Relationship between consistency of meconium-stained amniotic fluid and intrapartum fetal oxygen saturation in the first stage of labor

Abstract

To determine whether pregnancies complicated by meconium-stained amniotic fluid (MSAF) have lower intrapartum fetal oxygen saturation (FSPO2) compared to those with clear amniotic fluid (AF) during the 1st stage of labor. This is a cohort study of women enrolled in a RCT of continuous intrapartum electronic fetal monitoring (EFM) combined with FSPO2 compared to EFM alone. FHR and FSPO2 were recorded from sensor insertion until delivery. Women with singleton pregnancies, gestational age (GA) ≥ 36 0/7 wks and cervical exam 2-6 cm were included. Exclusion criteria were non-vertex presentation, IUFD, and fetal structural/chromosomal defects. Maternal characteristics, FHR abnormalities, intrapartum and delivery outcomes, and FSPO2 were compared between women based on AF consistency (clear AF, thin MSAF, moderate MSAF, and thick MSAF). FSPO2 parameters analyzed were mean FSPO2 and the presence of 2 or more episodes of FSPO2 < 30% lasting at least 2 minutes. Linear and logistic regression analyses were performed to adjust for associated factors and determine the relationship between MSAF consistency and FSPO2. After controlling for maternal age, race, BMI, GA, chorioamnionitis, labor duration and BW < 2500 grams, there was no relationship between the presence of MSAF or MSAF consistency and mean FSPO2 (p > 0.05). However, there was an association between MSAF consistency and the presence of 2 or more episodes of FSPO2 < 30% lasting at least 2 minutes (p = 0.02) [see Table]. Meconium during the first stage of labor was associated with more frequent episodes of FSPO2 < 30%.Tabled 1FSPO2 DataClear AF (N = 1000)Thin MSAF (N = 118)Moderate MSAF (N = 115)Thick MSAF (N = 70)FSPO2 (mean % ± SD)50.4 ± 6.948.8 ± 7.349.6 ± 7.148.5 ± 7.4FSPO2 < 30% for ≥ 2 minutes137 (13.7%)24 (20.9%)27 (23.5%)18 (26.1%) Open table in a new tab