Cardiotocographic data
Analysis of the CTG tracing must be systematic, regular and recorded on the partogram. Depending on whether or not risk factors are present, analysis every 15 to 30 minutes is recommended, whether or not a central monitoring unit is used (Fournié and Boog 2004[5], CNGOF 2007[4]). Given the pathophysiological data discussed previously, the preceding part of the tracing must be reviewed before analysing a segment.
Four criteria are used for the visual analysis of the FHR (Fig. 1.6):
- the baseline,
- variability,
- accelerations,
- and decelerations, the latter being interpreted in relation to the contractions,
- provided that the signals are properly captured and the contractions are visible;
- we can add to this the monitoring of the maternal heart rate (MHR) as recommended by Ayres de Campos 2015b[2] and Kiely 2019[6].
The longitudinal study by Amorim-Costa 2016[1], involving a total of 145 patients and 1,049 tracings collected between 24 and 41 weeks and analysed automatically by the Omniview-SisPorto® 3.6 system, showed that the baseline (LDB) and variability evolved in opposite directions during pregnancy due to the progressive predominance of the parasympathetic system (Fig. 1.7 and 1.8). Long-term variability (LTV) is the mean difference between the maximum and minimum FHR values within a sliding 1-minute window, accelerations and decelerations not being taken into account. Short-term variation (STV) over one minute is the mean of the 16 means of the differences between successive beats within 16 intervals of 3.75 s (see Section “Short-term variation”).
Learning to analyse the FHR reduces analysis errors. It is recommended to promote and develop theoretical and practical training (CNGOF 2007[4], Ugwumadu 2016[8], Nzelu 2018[7]).
For our part, we have developed an online learning website called eRCF (http://ercf.univ-catholille.fr/), which we invite you to visit…
Now let's get to the heart of the matter…
References
- Amorim-Costa C., Costa-Santos C., Ayres-de Campos D., et Bernardes J. Longitudinal evaluation of computerized cardiotocographic parameters throughout pregnancy in normal fetuses: A prospective cohort study. Acta Obstet Gynecol Scand, 95 (10): 1143–1152, Oct. 2016. ISSN 0001-6349, 1600-0412. doi: 10.1111/aogs.12932. ↩
- Ayres-de-Campos D., Spong C. Y., et Chandraharan E. FIGO consensus guidelines on intrapartum fetal monitoring: Cardiotocography. International Journal of Gynecology & Obstetrics, 131 (1): 13–24, 2015b. ISSN 0020-7292. doi: 10.1016/j.ijgo.2015.06.020. ↩
- Boudet S., Houzé de l'Aulnoit A., Demailly R., Peyrodie L., Beuscart R., et Houzé de l'Aulnoit D. Fetal heart rate baseline computation with a weighted median filter. Computers in Biology and Medicine, 114: 103468, 2019. ISSN 0010-4825. doi: j.compbiomed.2019.103468. doi.org/j.compbiomed.2019.103468
- CNGOF. Recommandations pour la pratique clinique : Modalités de surveillance fœtale pendant le travail, 2007. ↩
- Fournié A. et Boog G. Étude du rythme cardiaque fœtal. EMC - Gynécologie-Obstétrique, 1 (1): 22–50, Feb. 2004. ISSN 17626145. doi: 10.1016/j.emcgo.2003.11.002. ↩
- Kiely D. J., Oppenheimer L. W., et Dornan J. C. Unrecognized maternal heart rate artefact in cases of perinatal mortality reported to the United States Food and Drug Administration from 2009 to 2019: A critical patient safety issue. BMC Pregnancy and Childbirth, 19 (1): 1–10, 2019. ISSN 1471-2393. ↩
- Nzelu O. Human Factors: The Dirty Dozen in CTG misinterpretation. GJORM, 6 (2), Oct. 2018. ISSN 25758594. doi: 10.19080/GJORM.2018.06.555683. ↩
- Ugwumadu A., Steer P., Parer B., Carbone B., Vayssiere C., Maso G., et Arulkumaran S. Time to optimise and enforce training in interpretation of intrapartum cardiotocograph. BJOG: An International Journal of Obstetrics & Gynaecology, 123 (6): 866–869, 2016. ISSN 1470-0328. ↩