also concluded that CAS occurring before 24 weeks gestation was associated with a significantly higher rate of stillbirths . The aforementioned study by Bibbo et al . is in agreement with a literature review of 47 case reports that demonstrated a 40 % rate of preterm birth in pregnancies complicated by CAS . 4
Determining the potential etiology of CAS is helpful in planning the management strategy for the pregnancy . Two of the more detailed descriptive causes of CAS are those of iatrogenic origin and those associated with fetal chromosomal abnormalities . A retrospective chart review of 75 fetal surgery cases determined that the incidence of CAS following the procedures was 47 %, with more invasive procedures having higher indicence of CAS . 5 In regard to fetal chromosomal abnormalities , a prospective study completed by Ulm et al . found that 12 % of their patients ( N = 492 ) between 14 and 18 weeks of gestation at high risk for aneuploidy had unfused chorion and amnion . 6 Likewise , mothers with unfused chorion and amnion who were identified as being of advanced maternal age , without any other abnormalities found on ultrasound , had a 4 % incidence of aneuploidy . 6 After ultrasound diagnosis of CAS and appropriately counseling patients regarding potential risks , treatment strategies are gestational age dependent and range from increased fetal and maternal surveillance to delivery .
CONCLUSION
While placental abruption is a known complication of abdominal trauma , our case is unique in that the presumed abruption was diagnosed with no immediate ultrasound abnormalities for the first four days following an MVC . Delayed complete CAS was not demonstrated by ultrasound until sonography was performed nine days after the MVC . While other mechanisms for CAS have been described , obstetricians should be aware that pregnant patients who undergo abdominal trauma , as experienced in a MVC , may develop delayed CAS . In the third trimester , follow-up with twice-weekly biophysical profiles and sonographic estimation of fetal growth every four weeks is prudent to detect and treat the delayed CAS in a timely manner .
IMAGE 1
Complete separation of the amnion and chorion . Yellow arrows indicate amnion ; blue arrow indicates chorion .
IMAGE 2
Complete separation of the amnion and chorion . Yellow arrows indicate amnion ; blue arrow indicates chorion ; red arrow indicates fetal leg inside amniotic cavity .
West Virginia Medical Journal • September 2022 • 39