Special Feature
Prevention of Antepartum Fetal Deaths
By Steven Gabbe, MD
With the near elimination of intrapartum fetal deaths, stillbirths occurring prior to the onset of labor represent approximately half of all perinatal deaths in the United States. This article will review the major causes of antepartum fetal deaths, describe the contributions of specific high-risk complications to these perinatal losses, and propose strategies for the prevention of antepartum fetal deaths.
The perinatal mortality rate (PMR) is defined as the number of late fetal deaths (those occurring at 28 weeks gestation or later) plus early neonatal deaths (those occurring from birth to 6 days of age) per 1000 live births plus fetal deaths. In 1993, the National Center for Health Statistics (NCHS) reported the PMR in the United States to be 9.1/1000, with neonatal deaths contributing 5.3/1000 and fetal deaths 3.8/1000. The definition of PMR used by the NCHS is not uniformly applied. The American College of Obstetricians and Gynecologists (ACOG) and most investigators in this field use a birthweight of 500 g rather than 28 weeks gestation or more to define fetal deaths. Nearly half of all fetal deaths occur before 28 weeks gestation, and, in fact, only 20% occur at term. Therefore, using the more widely applied ACOG criteria will include more fetal deaths and raise the PMR. By this definition, the PMR in the United States in 1994 was approximately 12/1000, with fetal deaths comprising more than half of all perinatal losses. Clearly, it is important to examine the definition used for fetal deaths whenever reviewing data on this subject.
Because fetal deaths are relatively uncommon, large population studies must be conducted to determine changes in the cause of stillbirths. Fretts and colleagues at the Royal Victoria Hospital in Montreal have carefully examined the etiology of fetal deaths in nearly 95,000 births with weights of 500 g or more between 1961 and 1993.1-3 They report a decline of 70% in the fetal death rate during this 30-year (and more) period with a fall from 11.5/1000 in the 1960s to 3.2 in 1990-1993. They attribute this significant reduction in fetal deaths to: 1) prevention of Rh sensitization; 2) improved antepartum and intrapartum surveillance; 3) improved detection of intrauterine growth restriction (IUGR); 4) improved recognition of fetal anomalies with ultrasound; and 5) improved care of maternal diabetes mellitus and pre-eclampsia. Examination of specific causes of fetal death revealed that unexplained antepartum deaths, defined as "death of an appropriate for gestational age fetus before labor with no evident fetal, maternal, or placental abnormality (with or without cord loops)," remained the single largest group of stillbirths, despite an autopsy rate of more than 95%. Fetal deaths due to abruption were the second largest group and nearly doubled during the study period-probably due to cocaine abuse. IUGR remained the third most important group of fetal deaths and, in many cases, was not recognized prior to the loss. Other major causes of stillbirth were lethal anomalies and infection, which included intrauterine deaths due to preterm rupture of the membranes with choriamnionitis as well as other infectious etiologies such as syphilis and listeria. Table 1 provides a summary of the etiology of fetal deaths.
Table 1
Etiology of Fetal Deaths
Asphyxia
(IUGR, prolonged gestation) 30%
Maternal Complications
(abruption, hypertension, diabetes) 30%
Unexplained
(fetal-maternal hemorrhage) 20%
Malformations
(chromosomal abnormalities) 15%
Infectio 5%
Advanced maternal age has emerged as an important risk factor for intrauterine fetal death in several studies. Fretts reported that, even after correcting for diabetes mellitus, hypertension, and chromosomal abnormalities, the fetal death rate was nearly doubled in women 35 years or older. Advanced maternal age was associated with a significantly higher risk of unexplained fetal death when compared with younger women. The etiology for the higher fetal death rate in pregnancies complicated by advanced maternal age has not been determined. A list of strategies to reduce antepartum fetal deaths is presented in Table 2.
Table 2
Strategies to Reduce Antepartum Fetal Deaths
· Determination of the cause of fetal death
· Antepartum fetal evaluation in all pregnancies with routine fetal movement counting
· Surveillance for fetal malformations in all pregnancies with a triple screen and routine ultrasound at 18-20 weeks
· Surveillance for detection of IUGR with fundal height measurements and ultrasound at 30-32 weeks in high-risk patients and patients with lagging growth
· Programs to identify and treat cocaine abuse in pregnancy
First, it is important to determine the cause of a fetal death so that the patient and her partner can be counseled, the risk of recurrence described, and a plan of care for subsequent pregnancies developed. The obstetrician who delivers a stillborn infant should write a detailed note describing the fetus, amniotic fluid, umbilical cord, placenta, and membranes. If the infant is malformed, growth restricted, or hydropic, chromosomal studies should be obtained. An autopsy should be requested. Tests for syphilis, antiphospholipid antibodies and lupus anticoagulant, and, if the patient has not been screened for diabetes mellitus during gestation, a fasting glucose should be ordered. Because significant fetal-maternal hemorrhage has been observed in approximately 5% of all fetal deaths, a Kleihauer-Betke test should be obtained. To prevent antepartum deaths, routine fetal movement counting should be considered in all pregnancies starting at 28 weeks gestation. The modified count-to-ten method developed by Moore and Piacquadio is a simple and valuable technique.4 Patients begin counting in the evening and record the time it takes to feel 10 movements. If they have not had 10 movements in two hours, they are instructed to contact their healthcare provider. It would also seem appropriate to initiate twice weekly non-stress testing in women 35 years or older or more late in the third trimester-perhaps at 34-36 weeks. To reduce fetal deaths resulting from fetal malformations, a triple analyte screen should be offered and routine ultrasound performed at 18-20 weeks. To detect IUGR, careful, serial measurements of fundal height should be performed with an ultrasound examination at 30-32 weeks in high-risk patients including those with vascular disease and in patients with lagging uterine growth. Finally, patients who are known to be abusing cocaine should be counseled and directed toward treatment programs.
References
1. Fretts RC, Obstet Gynecol 1992;79:35-39.
2. Fretts RC, N Engl J Med 1995;333:953-957.
3. Fretts RC, Usher RH. Obstet Gynecol 1997;89(1): 40-45.
4. Moore TR, Piacquadio K. Am J Obstet Gynecol 1989;160:1075.
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