Introduction
The expectation of every pregnancy is that a healthy patient and baby will be the outcome. Unfortunately, we know all too well that this is not always the case. One of the most devastating situations is when fetal death occurs. Fortunately, the occurrence of fetal death is rare in the United States. The most recent statistics demonstrate a fetal death rate of 7/1000 total births. While there is still no standard that is applied universally, the definition most commonly used for fetal death or stillbirth, including the American College of Obstetricians and Gynecologists, is when a fetus that weighs 500 g or more or has attained a gestational age of 20 weeks or greater is delivered without any signs of life (Apgar scores 0,0).
Fetal mortality rates over the last several decades have decreased significantly in the United States. In 1950, the fetal death rate was approximately 18/1000 total births. Since then, we have seen a steady decline in the rate of stillbirths. Many factors have contributed to this decrease. Probably, the most obvious is the improvement in obstetric care. The implementation of antenatal testing for high-risk patients has also resulted in fewer stillbirths. The almost universal application of ultrasound and increased ability to diagnose fetal chromosomal and congenital anomalies have resulted in elective termination of fetuses that would likely result in stillbirth. Lastly, as neonatal care has improved, many fetuses that would have potentially expired in utero are delivered at earlier gestations. Thus, an increase in iatrogenic early preterm deliveries has evolved.
Benefits of fetal death evaluation
As stated earlier, when a stillbirth occurs it is often devastating to the parents, family, and caregivers. While it is clear that nothing can be done to prevent a stillbirth after it has occurred, there is a great deal of benefit that can be obtained by performing a thorough evaluation in hopes of identifying reasons why the fetal death happened. While it is very difficult to state definitively that a specific circumstance or condition caused the fetal death, a comprehensive stillbirth evaluation will at least allow one to identify potential associations.
Probably the most practical and important benefit of performing a complete evaluation is to help with parental grieving and the parental right to know. Almost invariably there is a sense of guilt that is felt by the mother. What did I do wrong? How could I have prevented this from happening? The parents have a strong desire, and deserve, to obtain information that will help them understand why this happened, and whether it may happen again. The answers will often assist and influence their reproductive decision-making.
A thorough stillbirth evaluation will also assist the physician with prenatal assessment, intervention, and management in future pregnancies. For example, if a patient had a prior stillbirth associated with anencephaly, she would best be served by undergoing genetic counseling and ultrasound evaluation. On the other hand, if a patient had a prior stillbirth that was associated with poorly controlled diabetes mellitus, she would best benefit from preconception counseling and obtaining good glycemic control before becoming pregnant.
Stillbirth evaluation is also important and beneficial to the physician in helping to decrease inappropriate litigation. When fetal death occurs it is not uncommon for the physician to be blamed. Sentiments such as “The doctor should have known something was wrong” or “The doctor must have missed something” are common after fetal death. Very often a comprehensive evaluation will demonstrate that the physician was not at fault, and that the fetal death could not have been prevented.
Lastly, studying fetal death has increased scientific understanding of the causes of stillbirth. This has allowed us to identify patients who might be at risk for stillbirth, and has assisted with a variety of interventions to help minimize this risk.
The causes of fetal death are many and varied. Early reports in the literature centered primarily on maternal medical conditions. Very little information was available regarding the association of fetal abnormalities and placental abnormalities with fetal death. Consequently, a large percentage of stillbirths were classified as unexplained. However, as we have gained a greater understanding of fetal abnormalities through ultrasound and autopsy, and have become more proficient at examining the placenta for specific abnormalities, the number of unexplained stillbirths has decreased.
In 1997 a review of causes of fetal death was published. By this time, greater emphasis was placed on the importance of autopsy and placental pathology. In addition, antepartum testing was being performed almost uniformly for maternal medical conditions such as chronic hypertension and pregestational diabetes. As a result, this review seemed to de-emphasize maternal conditions as a separate cause of fetal deaths, comprising only 5–10%. Instead, intrinsic fetal anomalies were noted as being associated with fetal death and 25–40% of stillbirths were attributed to fetal causes. These were broken down as follows: 6–13% chromosomal, 10–17% non-chromosomal, 10% nonimmune hydrops, and 5–12% fetal infections. Placental abnormalities were identified as the cause 25–35% of the time. Therefore, the percentage of unexplained stillbirths had decreased to 25–35%.
A variety of demographic factors have been associated with fetal death. Advanced maternal age of 35 years or more doubles the risk. Obesity is also a known risk factor and women weighing 85 kg or more (BMI ≥30 kg/m2) have a 2–3-fold increase in fetal death. African American women have a stillbirth risk 1.5 times that of Caucasian women, and smokers also have an increased risk of fetal death compared to nonsmokers. Thus, there are some demographic risk factors that can be potentially modified.
Several maternal medical diseases are associated with increased fetal death rates (see table 18.1). In addition, increased fetal death rates have been observed in patients with underlying thrombophilias. These can be either inherited (antithrombin deficiency, protein C deficiency, protein S deficiency, factor V Leiden mutation, prothrombin gene mutation or methylene tetrahydrofolate reductase deficiency) or acquired thrombophilias, in which lupus anticoagulant, anticardiolipin antibodies or anti-β2 glycoprotein antibodies are present.
Table 18.1 Maternal medical diseases
| Condition | Estimated stillbirth rate |
| All pregnancies | 6–7/1000 |
| Chronic hypertension | 5–25/1000 |
| Severe preeclampsia | 21/1000 |
| HELLP syndrome | 51/1000 |
| Gestational diabetes | 5–10/1000 |
| Type 1 diabetes | 6–10/1000 |
| Type 2 diabetes | 6–20/1000 |
| SLE | 40–150/1000 |
| Intrahepatic cholestasis | 12–30/1000 |
Simpson LL. Semin Perinatol 2002; 26: 42–50
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