How Common Is Miscarriage?

It has been estimated that around 10% to 20% of known pregnancies result in miscarriage. Frequently, miscarriages occur very early into the pregnancy, often before the pregnancy has been identified. This means that the actual number of miscarriages that occur may be significantly higher than this estimate. Another estimate suggests that 23 million miscarriages happen annually on a global scale. 

The loss of a pregnancy is classified as a miscarriage when it occurs prior to reaching 20 weeks of pregnancy. Most miscarriages are caused by chromosomal abnormalities, which result in around 50% of all miscarriages during the first 13 weeks of pregnancy, or the first trimester. These chromosomal abnormalities occur when an egg or sperm has more or less chromosomes than normal, resulting in an abnormal number of chromosomes for the fetus. Chromosomal abnormalities that do not result in a miscarriage will often develop into chronic conditions such as Down syndrome, Patau Syndrome, and trisomy 16. Infants born with these abnormalities typically suffer from a range of birth defects. 

After the first trimester has passed, risk of miscarriage can drop significantly but is not entirely eliminated. Although chromosomal abnormalities account for a high percentage of miscarriages, there are many other factors that are believed to increase the risk of miscarriage. These factors can include:

• Exposure to TORCH diseases
  • Toxoplasmosis 
  • Other infections such as HIV, parvovirus B19, syphilis, and varicella 
  • Rubella 
  • Cytomegalovirus 
  • Herpes simplex virus 
• Infections 
• Uterine abnormalities 
• Being over the age of 35 
• Hormonal imbalances 
• Tobacco, alcohol, or drug use 
• Unmanaged diabetes 
• Radiation 
• Thyroid disease 
• Congenital heart disease 
• Severe kidney disease 
• Malnutrition 
• Autoimmune disorders 
• Certain medications 
• Cervical insufficiency 

Most miscarriages are not the result or consequence of something that someone did or did not do, although many people blame themselves when a miscarriage occurs. The factors that contribute to an increased risk of miscarriage are typically not factors that most people are able to control or even influence, especially those that are related to chromosomal abnormalities, age, or pre-existing conditions. Additionally, miscarriages are not always an indicator of a fertility issue. Around 87% of women who have experienced a miscarriage are capable of having successful pregnancies and births in the future. 

Sources

“Miscarriage”. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/pregnancy-loss-miscarriage/symptoms-causes/syc-20354298 

“Miscarriage matters: the epidemiological, physical, psychological, and economic costs of early pregnancy loss”. National Library of Medicine. https://pubmed.ncbi.nlm.nih.gov/33915094/ 

“Down Syndrome”. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/birth-defects/about/down-syndrome.html 

“Trisomy 13 (also known as Patau syndrome)”. Minnesota Department of Health. https://www.health.state.mn.us/diseases/cy/trisomy13.html 

“A rare description of pure partial trisomy of 16q12.2q24.3 and review of the literature”. National Library of Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC9082733/ 

“Birth Defects”. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/12230-birth-defects 

“Miscarriage”. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/9688-miscarriage