengthy hours: In contrast with these working day shift jobs, the chance of being pregnant loss for evening shift staff is 1.21. Working longer hours than is typical additionally ups the chances ratio for miscarriage to 1.38.

Physique Mass Index (BMI) is a dated, biased measure that doesn’t account for a number of components, equivalent to physique composition, ethnicity, race, gender, and age.

Regardless of being a flawed measure, BMI is extensively used immediately within the medical neighborhood as a result of it’s a reasonable and fast methodology for analyzing potential well being standing and outcomes.

Miscarriage Charges and Threat Elements

The desk beneath illustrates total estimated miscarriage charges by particular danger components. Observe that a few of these components are usually not but properly understood and that the precise figures differ by particular person examine. Additionally, your private danger might differ considerably based mostly on the specifics of your being pregnant and medical historical past.

Typical Miscarriage Charges for Threat Elements

Threat Issue P.c Who Will Miscarry
Mom’s age 30-39 25%
Mom’s age 40-44 50%
Mom’s age >45 75%-95%
2 prior miscarriages 20%
3 prior miscarriages 40%
4 or extra prior miscarriages 54%
Odds Ratio of Miscarriage
Weight problems (BMI > 30) 1.15 to 1.27
Being underweight (BMI < 18.5) 1.08
Father’s age >40 1.6
Consuming alcohol, added danger per drink 1.06 to 1.13 (6% to 13% enhance in added danger per further weekly drink)
Smoking >10 cigarettes every day 1.32

A Phrase From Verywell 

There are some preventable danger components for miscarriage that ladies can work to regulate, however more often than not there’s nothing you are able to do to forestall a miscarriage, and having a miscarriage doesn’t imply that you simply did something fallacious.

Irrespective of how frequent miscarriage is, if it occurs to you it may be devastating. The platitudes folks usually hear, equivalent to, “you possibly can all the time get pregnant once more” do nothing to remove the damage. Whereas miscarriages most frequently happen as a result of a chromosomal abnormality within the child, understanding this will not assist when you miscarry your child. It nonetheless hurts a lot.

You aren’t a statistic. Should you’ve had a miscarriage or are involved you will have a miscarriage, discuss to your physician and attain out for help out of your family members. No person ought to should undergo the nervousness associated to miscarriage alone.

Verywell Household makes use of solely high-quality sources, together with peer-reviewed research, to help the info inside our articles. Learn our editorial course of to study extra about how we fact-check and preserve our content material correct, dependable, and reliable.
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  6. du Fossé NA, van der Hoorn MP, van Lith JMM, le Cessie S, Lashley EELO. Superior paternal age is related to an elevated danger of spontaneous miscarriage: a scientific evaluation and meta-analysis. Hum Reprod Replace. 2020;26(5):650-669. doi:10.1093/humupd/dmaa010

  7. Giakoumelou S, Wheelhouse N, Cushieri Ok, et al. The function of an infection in miscarriage. Hum Reprod Replace. 2016. 22(1):116-133. doi:10.1093/humupd/dmv041

  8. Garrido-Giminez C, Alijotas-Reig J. Recurrent miscarriage: causes, analysis and administration. 2014;91(1073). doi:10.1136/postgradmedj-2014-132672

  9. Sundermann AC, Hartmann KE, Jones SH, Torstenson ES, Velez Edwards DR. Interpregnancy interval after being pregnant loss and danger of repeat miscarriage. Obstet Gynecol. 2017;130(6):1312-1318. doi:10.1097/AOG.0000000000002318

  10. Pineles BL, Park E, Samet JM. Systematic evaluation and meta-analysis of miscarriage and maternal publicity to tobacco smoke throughout being pregnant. Am J Epidemiol. 2014;179(7):807-823. doi:10.1093/aje/kwt334

  11. Balsells M, Garcia-Patterson A, Corcoy R. Systematic evaluation and meta-analysis on the affiliation of prepregnancy underweight and miscarriage. Eur J Obstet Gynecol Reprod Biol. 2016;207:73-79. doi:10.1016/j.ejogrb.2016.10.012

  12. Cai C, Vandermeer B, Khurana R, Nerenberg Ok, Featherstone R, Sebastianski M, Davenport MH. The influence of occupational shift work and dealing hours throughout being pregnant on well being outcomes: a systematic evaluation and meta-analysis. Am J Obstet Gynecol. 2019;(6):563-576. doi:10.1016/j.ajog.2019.06.051

By Krissi Danielsson

Krissi Danielsson, MD is a health care provider of household medication and an advocate for individuals who have skilled miscarriage. 

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