New approaches on fetal and maternal intrapartum monitoring

Abstract

Background: Intrapartum fetal monitoring aims to prevent adverse outcomes due to intrapartum asphyxia. Cardiotocography (CTG) is an established method for intrapartum monitoring. The method has high sensitivity, but low specificity and is also user-dependent and linked to both inter- and intraobserver variability. CTG might increase the risk for unnecessary interventions. One suggested method to improve CTG interpretation is computerized monitoring. Other possible ways are improved knowledge about risk factors and proper use of adjunctive technologies. One common adjunctive technology is fetal scalp blood sampling (FBS). Fetal distress is one reason for intrapartum caesarean section, but the main reason is dystocia. Today there is no way to predict dystocia. Studies have suggested that increased levels of lactate in the uterus correlates with dystocia.

Materials and Methods: Study 1 is a prospective observational study of 120 women, investigating methodological aspects of short-term-variation (STV) as a part of computerized fetal monitoring. Paper 2 and 3 study 1070 term pregnancies that underwent FBS. Study 2 is an analysis of lactacidemia in FBS compared to different CTG patterns. Study 3 is an analysis of risk factors for lactacidemia in FBS. Study 4 is a clinical observational study, of 77 women in labor, evaluating if lactate concentration in cervical fluid could be a predictor for dystocia.

Results: STV values differ between internal and external derived values. The two commercial available CTG machines for antenatal STV monitoring perform equal. Late or severe variable decelerations in combination with tachycardia are the CTG patterns with highest frequency of lactacidemia. Isolated reduced variability in an otherwise normal CTG trace is not linked to lactacidemia. Risk factors correlated to lactacidemia are minor language barriers and active bearing down. Increased concentration of lactate in cervical fluid seems to predict operative delivery.

Conclusions: These results suggest several implications on intrapartum monitoring. Intrapartum STV values should preferably be derived from internal monitoring. The same cut-off values could be used for the two commercial available machines for STV monitoring. Late and severe variable decelerations correlate to lactacidemia to the same extent. Isolated reduced variability is not a sign of hypoxia. Use of interpreters can be a possible way to avoid adverse neonatal outcome. Cervical lactate might be a possible tool in predicting dystocia.