Stillbirth, the loss of a baby at or after 20 weeks of pregnancy, is a profound and challenging experience for families. This differs from a miscarriage, which refers to a pregnancy loss occurring before 20 weeks of gestation. Understanding the statistical likelihood of stillbirth as pregnancy progresses can offer clarity and context for expectant parents.
Understanding Stillbirth Rates
Stillbirth rates are expressed as the number of stillbirths per 1,000 or 10,000 pregnancies. This “fetus-at-risk” method provides a clearer picture of the actual risk. Stillbirth is a relatively uncommon event, occurring in approximately 1 out of every 160 pregnancies in the United States.
The risk of stillbirth increases with advancing gestational age, particularly once a pregnancy reaches or extends beyond its estimated due date. While the overall rate remains low, this gradual increase is a subject of ongoing medical research and discussion regarding optimal delivery timing. These rates provide a general understanding of population trends rather than predicting individual outcomes.
Weekly Stillbirth Risk
The likelihood of stillbirth changes as pregnancy progresses. At 37 weeks of gestation, the risk of stillbirth is approximately 0.46 per 1,000 pregnancies.
As pregnancy continues, the risk gradually rises. By 38 weeks, the rate increases to about 0.65 per 1,000, and at 39 weeks, it moves to approximately 0.84 per 1,000 pregnancies. This upward trend continues into the full-term period, which spans from 39 weeks through 40 weeks and 6 days.
Reaching 40 weeks of gestation, the stillbirth rate approaches 1.08 per 1,000 pregnancies. The increase becomes more noticeable in post-term pregnancies, defined as those extending to 42 weeks or beyond. At 41 weeks, the risk climbs to about 1.45 per 1,000, and by 42 weeks, it can reach approximately 2.63 per 1,000 pregnancies. Even at 42 weeks, the vast majority of pregnancies result in a live birth.
Factors Influencing Stillbirth Risk
Beyond gestational age, several factors can influence the overall risk of stillbirth. Maternal health conditions, such as poorly controlled pre-existing or gestational diabetes, high blood pressure disorders like preeclampsia, and obesity, can elevate the risk. These conditions can impact the placental environment and fetal well-being.
Placental complications include placental abruption, where the placenta separates from the uterine wall prematurely, which can lead to complications. Placental insufficiency, where the placenta does not adequately supply nutrients and oxygen to the fetus, also increases risk. Problems with the umbilical cord, such as true knots or compression, may restrict blood flow to the baby.
Fetal conditions, including certain genetic abnormalities or structural birth defects, can contribute to stillbirth. Infections in the mother or fetus, such as those caused by certain bacteria or viruses, have been associated with increased risk. Lifestyle choices, including smoking and substance use during pregnancy, are also recognized risk factors. Despite extensive research, a significant number of stillbirths remain unexplained even after thorough investigation.
Monitoring and Medical Guidance
Regular prenatal care is important for monitoring the health of both the pregnant individual and the baby. Healthcare providers assess various factors throughout pregnancy, including fetal growth and maternal health indicators, to identify any potential concerns. Open communication with one’s healthcare team is important for discussing any symptoms or worries.
Monitoring fetal movement, often referred to as “kick counts,” is a simple yet effective way for expectant parents to observe their baby’s well-being. A noticeable decrease in fetal movement or the absence of movement should prompt immediate contact with a healthcare provider. They can assess the situation and recommend further evaluation if needed.
Discussions about delivery timing with a healthcare professional become increasingly relevant as a pregnancy approaches and passes its due date. Healthcare providers weigh the slight increase in stillbirth risk with advancing gestation against the risks associated with induction of labor. These decisions are highly individualized, taking into account the specific circumstances of each pregnancy and the preferences of the expectant parent.