In the United States, the term stillbirth or fetal demise does not have a standard definition.
For statistical purposes, fetal losses are classified according to gestational age. A death that occurs prior to 20 weeks' gestation is usually classified as a spontaneous abortion; those occurring after 20 weeks constitute a fetal demise or stillbirth. Many states use a fetal weight of 350 g or more to define a fetal demise.
Although this definition of fetal death is the most frequently used in medical literature, it is by no means the only definition in use. Even within the United States, the differences in the definitions used are substantial.
In addition, not all states interpret the weeks of gestation in the same manner. In California, 20 weeks' gestation is worded "twenty utero gestational weeks" and has therefore been interpreted to be 23 weeks from the last menstrual period. (Implantation in the uterus does not occur until 1 wk after fertilization.) Physicians must check the reporting requirements for the state(s) in which they practice.
Frequency of Fetal Death
In 2010, the estimated global number of stillbirths was 2.64 million (uncertainty range, 2.14-3.82 million). The worldwide stillbirth rate declined by 14.5% from 22.1 stillbirths per 1000 births in 1995 to 18.9 stillbirths per 1000 births in 2010.
Causes of Fetal Death
The etiology of fetal demise is unknown in 25-60% of all cases. In cases where a cause is clearly identified, the cause of fetal death can be attributable to fetal, maternal, or placental pathology. One prospective study attributed 64.9% of fetal death to placental pathology overall. The same study noted higher rates of fetal demise secondary to placental pathology at late gestational age.
A meta-analysis of 96 population-based studies found that maternal overweight and obesity was the highest-ranking modifiable risk factor for stillbirth. Advanced maternal age (>35 y) and maternal smoking were also significant. Small size for gestational age and abruption were the highest-ranking pregnancy disorder risk factors for stillbirth. Preexisting diabetes and hypertension are also important contributors to stillbirth.
- Prolonged pregnancy (>42 wk)
- Diabetes (poorly controlled)
- Systemic lupus erythematosus
- Antiphospholipid syndrome
- Advanced maternal age
- Rh disease
- Uterine rupture
- Maternal trauma or death
- Inherited thrombophilias
- Multiple gestations
- Intrauterine growth restriction
- Congenital abnormality
- Genetic abnormality
- Infection (ie, parvovirus B19, CMV, Listeria)
- Cord accident
- Premature rupture of membranes
- Vasa previa
- Fetomaternal hemorrhage
- Placental insufficiency
- Risk factors (weak predictive value)
- African American race
- Advanced maternal age
- History of fetal demise
- Maternal infertility
- History of small for gestational age infant
- Small for gestational age infant
- Paternal age
Evaluation of Fetal Demise
Up to 60% of stillbirths have no identifiable etiology. Attempting to determine the cause of fetal death remains important because it may influence estimates of recurrence and future preconceptional counseling, pregnancy management, prenatal diagnostic procedures, and neonatal management.
Many institutions use a selective workup based on clinical findings. For example, when clinical findings strongly suggest a cause for the fetal demise at Santa Clara Valley Medical Center, either no further testing or limited testing is performed. Causes deemed fairly obvious include cord accident (ie, prolapse, entanglement, true knot, tight nuchal cord), anencephaly, or previously known lethal karyotype. In such cases, no further workup is necessary.
If severe clinical abruption is present, testing can be limited to toxicology screening and possibly a thrombophilia workup.
The most important part of the workup of a fetal demise is the autopsy of the fetus. The decision to proceed with an autopsy must be made by the parents and informed consent is necessary. With parents who are resistant to the idea of a complete autopsy, a limited fetal evaluation should be discussed with the family. Although uncommon, postmortem MRIs can provide valuable information in the evaluation of a fetus when an autopsy cannot be performed.
The placenta and the membranes should be carefully examined, including cultures. Again, an algorithm or checklist is helpful to avoid omissions (see image below). This inspection is even more important if the family declines an autopsy.
This is an example of a checklist to be used following fetal death. Courtesy of Santa Clara Valley Medical Center.
Fetal karyotype can be obtained from a sample of amniotic fluid (preferred), fetal blood, or fetal tissue (skin or fascia lata). Fetal karyotype should be considered in all cases. It is especially important if the fetus is dysmorphic, has growth retardation, is hydropic, or has anomalies or other signs of chromosomal abnormality. Chromosomal analysis should also be considered in patients with multiple pregnancy losses, especially with a history of second- and third-trimester losses or when a parent has a balanced translocation or mosaic chromosomal pattern. Many authorities (including the ACOG committee on evaluation of stillbirth) recommend obtaining this test in every fetal demise.
A summary of the protocol for the fetus and placenta is as follows:
- Careful inspection
- Placental cultures for suspected listeria infection (To obtain placental cultures, separate the amnion and the chorion and submit a culture specimen using Stuart media.)
- Radiographs, if indicated
- MRI, if no autopsy
- Fetal karyotype
- Maternal Studies
- Maternal studies that should also be considered during the workup of a fetal demise include the following:
- Diabetes testing using hemoglobin A1C and a fasting blood glucose
- Syphilis screening using the VDRL or rapid plasma reagent test
- Thyroid function testing (ie, TSH, FT4)
- Urine toxicology screening
The above tests have traditionally been a part of an evaluation for the etiology of fetal demise. If diabetes screening has been performed during the prenatal period, repeat testing for diabetes is probably not necessary. Similarly, if the patient has no signs or symptoms of thyroid disease, thyroid dysfunction is unlikely to be the cause of the demise. However, these tests are inexpensive and normal results may be reassuring to the patient.
- Additional tests that should be considered are as follows:
- Antibody screening
- CBC count with platelet count
- Kleihauer-Betke test
- Infection: See Bacterial Infections and Pregnancy. Infection is a cause of fetal demise. The frequency is higher in developing countries. Autopsy and histologic evaluation of the placenta is probably the best way to document an infectious etiology for a fetal demise.
Authority opinions vary as to which panel of tests is appropriate. Traditionally, most authorities have recommended obtaining TORCH (toxoplasmosis, rubella, cytomegalovirus, and herpes simplex virus) antibody titers. In reality, this is rarely helpful in the diagnosis. In addition, it is questionable whether cytomegalovirus virus causes fetal demise. If no obvious cause for the demise is established or if clinical signs or symptoms suggest infection, consider testing for (1) cytomegalovirus (acute and chronic titers), (2) rubella virus (acute and chronic titers, if not immune), (3) parvovirus (acute and chronic titers), and (4) Toxoplasmosis gondii (acute and chronic titers) and (5) syphilis. A more cost-effective approach is to limit testing for cytomegalovirus, rubella virus, and T gondii to those patients in whom clinical findings suggest the possibility of intrauterine infection (ie, those with intrauterine growth restriction, microcephaly).
Testing for Fetal Demise
The following provides a summary of the current status of testing for fetal demise. This is adopted with permission from the work of Dr. Robert M. Silver and the Stillbirth Collaborative Research Network. This summary has been modified as more recent studies have become available.
- Commonly accepted tests
- Fetal autopsy
- Placental evaluation
- Indirect Coombs test
- Serologic test for syphilis
- Testing for fetal-maternal hemorrhage (Kleihauer-Betke or other)
- Urine toxicology screen
- Parvovirus serology
- Lupus anticoagulant, for antiphospholipid testing
- Anticardiolipin anticoagulant, for antiphospholipid testing
- Anti-B 2 -glycoprotein 1 IgG or IgM antibodies
- Useful in some circumstances
- Factor V Leiden
- Prothrombin mutatio
- Protein C, protein S, and antithrombin III deficiency
- Hemoglobin A1C
- TORCH titers
- Placental cultures
- Testing for other thrombophilias
- Developing technology
- Comparative genomic hybridization
- Testing for confined placental mosaicism
- Nucleic acid-based testing for infection
Management of Future Pregnancy
Fetal death of unknown cause is a special problem. Because a large number of etiologies of fetal demise exist, a provider has difficulty determining risk of stillbirth for any particular pregnancy. Evidence-based models such as Active Management of Risk In Pregnancy At Term (AMOR-IPAT) are being created in an effort to better estimate this risk. Although recurrent fetal loss is uncommon, patients are naturally anxious. Most patients find increased fetal surveillance with the next pregnancy reassuring, even though such testing is not clearly beneficial. The ACOG recommends antepartum testing starting at 32-34 weeks' gestation in an otherwise healthy mother with history of stillbirth. Weekly biophysical profile or fetal heart rate testing can be combined with maternal kick counts in the third trimester. For patients who have experienced earlier loss, frequent ultrasound is reassuring.
Optimal management of chronic medical conditions is important prior to the next pregnancy.