Misidentification of maternal for fetal heart rate patterns after delivery of the first twin

Background: The 2nd born in twin delivery is at higher risk of fetal asphyxia. We tested the hypothesis that inadequate, fetal heart rate (FHR) monitoring has contributed to an inadvertent outcome. Study design: A database was reviewed consisting of 41 twin deliveries with a pH in the umbilical artery of the 2nd twin below 7.05. Cardiotocograms were examined for possible signs of a maternal instead of a fetal origin of the heart rate pattern. Results: In four of the reviewed cases, a good outcome had been anticipated by the attending physician based on the cardiotocogram, whereas the 2nd twin was born with low Apgar scores and a low pH of the umbilical artery. In retrospect it was concluded that the recorded heart rate pattern was of maternal origin. In all four cases the heart rate tracings had characteristics typical for a maternal origin. Conclusion: Misidentifying the maternal for the fetal heart rate increases the risk that a compromised fetal condition is missed. This occurrence may contribute to the increased incidence of fetal asphyxia in 2nd twins.