Embryo and Fetal Pathology
Intrauterine fetal death during the late second or third trimester of pregnancy is reported to occur once in every 100 births. Although the risk is less with improved fetal surveillance and testing, a stillbirth remains an alarming event to both the parents-to-be and the physician, requiring thorough investigation for proper patient counseling. After delivery, obvious abnormalities are uncommon on gross inspection of the fetus or placenta. The clinical history is often unremarkable, and any preexisting antepartum medical or obstetric complications may not relate directly to the cause of the stillbirth. Therefore, the cause is often subtle and frequently bewildering to the parents.
In 25 percent of stillbirths, there is a fetal abnormality. One half of these have a single-gene, chromosomal, or polygenic cause with a risk for recurrence. In approximately twothirds, the recurrence risk is greater than 1 percent. In 25 %, the recurrence risk is greater than 10 percent. Prenatal diagnosis is possible in 50 percent of those cases where there is a risk of recurrence.
Current recommendations for evaluation of all stillbirths and infants dying within 24 hours after birth (neonatal deaths) include gross and microscopic autopsy of the fetus and the placenta, postmortem photography and radiography, analysis of bacterial cultures, karyotyping of the fetal tissues, and saving tissue for DNA studies when indicated
Detailed clinical examination of the placenta will reveal abnormalities in more than 80 percent of cases, autopsy examination of the placenta will reveal abnormalities in 70 percent of cases and placental histological evaluation will reveal abnormalities in 98 percent of cases. The placental abnormalities are the sole findings in 10 percent of cases. The most frequent placental anomalies are haemorrhagic endovasculitis, severe acute chorioam-nionitis, retroplacental hematomas, erythroblastosis/hydrops, and villus changes indicative of uteroplacental vascular insufficiency. Certain abnormalities of the umbilical cord may be best appreciated histologically.
A two-vessel cord, which may be associated with underlying congenital anomalies, may go undetected without microscopic examination.
Often the single most useful tool for establishing a specific diagnosis is the gross postmortem examination. Careful and complete histopatho-logical evaluation may further understanding of the mechanisms of embryogenesis, pregnancy loss, and early neonatal mortality in addition to providing a specific diagnosis in an isolated case. Since full details of specific organ weights proportional to total fetal body weight at varying gestational ages are not widely available, the data are provided here (Figs. 16.2-16.9).
Figure 16.1 Protocol for selective evaluation of stillbirths and early neonatal deaths. From Mueller et al. (1983), by permission.
All stillbirths/neonatal deaths Family history Obstetric history Photographs/x-ray film Bacterial cultures Gross autopsy
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