Fender-benders can be deadly for a fetus, according to several studies discussed in an article by Sherry Boschert. Even minor trauma, including low-speed car accidents and falls, can lead to placental abruption. The condition causes the placental lining to separate from the uterus and can cause maternal and fetal death.
Crash testing using “pregnant” dummies and computer modeling shows that “a frontal impact first throws the uterus forward against the abdominal wall,” and then the torso flexes forward and crushes the uterus between the torso and the knees. “All this creates a high degree of negative pressure in the back of the uterus that can pull the placenta off the uterine wall,” according to Dr. William G. Barson in Boschert’s article.
Symptoms of placental abruption vary and may include vaginal bleeding, contractions, abdominal tenderness, and decreased fetal movement. Though vaginal bleeding is typical in most cases, 20% of abruptions are associated with a concealed bleeding because the blood collects behind the placenta and is undetectable without internal observation. In the absence of vaginal bleeding—especially after the patient has experienced some minor trauma—contractions and uterine tenderness are revealing signs of placental abruption.
Abdominal trauma is a major risk for placental abruption, and commonly occurs during even gentle motor vehicle accidents. Lower seat belts should always be worn across the pelvis, never over the abdomen. Pregnant women involved in auto crashes should seek prompt medical care even if they have no symptoms.
Early detection of placental abruption is essential because even a relatively stable patient may rapidly progress to a state of hypovolemic shock. Electronic fetal monitoring should be performed for four hours on any pregnant woman who suffers an impact to the torso. In a study by the Jichi Medical School, cardiotocogram and echogram performed immediately after minor maternal trouble can reveal placental abruption and prevent further complications in women who are asymptomatic.