Variable Heart Rate Decelerations Research Articles

Correlation of arterial fetal base deficit and lactate changes with severity of variable heart rate decelerations in the near-term ovine fetus

Recent guidelines classify variable decelerations without detail as to degree of depth. We hypothesized that variable deceleration severity is highly correlated with fetal base deficit accumulation. Seven near-term fetal sheep underwent a series of graded umbilical cord occlusions resulting in mild (30 bpm decrease), moderate (60 bpm decrease), or severe (decrease of 90 bpm to baseline <70 bpm) variable decelerations at 2.5 minute intervals. Mild, moderate, and severe variable decelerations increased fetal base deficit (0.21 ± 0.03, 0.27 ± 0.03, and 0.54 ± 0.09 mEq/L per minute) in direct proportion to severity. During recovery, fetal base deficit cleared at 0.12 mEq/L per minute. In this model, ovine fetuses can tolerate repetitive mild and moderate variable decelerations with minimal change in base deficit and lactate. In contrast, repetitive severe variable decelerations may result in significant base deficit increases, dependent on frequency. Modified guideline differentiation of mild/moderate vs severe variable decelerations may aid in the interpretation of fetal heart rate tracings and optimization of clinical management paradigms.

Nuchal Cord Detected by Ultrasound at Term is Associated With Mode of Delivery and Perinatal Outcome

Up to 30% of births reportedly are complicated by loops of umbilical around the neck. The clinical significance of the cord remains uncertain. In many cases, it seems harmless, but an increased risk of variable heart rate decelerations has been described, as have relatively high rates of acidemia, low 1-minute Apgar scores, meconium-stained amniotic flood, emergency cesarean section, the need for neonatal resuscitation, admission to intensive care, and, possibly, perinatal death. This prospective study enrolled 352 normal singleton pregnancies in vertex presentation at 37 to 39 weeks gestation. Real-time 2-dimensional ultrasonography was carried out at approximately 38 weeks gestation. Nuchal was detected in 144 of the 352 pregnancies. Both operative vaginal delivery and cesarean section were more frequent in the nuchal group (Χ 2 test, P <.0001). The difference was significant for nulliparous but not for parous women. Nuchal did not correlate significantly with either the amount of amniotic fluid at 38 weeks gestation or intrapartum cardiotocography. There were, however, significant differences between the nuchal and unaffected groups in average 1-minute Apgar scores (7.9 vs 8.3) and 5-minute Apgar scores (9.2 vs 9.5). Birth weights were significantly higher in the nuchal group. Differences in Apgar scores remained significant after correcting scores for birth weight. Ultrasonography detected nuchal with sensitivity of 85% and specificity of 89%. Nulliparous women are more likely to have operative delivery when a nuchal is present at term. The slightly lower Apgar scores associated with the presence of a nuchal might, in large part, reflect a higher rate of operative delivery in these cases.

The effect of variable heart rate decelerations on intraventricular hemorrhage and other perinatal outcomes in preterm infants.

We investigated the hypothesis that repetitive variable heart rate decelerations in labor are associated with an increased incidence of neonatal complications in premature infants. This was a retrospective case-control study. Singleton fetuses weighing between 750 and 2500 g at 25-35 weeks' gestation were considered for the study. Fetuses delivered by Cesarean section prior to labor were excluded. Heart rate traces were retrieved from an electronic archive and were assessed for the presence of variable decelerations. Cases had at least three variable decelerations in the hour prior to delivery and were matched 1:1 with controls for gestation, sex and birth weight. A review of 6500 deliveries yielded 41 matched pairs. The groups were compared for the following outcomes. Measures of acute morbidity were cord pH at delivery, 5-min Apgar score and resuscitation; measures of chronic morbidity were intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis and death. There was no difference in measures of acute morbidity between the groups. The incidence of chronic morbid outcome measures in the cases was six (15%) vs. one (2.5%) in controls (p = 0.01). This study suggests that variable decelerations in preterm infants are associated with chronic morbidity, particularly intraventricular hemorrhage through a mechanism independent of fetal acidemia. Further study is required to determine whether these infants would benefit from early Cesarean section.

The effect of variable heart rate decelerations on intraventricular hemorrhage and other perinatal outcomes in preterm infants

Objective: We investigated the hypothesis that repetitive variable heart rate decelerations in labor are associated with an increased incidence of neonatal complications in premature infants. Methods: This was a retrospective case-control study. Singleton fetuses weighing between 750 and 2500 g at 25-35 weeks' gestation were considered for the study. Fetuses delivered by Cesarean section prior to labor were excluded. Heart rate traces were retrieved from an electronic archive and were assessed for the presence of variable decelerations. Cases had at least three variable decelerations in the hour prior to delivery and were matched 1 : 1 with controls for gestation, sex and birth weight. Results: A review of 6500 deliveries yielded 41 matched pairs. The groups were compared for the following outcomes. Measures of acute morbidity were cord pH at delivery, 5-min Apgar score and resuscitation; measures of chronic morbidity were intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis and death. There was no difference in measures of acute morbidity between the groups. The incidence of chronic morbid outcome measures in the cases was six (15%) vs. one (2.5%) in controls ( p = 0.01). Conclusions: This study suggests that variable decelerations in preterm infants are associated with chronic morbidity, particularly intraventricular hemorrhage through a mechanism independent of fetal acidemia. Further study is required to determine whether these infants would benefit from early Cesarean section.

Amnioinfusion for umbilical cord compression in labour.

Amnioinfusion aims to prevent or relieve umbilical cord compression during labour by infusing a solution into the uterine cavity. The objective of this review was to assess the effects of amnioinfusion on maternal and perinatal outcome for potential or suspected umbilical cord compression or potential amnionitis. The Cochrane Pregnancy and Childbirth Group trials register and the Cochrane Controlled Trials Register were searched. Randomised trials of amnioinfusion compared with no amnioinfusion in women with babies at risk of umbilical cord compression; and women at risk of intrauterine infection. Eligibility and trial quality were assessed by the reviewer. Twelve studies were included. Transcervical amnioinfusion for potential or suspected umbilical cord compression was associated with the following reductions: fetal heart rate decelerations (relative risk 0.54, 95% confidence interval 0.43 to 0.68); caesarean section for suspected fetal distress (relative risk 0.35, 95% confidence interval 0.24 to 0.52); neonatal hospital stay greater than 3 days (relative risk 0.40, 95% confidence interval 0. 26 to 0.62); maternal hospital stay greater than 3 days (relative risk 0.46, 95% 0.29 to 0.74). Transabdominal amnioinfusion showed similar results. Transcervical amnioinfusion to prevent infection in women with membranes ruptured for more than 6 hours was associated with a reduction in puerperal infection (relative risk 0.50, 95% confidence interval 0.26 to 0.97). Amnioinfusion appears to reduce the occurrence of variable heart rate decelerations and lower the use of caesarean section. However the studies were done in settings where fetal distress was not confirmed by fetal blood sampling. The results may therefore only be relevant where caesarean sections are commonly done for abnormal fetal heart rate alone. The trials reviewed are too small to address the possibility of rare but serious maternal adverse effects of amnioinfusion.

Effect of variable heart rate decelerations on perinatal outcome in low birthweight infants

Effect of variable heart rate decelerations on perinatal outcome in low birthweight infants

Variable heart rate decelerations and transcutaneous Po2 during umbilical cord occlusion in fetal monkeys

In five near-term rhesus monkeys under ketamine anesthesia, fetal heart rate, blood pressure, intrauterine pressure, and transcutaneous oxygen tension (tcPo2) were recorded continuously while the umbilical cord was occluded for 15 or 30 seconds. Fetal heart rate decreased 55 ± 19 bpm, (mean ± SD) and 78 ± 20 bpm, respectively, with 15 and 30 second occlusions, while tcPo2 declined 6.0 ± 1.6 and 11.5 ± 3.3 torr, respectively. Fetal hypertension started promptly with cord occlusion and reached a maximum within 5 to 16 seconds; fetal blood pressure decreased thereafter and, in most instances, fell below the baseline until fetal heart rate began to recover. Fetal heart rate decreased within 1 to 2 seconds of cord occlusion. tcPo2 changes were the same, while heart rate changes were attenuated when the fetus was pretreated with 0.2 mg of atropine. These findings support a rapid and marked initial baroreceptor response, followed by a less marked chemoreceptor response. Thirty seconds following cord occlusion, Pao2 had returned to baseline, white tcPo2 was still 3 to 7 torr below baseline, indicating cutaneous vasoconstriction even though systemic blood pressure was normal. Relative heat output required to maintain the tcPo2 electrode temperature at 44°C did not reflect alterations in skin perfusion during periods of cardiovascular change.