Stillbirth, defined as the loss of a baby at or after 20 weeks of pregnancy, represents a deeply challenging experience for expectant parents. Understanding the statistical chances and contributing factors can provide clarity. This article offers clear, data-driven insights into stillbirth rates across different gestational ages.
Understanding Stillbirth Classifications and Overall Rates
In the United States, stillbirth affects approximately 1 in 175 births, with around 21,000 babies stillborn each year. Medical professionals categorize stillbirths by gestational age to better understand patterns and causes.
These classifications include early stillbirth, which occurs between 20 and 27 completed weeks of pregnancy. Late stillbirth refers to fetal deaths occurring from 28 to 36 completed weeks. Term stillbirth encompasses losses at 37 or more completed weeks of gestation.
Stillbirth Risk by Gestational Age
The statistical risk of stillbirth varies depending on the gestational age, with different trends observed across pregnancy. While the overall number of stillbirths might be lower in earlier weeks compared to later in pregnancy, the rate of loss per ongoing pregnancy is generally higher at the earliest stages of viability.
During the early stillbirth period, from 20 to 27 weeks, the rate of loss per ongoing pregnancy is at its highest point and gradually decreases as the weeks progress within this interval. For instance, the early fetal mortality rate (20-27 weeks) was 2.95 per 1,000 live births and fetal deaths in 2021.
The rate of stillbirth continues to decline during the late stillbirth period, from 28 to 36 weeks, as the fetus becomes more developed. In 2021, the late fetal mortality rate (28 weeks and greater) was 2.80 per 1,000 live births and fetal deaths, remaining largely stable since 2014. For pregnancies reaching term, between 37 and 40 weeks, the stillbirth rate is at its lowest point. However, the risk begins to rise slightly each week after 41 weeks of gestation, which often prompts discussions about labor induction for post-term pregnancies.
Factors That Influence Stillbirth Risk
Several factors can influence the risk of stillbirth throughout pregnancy, falling into categories related to pregnancy complications, maternal health conditions, and maternal characteristics.
Pregnancy and Placental Complications
Pregnancy and placental complications contribute to stillbirth. Issues such as placental abruption, where the placenta separates from the uterine wall prematurely, can occur in 5–10 percent of stillbirths. Problems with the umbilical cord, including knots or compression, account for about 10% of stillbirths. Fetal growth restriction, where a fetus does not grow as expected, is also associated with an increased stillbirth risk, particularly when the fetus is smaller than the third percentile for growth.
Maternal Health Conditions
Maternal health plays a role in stillbirth risk. Pre-existing or gestational conditions like high blood pressure, preeclampsia, and diabetes can increase the chances of stillbirth. For example, gestational diabetes can affect placental function, which in turn elevates stillbirth risk. Infections in the mother or fetus are also linked to stillbirth, especially in early or late stillbirth cases.
Maternal Characteristics
Certain maternal characteristics can also influence stillbirth risk. Carrying multiples, such as twins or triplets, is associated with a higher risk compared to singleton pregnancies. Maternal age, particularly being over 35 years old, can also increase the risk. Racial disparities in stillbirth rates exist, with Black women in the U.S. experiencing stillbirths at more than twice the rate of white women. This disparity is widely understood to reflect systemic inequities in healthcare access and quality rather than inherent biological differences.
Monitoring and Risk Reduction Strategies
While not all stillbirths are preventable, certain proactive measures can help reduce the risk. Engaging in consistent monitoring and adhering to recommended health practices are important.
Fetal Movement Monitoring
Monitoring fetal movement, often referred to as “kick counts,” is a recommended practice starting around 28 weeks of pregnancy. Noticing a significant change or reduction in the baby’s usual movement pattern warrants immediate contact with a healthcare provider. This self-monitoring can provide an early indication of potential concerns.
Regular Prenatal Care
Regular prenatal care appointments are important for risk reduction. Attending all scheduled visits allows healthcare providers to consistently monitor the pregnancy for any potential issues, such as changes in blood pressure, fetal growth, or other indicators that might suggest a heightened risk. These appointments facilitate early detection and management of complications.
Managing Health Conditions
Managing existing health conditions, such as diabetes and high blood pressure, with a healthcare team before and during pregnancy can help mitigate associated risks. Adhering to medical advice and treatment plans for these conditions supports a healthier pregnancy outcome. Avoiding smoking and illicit substance use during pregnancy also contributes to reducing stillbirth risk, as these behaviors are linked to complications like placental abruption and fetal growth restriction.