12/5/2023 0 Comments Normal fetal heart rate at 6 weeks![]() ![]() We have published the plan to do the analysis and have publicly asked for feedback. This assessment of the situation and the existing “evidence base” is based on the following elements. Up to now, ranges such as 110 to 150 bpm or 110 to 160 bpm ( American Congress of Obstetricians and Gynecologists, 2009 Deutsche Gesellschaft für Gynäkologie und Geburtshilfe, 2010 Macones et al., 2008 Manassiev et al., 1998 National Institute for Health and Clinical Excellence (NICE), 2007 Perinatal Committee of the Japan Society of Obstetrics and Gynecology, 2009 Royal Australian and New Zealand College of Obstetricians and Gynaecologists, 2006 Society of Obstetrics and Gynaecologists of Canada, 2007) are also used, widely based on expert opinion rather than evidence. This consensus replaced the former range of 120 to 160 bpm, as there was evidence pointing to worse fetal outcome for baselines higher than 160 bpm ( Saling, 1966). ![]() The FIGO guidelines, despite some well-known shortcomings, “remain the sole broad international consensus document in FHR monitoring” ( Diogo & Joao, 2010). The current international guidelines of the Fédération Internationale de Gynécologie et d’Obstétrique (FIGO) ( Rooth, Huch & Huch, 1987), based on consensus during the 1985 conference, recommend a normal range of the FHR from 110 to 150 beats per minute (bpm). However, currently, there is not even agreement on the normal range of the baseline of the FHR, although, as Massaniev stated in 1996, “baseline rate provides valuable information on which we plan our further actions” ( Manassiew, 1996). Therefore it seems natural to assume that further work on improving definitions and standardization by using computerized methods will further improve the monitoring systems. In a recent Cochrane review no difference in outcome could be found when looking at potential improvements through the use of CTG monitoring, but, remarkably, the conclusion was different when computerized interpretation of CTG traces was taken into account: “when computerized interpretation of the CTG trace was used, the findings looked promising” ( Grivell et al., 2012). Standardizing management of variant intrapartum FHR tracings was suggested to reduce this variability and to lead to improvement in fetal outcome ( Downs & Zlomke, 2007). One potential reason is the wide variability in clinical decision making associated with its use. A detailed meta-analysis of available studies on the use of intrapartum cardiotocogram showed reduction of perinatal mortality by 50%, but an increase of operative intervention by factor 2.5 ( Vintzileos et al., 1995). However, in several randomized trials it became evident that there is only limited efficacy in improving fetal outcome using CTG antenatally ( Pattison & McCowan, 2004). Recording of fetal heart rate (FHR) via cardiotocography (CTG) monitoring is routinely performed as an important part of antepartum and intrapartum care. However, further studies should confirm that such asymmetric alarm limits are safe, with a particular focus on the lower bound, and should give insights about how to show and further improve the usefulness of the widely used practice of CTG monitoring. Many international guidelines define ranges of 110 to 160 bpm which seem to be safe in daily practice. Normal ranges for FHR are 120 to 160 bpm. FHR decreases slightly during gestation.Ĭonclusions. Validation in all three data sets identified 120 to 160 bpm as the correct symmetric “normal range”. Based on the training data set, the “best” FHR range was 115 or 120 to 160 bpm. After analyzing 40% of the dataset as “training set” from one hospital generating a hypothetical normal baseline range, evaluation of external validity on the other 60% of the data was performed using data from later years in the same hospital and externally using data from the two other hospitals. For each tracing, the baseline FHR was extracted by eliminating accelerations/decelerations and averaging based on the “delayed moving windows” algorithm. We analyzed all recorded cardiotocography tracings of singleton pregnancies in three German medical centers from 2000 to 2007 and identified 78,852 tracings of sufficient quality. We started with a precise definition of “normality” and performed a retrospective computerized analysis of electronically recorded FHR tracings. ![]() Current international guidelines recommend for the normal fetal heart rate (FHR) baseline different ranges of 110 to 150 beats per minute (bpm) or 110 to 160 bpm. There is no consensus about the normal fetal heart rate.
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