In the United States, stillbirth is defined as a pregnancy that terminates at 20 weeks gestation or more. According to "The Journal of Maternal-Fetal and Neonatal Medicine," in the United States, stillbirths occur in about 1 percent of all births (or 7 per 1000). Associated maternal risk factors such as cigarette use, diabetes, low socio-economic factors, prior stillbirth, Rh disease and advanced maternal age can contribute to stillbirth, according to the International Stillbirth Alliance. Investigation via fetal autopsy and examination of the placenta (afterbirth) to determine the cause of stillbirth is valuable for identifying preventive strategies and for counseling parents regarding future pregnancies.
Congenital Abnormalities
Malformations of the heart, lungs, brain, liver, kidneys and/or limbs; chromosomal abnormalities; and metabolic disorders are causes of fetal death. Often there are multiple structural abnormalities present.
Placental Detachment
When the placenta prematurely separates from the womb (uterus), the fetus is deprived of oxygen and death occurs. This may result from the failure of the placenta to attach to a region of the womb where the placenta can sustain the fetus as it grows. Maternal cigarette use and hypertension are risk factors associated with this cause.
Maternal/Fetus Infection
Identification of maternal/fetus infection may be made through histological examination of the placenta and/or fetus. Some infections are also found with evidence of fetal oxygen deprivation; it may be difficult to determine whether the infection alone produces the stillbirth, or whether the infection contributes to placental damage that produces the stillbirth. Infection associated with rubella can produce congenital abnormalities. Parvovirus, influenza, high maternal fever, maternal malaria, polio, syphilis and Lyme disease can be identified as contributing to stillbirth.
Umbilical Cord Accident
Injury to the umbilical cord disrupts blood flow to the fetus and can cause stillbirth. Sometimes a true knot develops in the cord and decreases fetal blood flow and consequent oxygen deprivation (hypoxia). The umbilical cord may descend (prolapse) outside of the birth canal and become compressed or open to infection. If premature rupture of membranes (PROM) occurs, premature labor may begin. In the case of identical twins (two fetuses with one placenta), one fetus could become entangled in an umbilical cord.
Medical Illnesses
Maternal medical conditions associated with stillbirth include thyroid disorders, hypertension and pre-eclampsia, lupus, diabetes mellitus, obesity and chronic renal disease. Aggressive management of these diseases has resulted in a reduction in stillbirth rates. The danger still remains for those with undiagnosed disease such as diabetes or hypertension.
Fetal Brain Injury
Further exploration into fetal brain injury as a cause of stillbirth is indicated by pathological examination findings of brain lesions found in the brain stem and spinal cord. Such lesions can cause central nervous system deformation, contributing to stillbirth.
References
- "The Journal of Maternal-Fetal and Neonatal Medicine: Stillbirth: A Review"; R.L. Goldenberg et al; 16:79-87, 2004
- International Stillbirth Alliance: Causes
