Pediatrics
META ANALYSIS
● Meta-analysis
ZigZag CTG pattern in labor linked to higher risk of operative delivery, low pH, and late decelerations
Journal of perinatal medicine
Published March 30, 2026
Finadri Luca, Mappa Ilenia, Khalil Asma, Rizzo Giuseppe, Lucidi Alessandro, Di Mascio Daniele, Liber…
PubMed ↗
DOI ↗
This systematic review and meta-analysis aimed to determine the intrapartum and perinatal outcomes associated with the ZigZag pattern (ZZP) on cardiotocography (CTG) during labor. The review included six studies encompassing 18,136 fetuses. The analysis compared outcomes between fetuses showing the ZZP—defined as rapid, erratic repetitive oscillations in fetal heart rate with an amplitude >25 bpm—and a control group not showing the pattern. The primary outcomes assessed were operative vaginal delivery, cesarean section, umbilical artery pH <7.1, base excess <-11, mean pH and base excess, admission to the neonatal intensive care unit (NICU), abnormal postnatal brain imaging, and the occurrence of late decelerations later on the CTG trace. The meta-analysis used random-effects models, reporting pooled odds ratios (OR) for categorical variables and pooled mean differences (MD) for continuous variables with 95% confidence intervals (CI). Results showed fetuses with ZZP had significantly higher odds 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 minutes (OR: 2.13, 95% CI 1.05-4.31; p=0.004), and the occurrence of late decelerations later in labor (OR: 9.51, 95% CI 7.80-11.61; p<0.001). The mean umbilical artery pH was significantly lower in the ZZP group (pooled MD: -0.10, 95% CI -0.11 to -0.09; p<0.001). There was no significant difference between groups in the risk of NICU admission (p=0.209), respiratory support after birth (p=0.755), or the value of mean base excess (p=0.156). The abstract did not report data on the outcomes of base excess <-11 or abnormal postnatal brain imaging. The study concludes that the presence of ZZP on CTG during labor is associated with a higher risk of operative delivery and adverse intrapartum and perinatal outcomes.
During labor, doctors monitor a baby's heart rate for signs of distress. A specific pattern—called the ZigZag pattern—has recently caught their attention. It's a rapid, erratic up-and-down swing in the heart rate. A new review of over 18,000 births shows why this pattern is so concerning. Compared to babies without this pattern, those showing the ZigZag pattern were more than twice as likely to need an operative vaginal delivery (using forceps or a vacuum) and nearly twice as likely to be delivered by C-section. They were also more than twice as likely to have a low umbilical cord blood pH (a sign of lower oxygen) and a low Apgar score at five minutes, which checks a newborn's health. Perhaps most strikingly, these babies were over nine times more likely to develop 'late decelerations' later in labor, which are serious heart rate drops after a contraction. The pattern was not linked to a higher risk of needing the NICU or breathing support after birth. The findings confirm that this specific heart rate tracing is a clear red flag during labor, prompting doctors to act quickly to help the baby.
What this means for you: A zigzagging heart rate during labor signals a higher risk of difficult delivery and signs of stress in the newborn.
View Original Abstract ↓
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.