Umbilical cord length affects the efficacy of amnioinfusion for repetitive variable deceleration during labor

Objectives: Although amnioinfusion (AI) for repetitive variable deceleration has been reported to reduce the frequency of variable deceleration and cesarean section (CS) rate, CS is sometimes unavoidable even after therapeutic AI. The purpose of this study was to investigate prenatal factors related to the efficacy of therapeutic AI during labor. Methods: This retrospective study investigated 80 singleton pregnancies that underwent transcervical therapeutic AI for repetitive variable deceleration during labor. AI was performed with 500 mL of warmed saline through an intrauterine pressure catheter by gravity infusion. Prenatal factors related to emergency CS for fetal distress even after therapeutic AI were investigated. Results: Emergency CS was performed for 12 of the 80 cases due to fetal distress. Z-score for umbilical cord length was significantly smaller in the CS group (-0.68 SD) than in the vaginal delivery group (0.15 SD, p < .001). No CSs were performed in cases with Z-score for umbilical cord length >-0.05 SD. No significant differences between CS and vaginal delivery groups were seen in gestational age at delivery, cervical dilatation at AI, birth weight, Z-score of birth weight, incidence of the nuchal cord or incidence of abnormal umbilical cord insertion. Conclusions: Therapeutic AI for repetitive variable deceleration was considered useful, in many cases avoiding emergency CS. Short umbilical cord length (lower Z-score) was related to emergency CS after therapeutic AI for repetitive variable deceleration. Umbilical cord length may offer an important factor for assessing the risk of fetal distress that is difficult to avoid, if methods to accurately determine umbilical cord length can be developed.