Le rythme cardiaque fœtal de base après 40 SA en début de travail est prédictif de la morbidité néonatale

Abstract

Introduction: Fetal heart rate (FHR) is a key indicator of fetal vitality, analysed at the onset of obstetric labour. Current classifications do not take gestational age into account, although some studies suggest that the basic rhythm (RDB) decreases physiologically with advancing pregnancy. The aim of this study was to assess whether an ABR greater than 140 bpm after 40 weeks’ amenorrhoea (SA) is associated with increased neonatal morbidity.
Methodology: This was a single-centre retrospective cohort study. The records of 936 patients admitted in spontaneous labour between 40 SA and 40 SA+6 days were analysed (from the first 20 minutes of monitoring on arrival in the delivery room). Two groups were formed:
• Group 1: RDB ≤ 140 bpm (n=826)
• Group 2: RDB > 140 bpm (n=110)
Neonatal morbidity was assessed using a composite score including: arterial pH < 7.10, APGAR score < 7 at 5 minutes, need for resuscitation and transfer to neonatal intensive care. Maternal outcomes were also studied (route of delivery and post-partum haemorrhage).
Results: Neonatal morbidity was significantly higher in the group with an IFEN > 140 bpm (30.9% versus 14.8%; p<0.0001). Multivariate analysis confirmed this association, with an adjusted odds ratio of 2.51 [1.58; 4.01] (p=0.0001). in addition, the caesarean section rate was higher in the group with an RDB > 140 bpm (9.1% vs 4.2%; p=0.025). a higher proportion of meconium amniotic fluid was found in this group (40% vs 18.4%; p < 0.0001).
Discussion: These results suggest that an IFR > 140 bpm after 40 days’ gestation is a predictive factor for neonatal and maternal complications. These observations confirm previous studies showing that normal fetal heart rate decreases with gestational age. They highlight the need to adapt the thresholds for normal FHR according to gestational age in order to improve patient management.
Conclusion: An RDB > 140 bpm in term fœtuses is associated with an increased risk of neonatal morbidity. These results argue in favour of increased surveillance of these fœtuses and the possible use of additional monitoring methods during labour.