Fetal heart rate in relation to its variation in normal and growth retarded fetuses

Objectives: (1) to assess the relationship of basal fetal heart rate (FHR) with both long term (LTV) and short term (STV) FHR variation in low-risk pr egnancies, longitudinally from 24 weeks gestation onwards and (2) to invest igate the relationship of FHR with LTV and STV in intrauterine growth retar ded (IUGR) fetuses. Study design: Computerised FHR recordings were made in twenty-nine uncomplicated pregnancies (n = 224) and in twenty-seven IUGR fe tuses who were selected retrospectively from three databases (n = 135). Nom ograms of FHR variation with FHR and GA were constructed using multilevel a nalysis. Results and conclusions: There was a strong negative relationship of FHR with both LTV and STV in the control group (R-2 = 53% and 52%, respe ctively). In the IUGR fetuses, FHR was generally higher than in normal fetu ses whereas LTV and STV were lower. The relationship of FHR with LTV and ST V in the IUGR group was less strong (for both: R-2 = 18%). Correction of FH R variation for basal FHR in the IUGR fetuses only resulted in a slight red uction in the number of recordings with a variation below the normal range. As it does not improve the recognition of fetuses being considered at the highest risk, such a correction of FHR variation for basal FHR is therefore not necessary. Intrafetal consistency, known to be present in healthy fetu ses, was also present in the IUGR fetuses with a low FHR variation. (C) 200 0 Elsevier Science Ireland Ltd. All rights reserved.