Absence of accelerations during labor is of little value in interpreting fetal heart rate patterns.

INTRODUCTION: The aim of this study was to investigate the correlation between increasing time since fetal heart rate (FHR) accelerations, positive (no acceleration) stimulation tests and fetal acidemia. MATERIAL AND METHODS: Observational study of FHR recordings from 1070 laboring women with indication for fetal scalp blood sampling (FBS). FHR traces were scrutinized regarding acceleration at FBS and duration since most recent acceleration. The appraiser was blinded to the FBS result. RESULTS: At the first sampling, 8.8% of fetuses had lactate concentration >4.8 mmol/L. There were no differences between those with recent accelerations (≤60 min), and absent accelerations (>60 min or never) prior to FBS (8.3% vs. 8.9%, p = 0.71). Corresponding analyses for subgroups were: fetuses with isolated absence of accelerations, 3.7% vs. 1.5% (p = 0.41), fetuses without decelerations (i.e. reduced variability and/or tachycardia), 6.1% vs. 5.1% (p = 0.81) and fetuses with serious decelerations (i.e. late or complicated variable), 15.0% vs. 16.1% (p = 0.87). Among fetuses with serious decelerations, increasing duration from most recent acceleration had a weak but statistically significant correlation to increased lactate concentration (rs = 0.12, p = 0.03). The positive likelihood ratio for acidemia with no response at FBS was 1.15. CONCLUSION: In a population with FBS performed upon indication, there was no correlation between duration since last FHR acceleration and increased lactate concentration. The majority of fetuses are not acidemic even when the FHR trace is pathological and stimulation tests are only helpful when accelerations are provoked.

Fetal heart rate monitoring of short term variation (STV): a methodological observational study.

BACKGROUND: Cardiotocography (CTG) has high sensitivity, but less specificity in detection of fetal hypoxia. There is need for adjunctive methods easy to apply during labor. Low fetal heart rate short term variation (STV) is predictive for hypoxia during the antenatal period. The objectives of our study were to methodologically evaluate monitoring of STV during labor and to compare two different monitors (Sonicaid™ and EDAN™) for antenatal use. METHODS: A prospective observational study at the obstetric department, Karolinska University hospital, Stockholm (between September 2011 and April 2015). In 100 women of ≥ 36 weeks gestation, STV values were calculated during active labor. In a subset of 20 women we compared STV values between internal and external signal acquisition. Additionally we compared antenatal monitoring with two different monitors in another 20 women. RESULTS: Median STV in 100 fetuses monitored with scalp electrode during labor (EDAN™) was 7.1 msec (range 1.3-25.9) with no difference between early (3-6 cm) and late (7-10 cm) labor (7.1 vs 6.8 msec; p = 0.80). STV calculated from scalp electrode signals were positively correlated with delta-STV (STV internal -external) (R = 0.70; p < 0.01). No significant differences were found between Sonicaid™ and EDAN™ in antenatal external monitoring of STV (median difference 0.9 msec, Spearman Rank Correlation Sonicaid vs delta-STV; R = 0.35; p = 0.14). CONCLUSIONS: Median intrapartum STV was 7.1 msec. Significant differences were found between internal and external signal acquisition, a finding that suggests further intrapartum studies to be analysed separately depending upon type of signal acquisition. Antenatal external monitoring with Sonicaid™ and EDAN™ indicates that the devices perform equally well in the identification of acidemic fetuses. Further studies are needed to assess the clinical value of intrapartum STV.

Cardiotocography patterns and risk of intrapartum fetal acidemia.

AIM: To identify cardiotocography (CTG) patterns associated with increased risk of intrapartum fetal acidemia. METHODS: A prospective observational cohort study of 1070 women with fetal scalp blood sampling (FBS) during labor was conducted at Karolinska University Hospital, Stockholm, Sweden. Women with a nonreassuring CTG pattern underwent FBS, and lactate concentration was measured at the bedside. Lactate concentrations >4.8 mmol/L were defined as fetal acidemia. A senior obstetrician, blinded to the lactate concentration at FBS, visually interpreted the CTG tracings that had prompted FBS. RESULTS: There were 2134 FBSs performed on 1070 laboring women, constituting 11% of all deliveries at this labor ward. The CTG patterns with the highest frequency of lactacidemia at FBS were late or severe variable decelerations combined with tachycardia (20%-25% at first FBS and 33%-49% at last FBS). With a normal baseline fetal heart rate, normal variability, and absence of serious decelerations, the fetal scalp blood lactate concentration at the first FBS was normal in 97.5% of cases. The group with isolated reduced variability had no increased prevalence of acidemia and median lactate concentration did not differ from the normal group. CONCLUSION: Isolated reduced variability is in most cases not a sign of hypoxia. If development of hypoxia is ruled out with one FBS, this pattern does not require monitoring with repetitive FBSs throughout labor. Late decelerations and severe variable decelerations increase the risk for intrapartum fetal metabolic acidemia to the same extent. The combination of these decelerations and tachycardia was associated with the highest rate of fetal metabolic acidemia.

Risk factors for intrapartum acidemia - a cohort study.

PURPOSE: Birth acidemia is associated with short- and long-term morbidity in the child. Optimal intrapartum surveillance and timely interventions may reduce the incidence of these outcomes. Knowledge about conditions which increase the risks might be beneficial for optimal care. The aim with this study was to identify factors which increased the risk for lactacidemia in fetal scalp blood. MATERIALS AND METHODS: A secondary analysis of a cohort study performed at Karolinska University Hospital Stockholm Sweden between February 2009 and February 2011. The study population included 1070 women in labor where fetal scalp blood sampling (FBS) was performed. RESULTS: In a univariate logistic regression analysis for lactate >4.8 mmol/L at FBS, minor language barriers (OR 2.54; 95%CI 1.26-5.11), active bearing down (OR 2.46; 95%CI 1.12-5.39) and maternal height <155 cm (OR 2.15; 95%CI 1.08-4.26) were found as risk factors. In a multivariate logistic regression analysis, minor language barriers (OR 2.21; 95%CI 1.05-4.67) and active pushing (OR 2.68; 95%CI 1.20-6.00) remained significant. CONCLUSIONS: Language barriers, active pushing and short stature were found to be significant risk factors for intrapartum lactacidemia. In the group with minor language problems better use of interpreters might be beneficial.

Neonatal outcome and delivery mode in labors with repetitive fetal scalp blood sampling.

OBJECTIVE: To investigate if repeat (≥ 3) fetal scalp blood sampling (FBS) is associated with increased risk of caesarean delivery and worse neonatal outcome than occasional (1-2) FBS. STUDY DESIGN: Prospective cohort study of women undergoing intrapartum FBS at Karolinska University Hospital, Sweden. FBS with lactate analysis was performed if the attending doctor found the cardiotocography (CTG) tracing suspicious or abnormal. Lactate concentration was measured bedside. As a routine in all deliveries, acid-base analyses were performed on umbilical artery and vein blood immediately after delivery. Main outcome measures were metabolic acidemia in umbilical artery at delivery, Apgar score <7 at 5 min and caesarean delivery. RESULTS: During the study period there were 2134 FBSs performed on 1070 laboring women with a median of two samplings (range 1-8). There were no differences in Apgar score <7 at 5 min or metabolic acidemia in umbilical artery blood at birth between labors with 1-2 FBS and ≥ 3 FBS. Among women who underwent 1-2 FBS, 23% had a caesarean delivery as compared with 42% of those having ≥ 3 FBS. After adjustment for confounders, repeat FBS remained an independent risk factor for caesarean delivery (adj OR 2.05; 95%C.I 1.5-2.8). CONCLUSION: Fetal monitoring with repetitive FBS (≥ 3) during labors with CTG changes is safe for the baby, but the rate of caesarean delivery is doubled as compared to labors where 1-2 FBS are needed. Still, more than 50% of women with repetitive FBS will be delivered vaginally, and 1/3 of these spontaneously.