Pregnancy Loss Prevalence, Causes, & Risk Factors

In most instances, those who have experienced a miscarriage or stillbirth can have successful pregnancies and healthy babies in the future. Early pregnancy losses usually do not result in uterine issues that can contribute to infertility. However, it is important to be aware of potential risk factors and complications that may arise in future pregnancies, especially since the odds can vary depending on whether the loss was a miscarriage or stillbirth. 

Most women who have a miscarriage will have healthy pregnancies and healthy babies in the future. It is estimated that only 1 percent of women experience recurrent miscarriages. However, the risk of a future miscarriage is estimated to be around 20 percent after the initial miscarriage has occurred. In women who have recurrent miscarriages, the risk of miscarriage continues to increase. Projected risks for miscarriages are included below:

• One miscarriage: 20 percent risk of a future miscarriage
• Two miscarriages: 28 percent risk of a future miscarriage 
• Three or more miscarriages: 43 percent risk of a future miscarriage 

These estimates are similar to those that are projected for stillbirths. Most women who have previously had a stillbirth can have healthy babies if they become pregnant again in the future. It is estimated that 1 to 2 percent of women who have experienced a stillbirth will have another during a future pregnancy. The likelihood and risk of having another stillbirth are often influenced by other factors such as whether the mother uses tobacco or has a high BMI, but can vary significantly. 

Taking care of physical and emotional health after a pregnancy loss is essential and can help increase the chances of having a healthy pregnancy in the future. Although the cause of miscarriage or stillbirth often is unknown, there is value in proactively practicing healthy lifestyle behaviors to reduce potential complications. This can include getting regular exercise, eating a balanced diet, and managing chronic conditions as much as possible. Individuals who are concerned about their risk for future stillbirth or miscarriage are encouraged to contact their healthcare provider to discuss options to increase the likelihood of having a successful pregnancy. 

Sources

“Pregnancy after miscarriage: What you need to know”. Mayo Clinic. https://www.mayoclinic.org/healthy-lifestyle/getting-pregnant/in-depth/pregnancy-after-miscarriage/art-20044134 

“Pregnancy risk factors: Previous miscarriage or stillbirth”. All About Women Advanced Gynecology. https://www.allaboutwomenmd.com/knowledge-center/previous-miscarriage-or-stillbirth.html

Although the United States is one of the wealthiest countries in the world, it has a high infant mortality rate in comparison to other high-income and developed countries. Understanding the major contributors or causes of infant mortality is crucial in efforts to effectively reduce the death rate. The leading causes of infant mortality in the United States in 2020 were:

• Birth defects
• Preterm birth and low birth weight 
• Sudden infant death syndrome 
• Injuries 
• Maternal pregnancy complications 

Birth defects are structural changes that are present in a baby’s body at the time of birth and are often accompanied by serious health conditions. Many birth defects are found during the first year of life. Some are visibly noticeable, such as a cleft lip.  But other conditions, such as hearing loss and congenital heart defects, can only be discovered through specialized tests. Additionally, although some birth defects have a known cause, such as fetal alcohol syndrome, there are numerous birth defects that have no identifiable cause. In these instances, birth defects may be influenced by factors such as genes, parental lifestyle and health behaviors, or exposure to potentially harmful elements in the environment. 

Preterm birth occurs when a baby is born before the 37th week of pregnancy. Since babies continue to grow and develop throughout the last weeks of pregnancy, preterm birth can limit the development of vital organs such as the lungs, liver, and brain. Low birth weight is often associated with preterm births and can increase the risk for additional complications since the baby may struggle to eat, gain and maintain weight, and recover from infections. Preterm birth and low birth weight were attributed to 16% of infant deaths in the United States in 2020.  

Sudden infant death syndrome (SIDS) is a term used to describe the death of a baby under the age of one year, whose death does not have a known cause. It is distinguished from sudden unexpected infant death (SUID), which is a broader term used to reference all sudden infant deaths or those that cannot be distinguished directly from SIDS. If the medical examiner or coroner cannot determine the cause of death, it may be categorized as SIDS on the death certificate. Similarly, when babies die due to injuries such as suffocation, strangulation, or other injuries, these may be categorized as SUID. 

Maternal health complications during pregnancy can also contribute to infant mortality. Some complications that commonly occur include infections, heart conditions, blood clots, high blood pressure, and stroke. These complications can also contribute to stillbirth, miscarriage, or the death of the mother during pregnancy or shortly after giving birth. It is important to note that if potential complications are identified early in the pregnancy, they may be managed more effectively or even prevented entirely with appropriate treatment and monitoring. 

Sources

“Infant Mortality”. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/maternal-infant-health/infant-mortality/?CDC_AAref_Val=https://www.cdc.gov/reproductivehealth/maternalinfanthealth/infantmortality.htm 

“About Birth Defects”. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/birth-defects/about/?CDC_AAref_Val=https://www.cdc.gov/ncbddd/birthdefects/facts.html 

“Fetal Alcohol Syndrome”. Mayo Clinic. https://www.mayoclinic.org/diseases-conditions/fetal-alcohol-syndrome/symptoms-causes/syc-20352901 

“Preterm Birth”. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/maternal-infant-health/preterm-birth/?CDC_AAref_Val=https://www.cdc.gov/reproductivehealth/maternalinfanthealth/pretermbirth.htm 

“Definitions and Terms”. Safe to Sleep. https://safetosleep.nichd.nih.gov/about/terms 

“What is SIDS/SUID?” American SIDS Institute. https://sids.org/what-is-sidssuid/ 

Several socioeconomic factors influence the rates of pregnancy loss in the United States. These socioeconomic factors include: 

• Low socioeconomic status or position
• Educational attainment
• Insurance coverage 
• Race
• Ethnicity 

Socioeconomic status is often a key determinant in pregnancy loss rates. Low socioeconomic status can result in disparities in access to education, quality healthcare and resources. This often correlates with higher pregnancy loss rates among low-income and poverty-level populations. Pregnant women with low socioeconomic status also have significantly more depressive symptoms and higher stress levels, particularly during the third trimester. Low socioeconomic status is often associated with limited access to prenatal care, food insecurity or inadequate nutrition, and increased environmental exposure to hazards in disadvantaged communities. 

Insurance coverage can also significantly affect access, quality, and level of care received during pregnancy. Interrupted care and delayed access to services through Medicaid can result in adverse health and birth outcomes. Unfortunately, many women with Medicaid are less likely to start prenatal care during their first trimester of pregnancy and less likely to receive suitable prenatal care when compared to women with private insurance. While this does not result in noticeable differences in birth outcomes or pregnancy loss, it demonstrates how access to care can vary significantly for low-income people. 

Numerous studies have documented increased maternal death in women with lower education levels, public or no insurance coverage, or minority race and ethnicity. Racial and ethnic disparities often have a prominent influence on pregnancy loss and maternal and infant health. For example, the pregnancy-related mortality rate for Black women who have completed a college education or beyond is 5.2 times higher than that for white women with the same level of educational attainment. Similarly, Black women who receive adequate prenatal care have higher rates of infant mortality even when compared to white women who receive little or no prenatal care, suggesting that issues such as structural racism influence pregnancy loss even in the absence of socioeconomic factors.

Sources 

“Fact Sheet: Women & Socioeconomic Status”. American Psychological Association. https://www.apa.org/pi/ses/resources/publications/women 

“Access in Brief: Pregnant Women and Medicaid”. Medicaid and CHIP Payment and Access Commission. https://www.macpac.gov/wp-content/uploads/2018/11/Pregnant-Women-and-Medicaid.pdf 

“Social Determinants of Pregnancy-Related Mortality and Morbidity in the United States: A Systematic Review”. National Library of Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC7104722/ 

“Racial Disparities in Maternal and Infant Health: Current Status and Efforts to Address Them”. KFF. https://www.kff.org/racial-equity-and-health-policy/issue-brief/racial-disparities-in-maternal-and-infant-health-current-status-and-efforts-to-address-them/ 

“Why Are Black Mothers at Higher Risk for Miscarriage?” WebMD. https://www.webmd.com/baby/features/why-black-mothers-higher-risk-miscarriage 

Maternal health has a direct role in the incidence of pregnancy loss and stillbirth, most notably through the influence of several factors. While this does not mean that the mother caused the pregnancy loss, it is important to acknowledge that the mother’s health can affect the outcome of the pregnancy. Common factors that influence pregnancy loss and stillbirth include: 

• Pre-existing medical conditions 
• Prenatal care 
• Maternal age 
• Lifestyle choices 
• Healthcare access 
• Socioeconomic factors 

Pre-existing medical conditions such as hypertension, autoimmune disorders, and diabetes can increase the risk of pregnancy complications, especially if they are not effectively managed. Once a pregnancy has been identified, maintaining regular check-ups and screenings enables healthcare providers to discover potential health concerns early enough to provide the necessary interventions to support the well-being of mother and child. 

Advanced maternal age has been found to be correlated with stillbirth and pregnancy loss. Advanced maternal age, generally defined as pregnancy at 35 years or older, has been found to be correlated with stillbirth and pregnancy loss. This increased risk is primarily associated with biological factors, such as the development of chromosomal abnormalities. Furthermore, advancing age is also associated with a higher prevalence of underlying maternal health conditions.

Separately, modifiable lifestyle choices and environmental factors can have a significant impact on maternal and fetal health, resulting in an increased risk of complications. Smoking, alcohol, and substance use often have a direct association with adverse pregnancy outcomes. Additionally, factors such as poor nutrition, high stress levels, and exposure to environmental toxins are also recognized contributors. 

Healthcare access is another pivotal factor in relation to pregnancy loss and stillbirth. For some pregnant women, access is compromised because there are very few medical facilities within the community, prenatal care is not an option at available facilities, or only basic care is offered to patients. Similarly, there may be limitations based on whether patients have private, public, or no insurance coverage. Minimal healthcare access is often adjacent to the socioeconomic factors that influence the incidence of pregnancy loss, such as inadequate nutrition, poverty, status or position, educational attainment, and more. 

In consideration of these factors, efforts to reduce the incidence of pregnancy loss and stillbirth should include a greater focus on addressing and improving maternal health. Providing education regarding healthy lifestyle choices, increasing access to healthcare services, and ensuring the availability of comprehensive prenatal care are all actions that can proactively address maternal health outcomes. Additionally, focusing on providing more widespread support that is inclusive of individuals from marginalized groups can further reduce the prevalence of pregnancy loss.

Sources

“Pregnancy Loss (Before 20 Weeks of Pregnancy)”. U.S. Department of Health and Human Services. https://www.nichd.nih.gov/health/topics/factsheets/pregnancyloss 

“Advanced Maternal Age”. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/22438-advanced-maternal-age 

“March of Dimes Research Shows Access to Care Worsening for Millions”. March of Dimes. https://www.marchofdimes.org/about/news/march-dimes-research-shows-access-to-care-worsening-millions 

Although the exact causes of stillbirth can be difficult to determine, researchers have identified several potential causes or contributing factors to stillbirth. It is important to note that in most instances, the cause of a stillbirth will remain unknown even after significant testing. However, analyses of data from the Stillbirth Collaborative Research Network (SCRN) have suggested that stillbirths often result from the following potential causes or contributing factors:

• Pregnancy and labor complications
  • Preterm labor 
  • Pregnancy with twins or triplets 
  • Separation of the placenta 
• Issues with the placenta, namely insufficient blood flow 
• Birth defects and fetal genetic abnormalities 
• Infection
  • Escherichia coli 
  • Group B Streptococcus 
  • Enterococcus 
• Issues with the umbilical cord, such as knotting or squeezing 
• High blood pressure
  • Preeclampsia 
  • Chronic high blood pressure before pregnancy 
• Medical problems before pregnancy, such as a chronic condition like diabetes 

Other potential factors contributing to an increased likelihood of stillbirth include exposure to trauma or unhealthy lifestyle behaviors such as tobacco, alcohol, and substance use. However, doctors consider stillbirth to be a multifactorial occurrence, meaning that multiple factors or potential causes may be involved. This can make it difficult for healthcare providers to determine the exact cause of the loss, even with comprehensive testing. The enormous emotional impact of stillbirth on those affected further highlights the need for further research, education, and specialized support.

For this reason, ongoing efforts aim to increase awareness and research on stillbirth prevention. By addressing the significant causes of stillbirth and reducing the likelihood by targeting specific risk factors, researchers and healthcare professionals may eventually be able to reduce the incidence of stillbirth. Likewise, individuals and families impacted by the intense emotional toll of stillbirth will be more likely to receive adequate and appropriate support.  

Sources

“What are possible causes of stillbirth?” U.S. Department of Health and Human Services. https://www.nichd.nih.gov/health/topics/stillbirth/topicinfo/causes 

The United States has the highest infant mortality rate in comparison to other high-income countries. When mortality data were analyzed in 2021, the United States was found to have an infant mortality rate of 5.4 deaths per 1,000 live births. The leading causes of infant mortality in 2021 included: 

• Birth defects
• Preterm birth and low birth weight 
• Sudden infant death syndrome (SIDS)
• Injuries 
• Maternal pregnancy complications 

Within the United States, the highest infant mortality was observed in the South, the Midwest, and Alaska. Additionally, only 19 states were able to meet the targeted objective of reducing infant deaths to 5.0 per 1,000 live births. Ethnic and racial disparities have also emerged from the high infant mortality rate with a leading rate of 10.6 infant deaths per 1,000 live births among non-Hispanic Blacks. The breakdown of infant mortality rates by race and ethnicity for 2021 indicated the following findings:

• Non-Hispanic Blacks: 10.6 
• Non-Hispanic Native Hawaiian or other Pacific Islander: 7.8 
• Non-Hispanic American Indian/Alaska Native: 7.5 
• Hispanic: 4.8 
• Non-Hispanic White: 4.4 
• Non-Hispanic Asian: 3.7 

Given the significance of the high infant mortality rate in the United States, efforts are being made to improve birth outcomes and gradually reduce infant mortality. Rate reduction can be achieved by addressing social and health risk factors, acknowledging the need to improve quality and access to maternal pregnancy care, and developing strategies to reduce ethnic and racial disparities. Working collaboratively with healthcare providers and communities to increase initiatives and education regarding the leading causes of infant death can improve the likelihood of attaining better outcomes for all infants in the future. 

Sources

“U.S. Health Care from a Global Perspective, 2022: Accelerating Spending, Worsening Outcomes”. The Commonwealth Fund. https://www.commonwealthfund.org/publications/issue-briefs/2023/jan/us-health-care-global-perspective-2022 

“Infant Mortality”. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/maternal-infant-health/infant-mortality/?CDC_AAref_Val=https://www.cdc.gov/reproductivehealth/maternalinfanthealth/infantmortality.htm

Stillbirth typically affects around 1 in 160 pregnancies each year in the United States, and there were around 21,000 reported cases of stillbirth in 2020. Improvements in maternity care have helped to reduce the occurrence of stillbirth. However, the decline has slowed in recent years, and it remains a significant concern around the world. Among pregnancy loss, stillbirth is differentiated from miscarriage based on the number of weeks of pregnancy before fetal death. Stillbirths are characterized by fetal death after 20 weeks, whereas miscarriages are characterized by fetal death before 20 weeks. There are also three classifications of stillbirths in relation to the weeks of pregnancy: 

• Early stillbirth: Fetal death between 20 and 27 weeks of pregnancy 
• Late stillbirth: Fetal death between 28 and 36 weeks of pregnancy 
• Term stillbirth: Fetal death during the 37th week of pregnancy or beyond 

Stillbirths can affect any pregnancy, and healthcare experts are still learning what contributes to this form of pregnancy loss. There are risk factors that can increase the likelihood of a stillbirth occurring during pregnancy. These factors include:

•  Chronic health conditions
•  Previous pregnancy complications
•  High-stress levels
•  Substance use
•  Limited access to resources and prenatal care
•  Being within certain age groups, such as adolescents and women aged 35 or older. 

Healthcare providers need to identify potential risk factors and address them with patients early in the pregnancy to reduce the incidence of stillbirth. Although there is much that remains unknown about the cause of stillbirth, reducing health disparities among patient populations and proactively working with patients to introduce more healthy lifestyle behaviors can improve chances for positive outcomes. Additionally, numerous public health initiatives and studies are being conducted to help healthcare professionals better understand the cause of stillbirth and how to prevent it. 

Sources

“Stillbirth”. March of Dimes. https://www.marchofdimes.org/find-support/topics/miscarriage-loss-grief/stillbirth 

“Data and Statistics on Stillbirth”. U.S. Centers for Disease Control and Prevention. https://www.cdc.gov/stillbirth/data-research/?CDC_AAref_Val=https://www.cdc.gov/ncbddd/stillbirth/data.html 

“Stillbirth”. Cleveland Clinic. https://my.clevelandclinic.org/health/diseases/9685-stillbirth 

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