EFFECTS OF BRAXTON-HICKS CONTRACTIONS ON FETAL HEART-RATE VARIATIONS IN NORMAL AND GROWTH-RETARDED FETUSES

The objective of this study was to evaluate whether Braxton-Hicks cont ractions induce changes in fetal heart rate variation in normal and gr owth-retarded fetuses. 110 uncomplicated singleton pregnancies were cr oss-sectionally studied as well as 16 pregnancies complicated by fetal growth retardation secondary to uteroplacental insufficiency. Fetal h eart rate variability was analyzed by a commercially available compute rized system (2CTG Hewlett Packard, Italy) 10 min before and 10 min af ter the Braxton-Hicks contraction. All the included fetal heart rate t racings fulfilled the following criteria: (1) presence of a single Bra xton-Hicks contraction in the 20 min considered; (2) absence of fetal heart rate decelerations after the contraction, and(3) stable fetal he art rate behavioral pattern in the period analyzed. 82 tracings of nor mal fetuses were analyzed during an active fetal heart rate pattern (t ype B) and the remaining 28 during a quiet pattern (type A). In both p atterns no significant differences in delta value, long-term irregular ity, short-term variability and interval index were found before and a fter the contraction. Ah the tracings of growth-retarded fetuses were analyzed during the fetal heart rate pattern A. Short-term variation a nd interval index significantly decreased during the first 5 min after the contraction while no significant differences were found in the ot her indices investigated. The decrease in these indices was significan tly more marked in those fetuses developing fetal distress within 7 da ys. In conclusion, Braxton-Hicks contractions induce a significant dec rease of shortterm variation and interval index only in growth-retarde d fetuses. This can be useful in the early identification of fetal com promise in such fetuses.