Results
During the study period, FCM test was obtained in 1296 pregnant women (Figure 1). Of these, 273 tests were performed for non- trauma indications and were excluded. Of the 1023 remaining, 387 (38%) were collected due to MVA, 367 (36%) due to fall, 353 (35%) had direct abdominal injury, and 14 (1%) had other mechanisms of trauma. (Some women had more than one mechanism of trauma recorded).
In 914 (89.3%) women who were evaluated due to a trauma incident during pregnancy some FMH was detected. In 119 (11.6%) women FCM test was considered positive (≥0.03/≥30 ml) with median result of 0.03 [0.03-0.04] and in 904 (88.4%) women FCM test was negative ((≤0.03/≤30 ml) with median result of 0.01 [0.01-0.02].
Table 1 presents the demographic and obstetric characteristics of the study groups. The gestational age at trauma did not differ between the groups. Also, no differences were noted in the gravidity/parity order or the number of previous miscarriages/cesarean deliveries. Accordingly, the rates of fertility treatments, multifetal gestation, and hypertensive or diabetic disorders of pregnancy were comparable between the groups.
The clinicopathological characteristics of the trauma event and short term maternal and neonatal outcomes, stratified by FCM negative or positive results, are presented in Table 2. Trauma mechanism did not differ between the groups. In addition, no differences were noted in the ISS and the maternal symptoms, including vaginal bleeding, uterine contractions, decreased fetal movements, rupture of the membranes, clinical or sonographic signs of placental abruption, or fetal death. However, the rate of trauma injury necessitating assessment by non-obstetric specialty was statistically higher in the positive FCM group (49.6% vs 40.5%, p=0.06). Nevertheless, the type of hospitalization, rate of non-obstetrical surgery, and the rate of delivery during hospitalization were also similar between the groups. However, length of stay (days) was statistically longer in the positive FCM group (1.4±1.8 vs 1.1±1.6, p=0.03).
Delivery information was available for 650/1023 (63.5%) women. The demographic and obstetric characteristics and the positive FCM rates of women who deliver in our medical center were mostly similar to those who did not deliver in our center. However, women who delivered in our medical center had higher rates of vaginal bleeding and uterine contractions at admission (supplementary table 1) .
Maternal and neonatal delivery outcomes stratified by FCM results is shown in Table 3. Of the women with available delivery information, 84 women (70.6%) had positive FCM results and 566 (62.6%) had negative FCM (p=0.09). No cases of fetal death were noted during trauma admission in both groups. The other maternal and neonatal delivery outcomes, including the composite adverse outcomes, were similar in both groups.
In order to evaluate the independent association between positive FCM and composite adverse outcome we fitted a multivariate model. We included all variables found to be significantly associated with composite adverse outcome in the univariate analysis (not presented): vaginal bleeding at admission, uterine contractions at admission, multifetal gestation, and hospitalization. The multivariate model revealed (in order of risk magnitude) that vaginal bleeding at admission, multifetal gestation and hospitalization were independently associated with the composite adverse outcome. However, the association between positive FCM and composite adverse maternal and neonatal outcome was not significant (adjusted OR 0.42, 95% CI 0.16-1.11, p=0.08), Table 4 .
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