Introduction
Trauma during pregnancy occurs in 1 to 12% of pregnancies1. In an attempt to optimize maternal and neonatal outcomes, predictors of serious perinatal consequences such as placental abruption, preterm delivery, lethal fetal injury, and uterine rupture, in addition to the full range of maternal injuries, have been sought2–6. The most significant risk factor for adverse maternal and neonatal outcomes is severe injury. Fortunately however, severe trauma occurs in only a minority of pregnant trauma patients7.
As most trauma cases during pregnancy are mild, continuing exploration of risk factors for adverse maternal and neonatal outcomes in this setting is clinically important8. We hypothesized that feto-maternal hemorrhage (FMH), also called transplacental hemorrhage (TPH), could possibly be associated with the risk of adverse maternal and neonatal outcome.
FMH may be diagnosed via flow cytometry (FCM) for detection and quantification of fetal red blood cells, or by Kleihauer–Betke test (KB test). FCM is an accurate method to evaluate this type of bleeding9–14 , based on the identification of fetal erythrocytes containing hemoglobin F (HbF) with an anti-HbF monoclonal antibody. The FCM method can analyze a very high number of erythrocytes, improving the sensitivity and specificity of the KB test15,16. Massive TPH associated with complete placental abruption is rare and clinically evident, making FCM testing superfluous. FCM testing is commonly used to detect TPH in pregnant trauma women. Some studies have suggested that a positive KB test in the setting of trauma during pregnancy may be predictive of adverse perinatal outcomes, however other studies have shown differently17,18. We failed to find similar studies assessing the utility of FCM in this setting.
In this study, we aimed to assess whether positive FCM is associated with adverse perinatal outcomes in pregnant patients experiencing mild trauma.