Study population
The medical records of all women that presented to the SZMC emergency room between January 2013 and December 2019 due to trauma during pregnancy were reviewed for the following inclusion criteria: viable pregnancy (gestational age >24.0 weeks) and at least one FCM test was obtained during their ER visit or hospitalization. Maternal trauma was defined as any blunt injury occurring during pregnancy resulting in evaluation in the emergency room or hospital admission. We excluded women with penetrating trauma as these are rare; we also excluded women with trauma in whom FCM test was not obtained, as our aim was to assess the predictive role of FCM, and finally we excluded women in whom a FCM test was obtained for reasons other than trauma.
Charts of all eligible women were reviewed and the following data was extracted: patient demographics, obstetric history, details of maternal injury, presence of preterm contractions, preterm labor (PTL), and placental abruption, surgical procedure(s) (if any), obstetric complications, and neonatal outcomes: fetal injury and death. We also devised an anatomic scoring system based on information in the medical chart, to provide an overall score for patients with multiple injuries: the Injury Severity Score (ISS).
The FCM data was extracted and recorded as both categorical values (FCM-positive or -negative) and continuous data (TPH volume when positive). According to our medical center protocol, FCM is obtained when the following criteria are met: direct abdominal injury, all cases of motor vehicle accident (MVA), and other blunt trauma cases where the attending physician deems it necessary.
Furthermore, according to local policy all such women undergo thorough evaluation including detailed history, past and current pregnancy information, trauma mechanism, acuteness/severity of the case, symptoms/signs of acute abdomen, vital signs, and assessment for uterine contractions and/or premature labor. Also, all women undergo fetal heart rate monitoring to detect fetal compromise, tocodynamometer for monitoring and recording uterine contractions, and sonographic examination of the fetus and placenta by certificated technician and/or obstetrician at the time of admission. Finally, decision regarding any surgical intervention is made by a senior physician.
Obstetric issues were managed by the perinatology team, consistent with the multidisciplinary approach at the SZMC and as recommended by the ATLS and ACOG 19,20. Accordingly, women with any signs of regular uterine contractions (more than one in 10 minutes), vaginal bleeding, rupture of amniotic membranes, serious maternal injury, significant abdominal/uterine pain or fetal tachycardia, decelerations, or non-reassuring fetal heart rate tracing, were monitored for a period of no less than 24 hours. When uterine contractions were associated with progressive cervical dilation, the definition of PTL was met and clinical management protocols implemented.
Following assessment by the obstetric team and judged necessary, five milliliters of maternal venous blood were collected into EDTA tubes, sent to the laboratory for FCM, stored at 4°C and processed within 72 hours of collection. The results of the FCM were typically available either at noon of the same day or the following day, and usually were not used for acute management decisions. Rather, FCM was used to decide whether to prolong observation time beyond 24 hours. Rarely, more than one blood sample was obtained. In women with a positive FCM test, another blood sample was obtained. The quantification of fetal blood hemorrhage by FCM has been described in detail elsewhere13,21. FCM was considered positive above 30 ml FMH, a volume that may trigger Rh sensitization 15.