Braxton-Hicks contractions and fetal breathing movements

Approaches to Preventing Intrapartum Fetal Injury

Electronic fetal monitoring (EFM) was introduced into obstetric practice in 1970 as a test to identify early deterioration of fetal acid-base balance in the expectation that prompt intervention ("rescue") would reduce neonatal morbidity and mortality. Clinical trials using a variety of visual or computer-based classifications and algorithms for intervention have failed repeatedly to demonstrate improved immediate or long-term outcomes with this technique, which has, however, contributed to an increased rate of operative deliveries (deemed "unnecessary"). In this review, we discuss the limitations of current classifications of FHR patterns and management guidelines based on them. We argue that these clinical and computer-based formulations pay too much attention to the detection of systemic fetal acidosis/hypoxia and too little attention not only to the pathophysiology of FHR patterns but to the provenance of fetal neurological injury and to the relationship of intrapartum injury to the condition of the newborn. Although they do not reliably predict fetal acidosis, FHR patterns, properly interpreted in the context of the clinical circumstances, do reliably identify fetal neurological integrity (behavior) and are a biomarker of fetal neurological injury (separate from asphyxia). They provide insight into the mechanisms and trajectory (evolution) of any hypoxic or ischemic threat to the fetus and have particular promise in signaling preventive measures (1) to enhance the outcome, (2) to reduce the frequency of "abnormal" FHR patterns that require urgent intervention, and (3) to inform the decision to provide neuroprotection to the newborn.

Late-onset fetal cardiac decelerations associated with fetal breathing movements

BACKGROUND

While late decelerations are regarded as signs of fetal hypoxemia, fetal breathing movements (FBM) associated with late decelerations invariably have normal outcomes. Could late decelerations sometimes represent FBM?

MATERIALS AND METHODS

Six patients between 37 and 42 weeks' gestation with 'late decelerations' associated with FBM (by ultrasound or tocodynamometer) during ante- or intrapartum monitoring were evaluated. Three were at high risk (diabetes, postdates, intrauterine growth restriction) and three were at low-risk.

RESULTS

'Late decelerations' arose in previously reassuring tracings. Oxygen or positional change had no effect. The decelerations were variable in length and shallow, and contained increased variability. Normal baseline rate and variability were maintained after the deceleration. Neonatal outcomes were normal.

CONCLUSION

'Late decelerations' as described are associated with normal outcome and may represent FBM. This understanding may reduce unnecessary interventions.

Fetal breathing movements in late diabetic pregnancy: relationship to fetal heart rate patterns and Braxton Hicks' contractions

In type-1 diabetic pregnancy, the occurrence of fetal breathing movements (FBM) was studied in relation to the fetal heart rate patterns (HRPs) A and B and to Braxton Hicks' contractions. Simultaneous 2-h recordings of fetal heart rate and body, eye and breathing movements were available for analysis (n = 44). These recordings were made in 20 fetuses of diabetic women at 32-38 weeks of gestation. Uterine activity was monitored at 36 and 38 weeks. For all recordings combined, the median incidences of FBM during HRPs A and B were 23% and 41%, respectively (NS). At low overall breathing activity (< 50% of total observation time), FBM were more numerous during HRP B than during HRP A in 83% of the recordings. However, if the overall breathing activity exceeded 50% of time FBM were preferentially made during HRP A in 93% of the recordings. This relationship was most pronounced at 38 weeks. These results corroborate our previous findings in the healthy near-term fetus. They show even more clearly that the state-dependent occurrence of FBM depends on the fetus' drive to breathe. During the recordings, breathing activity remained unchanged at all gestational ages studied, in contrast to the gradual decline in FBM seen in normal pregnancy. Braxton Hicks's contractions had no effect on FBM, which differs from the specific distribution of FBM during uterine contractions as previously found in uncomplicated pregnancies. We conclude that FBM in late diabetic pregnancy are not influenced by Braxton Hicks' contractions and that they do not show a clear-cut state-dependency. The (neural) mechanism underlying FBM differs from that in normal pregnancy.

Braxton Hicks' contractions and motor behavior in the near-term human fetus

The transient relationship between Braxton Hicks' contractions and fetal motor behavior was studied in 14 healthy nulliparous women near term. Two-hour recordings of fetal heart rate and uterine contractions and of real-time scanning for fetal body movements, breathing, and eye movements were made. The recordings were divided into state 1F and non-state 1F. Braxton Hicks' contractions were not influenced by fetal behavioral states and state changes were not related to these contractions. Fetal body movements did not stimulate contractions, but contractions coincided with a specific clustering of body movements during the ascending part of contractions. Breathing was clustered during the descending part of short-lasting contractions but decreased gradually during the long-lasting ones. Heart rate variation was increased during contractions.

Effects of hypoxemic events on breathing, body movements, and heart rate variation: a study in growth-retarded human fetuses

In 14 growth-retarded human fetuses, breathing and body movements were studied before, during, and after late heart rate decelerations. Heart rate variation was measured before and after the decelerations. Breathing and body movements were significantly reduced during and after the deceleration. Heart rate variation was reduced after the decelerative episode. Since late heart rate decelerations are presumably signs of acute fetal hypoxemia, there is evidence that these reductions are caused by hypoxemia. The results suggest, furthermore, that just as in fetal sheep, these changes might be mediated by a change in brain activity state.