Intra-partum and perinatal outcomes in fetuses exhibiting ZigZag pattern on cardiotocography trace: a systematic review and meta-analysis

Objectives: Historically, baseline fetal heart rate variability (FHRV) with an amplitude of greater than 25 beats per minute, and lasting for more than 30 min, was defined as the saltatory pattern. Several experimental animal models have reported an association between saltatory pattern and poor perinatal outcomes. However, recent studies have suggested that the classically defined saltatory pattern is very uncommon during labor, and a new CTG pattern, called the “ZigZag” pattern (ZZP), has been reported. ZZP has been defined as a rapid, erratic repetitive oscillations in the FHR with an amplitude of >25 bpm and has been claimed as a potential marker to identify fetuses at risk of intra-partum and perinatal compromise during labour. A recent international expert consensus has recommended that ZZP persisting for >1 min requires an urgent intervention to avoid poor perinatal outcomes. The aim of the present systematic review was to determine the intra-partum and perinatal outcomes of fetuses with the ZZP compared to the control group not showing the ZZP during labor. Methods: Medline, Embase and Cochrane databases were searched. Inclusion criteria were studies reporting the intra-partum and perinatal outcome of fetuses showing compared to those not showing ZZP during labour. The outcomes observed were operative vaginal delivery, caesarean section, umbilical artery pH<7.1, base excess <−11, mean pH and base excess, admission to neonatal intensive care unit (NICU), abnormal post-natal brain imaging and occurrence of late decelerations later on the CTG trace. Random-effect meta-analyses were used to combine data and results reported as pooled odd ratios (OR) for categorical and pooled mean differences (MD) for continuous variables with their 95 % confidence intervals (CI). Results: Six studies (18,136 fetuses) were included. Fetuses showing ZZP on CTG trace during labor had a higher risk of operative vaginal delivery (OR: 2.22, 95 % CI 1.69–2.91; p<0.001), cesarean delivery (OR: 1.71, 95 % CI 1.37–2.15; p<0.001), umbilical artery pH<7.1 (OR: 2.48, 95 % CI 1.56–3.94; p<0.001), Apgar score <7 at 5 min (OR: 2.13, 955 CI 1.05–4.31; p=0.004) and the occurrence of late decelerations later on during labor (OR: 9.51, 95 % CI 7.80–11.61; p<0.001) compared to those not showing this pattern, while there was no difference in the risk of NICU admission (p=0.209) and respiratory support after birth (p=0.755). Likewise, umbilical artery pH was significantly lower in fetuses showing compared to those not showing ZZP during labour (pooled MD: −0.10, 95 % CI −0.11 to −0.09; p<0.001), while there was no difference in the value of mean base excess between the two groups (p=0.156). Conclusions: Fetuses showing the ZZP on CTG trace during labour are at higher risk of operative vaginal delivery, caesarean section and adverse intrapartum and perinatal outcomes.