Editing Cardiotocography (section)

===Baseline FHR variability===
Moderate baseline fetal heart rate variability reflects the delivery of oxygen to the fetal [[central nervous system]]. Its presence is reassuring in predicting an absence of [[metabolic acidemia]] and [[Intrauterine hypoxia|hypoxic]] injury to the fetus at the time it is observed.<ref name=nic/> In contrast, the presence of minimal baseline FHR variability, or an absence of FHR variability, does not reliably predict fetal acidemia or hypoxia; lack of moderate baseline FHR variability may be a result of the fetal sleep cycle, medications, extreme prematurity, congenital anomalies, or pre-existing neurological injury.<ref name=nic/> Furthermore, increased (or marked) baseline FHR variability (see "Zigzag pattern" and "Saltatory pattern" sections below) is associated with adverse fetal and neonatal outcomes.<ref name=zigzag>{{Cite journal|last1=Tarvonen|first1=Mikko|last2=Hovi|first2=Petteri|last3=Sainio|first3=Susanna|last4=Vuorela|first4=Piia|last5=Andersson|first5=Sture|last6=Teramo|first6=Kari|date=2020-09-27|title=Intrapartum zigzag pattern of fetal heart rate is an early sign of fetal hypoxia: A large obstetric retrospective cohort study|journal=[[Acta Obstetricia et Gynecologica Scandinavica]]|volume=100|issue=2|pages=252–262|language=en|doi=10.1111/aogs.14007|pmid=32981037|pmc=7894352|issn=0001-6349|doi-access=free}}</ref><ref name=Tarvonen2019/><ref name=saltatory/><ref>{{Cite journal|last1=Polnaszek|first1=Brock|last2=López|first2=Julia D.|last3=Clark|first3=Reece|last4=Raghuraman|first4=Nandini|last5=Macones|first5=George A.|last6=Cahill|first6=Alison G.|date=2019-10-02|title=Marked variability in intrapartum electronic fetal heart rate patterns: association with neonatal morbidity and abnormal arterial cord gas|journal=[[Journal of Perinatology]]|volume=40|issue=1|pages=56–62|doi=10.1038/s41372-019-0520-9|pmid=31578422|pmc=7202403|issn=0743-8346}}</ref> Based on the duration of the change, increased (i.e. marked) baseline variability is divided into two terms: zigzag pattern and saltatory pattern of FHR.<ref name=zigzag/><ref>{{Cite journal|last=Tarvonen|first=Mikko|title=Factors Associated with Intrapartum ZigZag Pattern of Fetal Heart Rate: A Retrospective One-Year Cohort Study of 5150 Singleton Childbirths|url=https://www.ejog.org/article/S0301-2115(20)30850-2/pdf|journal=European Journal of Obstetrics, Gynecology, and Reproductive Biology|year=2021|volume=258|pages=118–125|doi=10.1016/j.ejogrb.2020.12.056|pmid=33421808|s2cid=231437287 |via=|url-access=subscription}}</ref> The NICHD nomenclature defines baseline FHR variability as:<ref name=nic/>
{{blockquote|text=Baseline FHR variability is determined in a 10-minute window, excluding accelerations and decelerations. Baseline FHR variability is defined as fluctuations in the baseline FHR that are irregular in amplitude and frequency. The fluctuations are visually quantitated as the amplitude of the peak-to-trough in beats per minute. Furthermore, the baseline FHR variability is categorized by the quantitated amplitude as:
*Absent – undetectable
*Minimal – greater than undetectable, but 5 or fewer beats per minute
*Moderate – 6–25 beats per minute
*Marked – 25 or more beats per minute}}<ref name="John Wiley & Sons">{{Cite book |last1=Norwitz |first1=Errol R. |url=https://books.google.com/books?id=As2CDwAAQBAJ&pg=PT1013 |title=Evidence-based Obstetrics and Gynecology |last2=Zelop |first2=Carolyn M. |last3=Miller |first3=David A. |last4=Keefe |first4=David L. |date=2018-12-20 |publisher=John Wiley & Sons |isbn=978-1-119-07295-9 |language=en}}</ref>{{verify source|date=November 2020}}