When there is particular concern regarding the fetal heart rate tracing the obstetrician may opt for a fetal scalp electrode (FSE). This is screwed into the fetal presenting part through the opening in the cervix (requires ruptured membranes and adequate dilation). This signal is usually more reliable, but entails risks of chorioamnionitis, fetal scalp infection, scalp hematoma, and potential vertical transmission of maternal viruses including HIV and hepatitis.