Kleihauer-betke testing is important in all cases of maternal trauma

In maternal trauma, the Kleihauer-Betke (KB) test has traditionally been used to detect transplacental hemorrhage (TPH), so that Rh-negative women could receive appropriate Rh immune prophylaxis. Reasoning that the magnitude of TPH would reflect uterine injury, we evaluated Kleihauer-Betke testing as an independent predictor of preterm labor (PTL) after maternal trauma.

Admissions to the Shock Trauma Center, University of Maryland, from January 1996 to January 2002, were reviewed. Of 30,362 trauma patients admitted, 166 were pregnant, and 93 of these underwent electronic fetal monitoring. Their records were abstracted for demographics, injury type, three separate trauma scores, documented uterine contractions, PTL (contractions with progressive cervical change), and serious perinatal complications. In 71 cases, transplacental hemorrhage was assessed by maternal KB test.

TPH, defined as KB-positive for greater than 0.01 mL of fetal blood in the maternal circulation, occurred in 46 women. Forty-four had documented contractions (25 had overt PTL) and 2 had no contractions. In 25 women with a negative KB test, none had uterine contractions. All patients with contractions or PTL had positive KB tests. By logistic regression, KB test result was the single risk factor associated with PTL (p < 0.001; likelihood ratio, 20.8 for positive KB test). Compared with other sites, abdominal trauma was associated more often with uterine contractions (p < 0.001), PTL (p = 0.001), and a positive KB test (p < 0.001, chi). None of the trauma scoring systems predicted PTL.

Kleihauer-Betke testing accurately predicts the risk of preterm labor after maternal trauma. Clinical assessment does not. With a negative KB test, posttrauma electronic fetal monitoring duration may be limited safely. With a positive KB test, the significant risk of PTL mandates detailed monitoring. KB testing has important advantages to all maternal trauma victims, regardless of Rh status.