Stillbirth Basics

How common is stillbirth?

In the United States, stillbirth happens in about one out of every 175 deliveries, or approximately 21,000 pregnancies yearly.

What is the difference between a miscarriage and a stillbirth?

Miscarriage and stillbirth both describe types of pregnancy loss. Stillbirth is the death of a fetus at or after 20 weeks of pregnancy. If a pregnancy loss occurs before 20 weeks, doctors consider it a miscarriage.

Healthcare providers further classify stillbirth as early, late, or term.

  • An early stillbirth is a fetal death between 20 and 27 completed weeks of pregnancy.
  • A late stillbirth occurs between 28 and 36 completed pregnancy weeks.
  • A term stillbirth occurs between 37 or more completed pregnancy weeks.
What are the most common causes of stillbirth?

Fetal growth restriction or problems with the placenta (called placental insufficiency) are thought to cause about 30 percent of stillbirths (one out of every three). The placenta carries blood, oxygen, and nutrition to the growing fetus. Anything that threatens how the placenta works, therefore, threatens the pregnancy. Infections, inflammation, and decreased blood flow can also cause stillbirth.

Abnormalities in the fetus (birth defects or congenital anomalies) or abnormalities in the fetal genome are thought to cause about 20 percent of stillbirths (2 out of every 10). Fetal infections, placental abruption, and umbilical cord complications are less common causes of stillbirth, comprising an additional 10 percent each. Placental abruption occurs when the placenta separates from the uterine wall before delivery. Other less common causes of stillbirth are:

  1. Preeclampsia – a severe blood pressure complication of pregnancy
  2. Fetal-maternal hemorrhage – happens when fetal blood enters the mother's bloodstream during pregnancy, can happen spontaneously or as a result of trauma and injury)
  3. Twin-to-twin transfusion – unbalanced blood flow between identical twins sharing the same placenta.

The cause of many stillbirths (one out of every three) can not be identified or may be caused by multiple risk factors.

What are the risk factors for stillbirth?

The risk of stillbirth varies depending on where you live, your age, race, and other medical conditions. Some risk factors are modifiable (like smoking cigarettes during pregnancy), and others are non-modifiable (like race). In developed countries, the most common risk factors associated with stillbirth are:

  • Being a non-Hispanic black person
  • Never having been pregnant previously (nulliparity)
  • Advanced maternal age (older than 35 years)
  • Obesity (BMI greater than 30)
  • Having pre-existing diabetes
  • Chronic (pre-pregnancy) hypertension (high blood pressure) or hypertension during pregnancy only 
  • Smoking
  • Alcohol use
  • Having used assisted reproductive technology (infertility treatment) to become pregnant 
  • Multiple gestations (twins, triplets)
  • Male fetal sex
  • Unmarried status
  • Prior pregnancy complications 

There may also be more than one reason for stillbirth. Researchers estimate that problems with a fetus’s genetic information (called the genome) may cause somewhere between six to 13 out of every 100 stillbirths.


What is genomics?

Genomics is the study of a person’s genes, collectively called the genome. Billions of cells make up our bodies. Inside these cells are structures called chromosomes, which carry DNA.

Genes are building blocks of genetic information, units of DNA, carrying instructions for making a specific protein or set of proteins. Like a phone or computer's operating system, the genome directs how the body works. Each of the estimated 25,000 genes in the human genome codes for an average of three proteins (NIH).

Each gene consists of two twisting, paired strands (called a double helix) of microscopic (not visible to the human eye) DNA molecules. DNA stands for Deoxyribonucleic acid. Four chemical units, adenine (A), thymine (T), guanine (G), and cytosine are the building blocks of DNA. Combining these letters spells out or tells our body how to make proteins that affect our growth and development.

Genomics is the field of study, learning how to read the sequence of DNA to understand better how our genes keep us healthy.

How do genes influence stillbirth, pregnancy loss, and birth defects?

If there is a change (sometimes called a genetic mutation) in a baby’s DNA, it may have problems growing and developing. Such changes might lead to miscarriage, stillbirth, or abnormalities in the way the body grows (seen as birth defects).

A baby’s cells contain DNA inherited from each parent. Sometimes, DNA variations can be inherited (passed on) from a parent, even if that parent is entirely healthy. Sometimes, changes in DNA develop just before or just after conception and are not present in either parent.

Genetic variations or mutations can be big or small. Some changes do not affect the baby at all, other changes are more significant.  Changes can involve many errors in the arrangement of the DNA at multiple different locations or only affect a single gene. Some of these genetic variations will cause visible changes in the fetus and cause birth defects (also called congenital disabilities). Other genetic variations do not change the fetus’s appearance. Genetic testing may be the only way to detect such genetic changes or mutations. Fetal genetic testing looks for changes in a baby’s DNA.

Stillbirth and pregnancy loss may be more likely depending on which genes are impacted and how many variations there are. Current research suggests that changes in the baby’s genome may explain up to 20 percent of stillbirths.

What is fetal genetic testing?

Fetal genetic testing examines a fetus's DNA and chromosomes. Chromosomes are structures made from twisted strands of proteins called DNA. After your healthcare provider diagnoses a stillbirth, they may recommend two types of genetic testing:

  1. Chromosomal microarray (CMA) looks for segments of DNA that are added or subtracted from the total DNA in a baby’s body. Having too much or too little DNA can harm how a baby grows and develops. These variations could cause a stillbirth.
  2. Whole genome sequencing (WGS) looks at the actual letters that make up the DNA (A, G, T, C) in the baby’s cells in the body to see if the “spelling” is correct or not. Even one incorrect letter within the DNA can be enough to cause a stillbirth if it affects a very important piece of DNA.
  3. Whole exome sequencing (WES) is a shortened version of WGS testing described above. Instead of sequencing the fetus’s entire genome, this screen only looks at the exome. The exome is the name given to all of the exons in DNA. Exons are the portion of DNA that contain instructions for making proteins. This is thought to be the most important part of the human DNA. The exome is about 1 percent of a person’s genome, so whole exome sequencing is a shorter version of whole genome sequencing that can still provide valuable information about the possible cause of stillbirth, fetal loss, or structural anomalies.

What testing should birth parents have after stillbirth or as part of participating in this study?

Collecting a maternal blood sample is a standard part of any stillbirth workup. This informs healthcare providers about past or recent infections, differences in blood type between mom and baby, autoimmune disorders, diabetes, thyroid disease, substances that can affect the baby’s development, or other maternal health conditions. Testing is most often completed before delivery, but it can also happen after delivery.

The additional testing offered through this study involves collecting samples (blood or saliva) from the birth parents for genetic analysis. The samples taken from the birthing parents help researchers to interpret information about the baby’s genetics. Genetic tests can be done on the baby without parental samples, but it is much more difficult to interpret the results without them.

What is fetal phenotyping?

Fetal phenotype refers to all of the observable physical characteristics of a baby. These are influenced by the genotype (code of DNA) and also the environment. For example, a baby could be small because its parents are small (the genetic part) or it could be small because it did not get enough nutrients due to an issue with the placenta or the cord (environment) during pregnancy. Often phenotype is due to a combination of both factors.

There are several ways to study fetal phenotype. In the case of a stillbirth, collecting information about observable characteristics of the fetus can provide clues about the possible cause of the stillbirth. ACOG recommends evaluating all stillbirths with:

  1. Prenatal ultrasound before stillbirth delivery.
  2. A fetal autopsy (with your consent).
  3. An examination of the placenta.
  4. An examination of the umbilical cord.
  5. An examination of the membranes (amniotic sac).

An exam of the baby at birth can provide information about potential causes of stillbirth, such as differences in the umbilical cord or the baby’s anatomy that sometimes cannot be seen on ultrasound.  Even if mothers had detailed ultrasound scans during pregnancy, this type of exam is still important.

Specially-trained healthcare providers called pathologists perform these examinations, timed as close as possible to the time of delivery. Pathologists look both outside and inside the baby. From the outside, they measure the baby, look for specific abnormalities of the face, arms, legs, and palms, and potentially conduct X-rays to look for other skeletal changes.

For the internal part of the autopsy exam, the pathologist makes surgical incisions in the chest, abdomen, and back of the skull. In general, all organs are returned to the baby’s body, though small samples may be removed for further investigation if

necessary (and if you give your permission).

An autopsy can be done in a “partial” way if you prefer. This means you can “opt-out” of certain parts of the exam and exclude certain areas of the body.

Having a fetal autopsy after a stillbirth is considered one of the most important parts of a stillbirth workup and can identify the cause of a stillbirth in about 4 out of every ten stillbirths (42 percent).

Examining the placenta can help identify the cause of stillbirth in two-thirds of stillbirths. Having trained pathologists examine the placenta and umbilical cord can provide essential clues about the possible cause of stillbirth. A pathologist can look at different placenta and umbilical cord measurements, including areas that may show signs of blood clots or other damage.

If you are uncomfortable with an autopsy, other types of imaging like X-ray, magnetic resonance imaging (MRI), or computed tomography (CT scan) may be able to provide more information about what might have caused your stillbirth. These are not as likely to provide an answer but can help in certain situations. 

Talk with your healthcare provider about what feels right for you. If your provider does not offer you an autopsy or these other types of fetal phenotyping, you can ask for them.

What is the history of genetic testing for stillbirth?

Genetic testing for stillbirth has undergone several changes in the past decade. Early genetic testing options frequently included a karyotype. A karyotype is a laboratory-produced image of a person’s chromosomes isolated from an individual cell and arranged in numerical order. Chromosomes are the structures holding DNA and genetic information. A karyotype’s disadvantage is that it can only see very large pieces of missing or extra information within chromosomes.

Chromosomal microarray (CMA) is the type of genetic test used more commonly today. CMA identifies small (and large) changes that may contribute to a stillbirth. Both karyotype and microarray are done through amniocentesis – a procedure to remove amniotic fluid and cells from your uterus for testing. In some cases, direct testing of tissue, like placenta or fetal biopsy, can provide cells for CMA.

The International Fetal Genomics Consortium is studying a type of genetic testing that detects even smaller changes in the genetic code. These technologies are called whole exome and whole genome sequencing. This test requires the same samples used in a CMA but allows the laboratory to detect changes more minor than those seen on a microarray.


What support resources can I access after a stillbirth? 

In this website's “Find Support” section, we have assembled a list of books, support groups, organizations, and online resources to provide comfort, information, and assistance for people impacted by fetal loss, stillbirth, or genetic diagnoses.

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