Reduced fetal movement during pregnancy: Is the Kleihauer-Betke test really useful?

Reduced fetal movement (rFM) is a frequent cause of consultation during the pregnancy and can reveal feto-maternal hemorrhage (FMH) that is sometimes responsible of severe fetal anemia. Our primary objective was to evaluate the contribution of the KBT in case of rFM. Our secondary objective was to compare it with ultrasound examination including peak systolic velocity of the middle cerebral artery (MCA-PSV) to predict neonatal anemia.

We conducted a retrospective study from January 2016 to December 2017 at Armand-Trousseau Hospital in Paris. We analyzed all patients consulting for rFM from 18 to 41 weeks of gestation. We compared the performance of KBT and MCA-PSV to predict neonatal anemia (Hemoglobin at birth under 13.5 g/dL) and severe neonatal anemia (Hb < 10 g/dL).

Among the 338 patients, 327 KBT (96.7%) were performed. KBT was found positive in three cases (0.9%). Only one neonate (0.3%) presented with severe anemia requiring a postnatal transfusion. MCA-PSV was performed in 166 cases (49.1%). KBT and MCA-PSV were significantly correlated with neonatal hemoglobin at birth. KBT was better than MCA-PSV to predict neonatal anemia, while MCA-PSV was better than KBT to predict moderate to severe anemia. The KBT and MCA-PSV Doppler had excellent sensitivity and predictive negative values (100%), but they had poor predictive positive values for severe neonatal anemia.

In case of decreased fetal movement, we suggest performing fetal cerebral Doppler. MCA-PSV could suffice in first approach. KBT may be performed if there is suspicion of fetal anemia in order to confirm FMH.