Diurnal variations of short-term variation and the impact of multiple recordings on measurement accuracy.
Short-term variation (STV) from computerized cardiotocogram heart rate analysis is a parameter that complements decision making, regarding the delivery of fetuses in several high-risk situations. Although studies on the effects of gestational age and fetal pathology are convincing, there is a lack of data exploring diurnal variation and the adequacy of a single measurement.



In this prospective observational study, fetal STV was monitored with the AN24 fetal ECG monitor (Monica Healthcare) each hour for at least 10 h in total, beginning at different times. This resulted in data covering all 24 h of the day. Seventy fetuses, low risk with respect to conditions accessible to heart rate monitoring (median 37th week of gestation) were monitored for an average of 12 h. Results of STV per hour were categorized as 'compromised' (STV<4 ms) or 'healthy', (STV⩾4 ms) to calculate the model of predictability.



The model proposed (STV of 'healthy' fetuses: 9.6±2.6 ms, 'compromised' fetuses 3.0±0.5 ms, prevalence 1%) leads to a positive predictive value of 39%, which increased to 68 or 80% given two or three pathological (STV<4 ms) measurements, respectively. Diurnal variation was not observed.



Single pathological STV values should be corroborated by further measurements in a 24-h interval in otherwise low-risk fetuses before inducing delivery. This may help to avoid unnecessary early births and give the fetus valuable days for intrauterine maturity.
Martin Luther University, Maternity Clinic/Perinatal Treatment Center, Halle (Saale), Germany.
G
G
Seliger
Clinical Trial Centre, University of Leipzig, Leipzig, Germany.
D
D
Petroff
St Elisabeth Hospital's Clinic for Women's Health and Perinatal Care, Halle (Saale), Germany.
S
S
Seeger
Hans Berger Department of Neurology, Biomagnetic Center, Jena University Hospital, Jena, Germany.
D
D
Hoyer
Martin Luther University, Maternity Clinic/Perinatal Treatment Center, Halle (Saale), Germany.
M
M
Tchirikov
Department of Obstetrics, Jena University Hospital, Jena, Germany.
U
U
Schneider
D000293:Adolescent; D000328:Adult; D015148:Cardiotocography / Q000379:methods*; D002940:Circadian Rhythm; D005260:Female; D005323:Fetal Monitoring / Q000379:methods*; D005858:Germany; D005865:Gestational Age; D006340:Heart Rate, Fetal; D006801:Humans; D016014:Linear Models; D011247:Pregnancy; D011446:Prospective Studies; D055815:Young Adult