Key result
Fetal heart rate characteristics changed with increasing gestational age, with baseline rate decreasing from 137.5 bpm at 28-29 weeks to 132.8 bpm at 38-39 weeks.
Why the study?
The study aimed to comprehensively clarify the characteristics of fetal heart rate with increasing gestational age in low-risk pregnant women during the third trimester using computerized analysis of long-range monitoring.
Observational (n=85)
Fetal heart rate characteristics change gradually during the third trimester, with the most obvious changes in variability occurring at 32-33 weeks of gestation.
Answers are grounded in this paper and cite their sources.
Gestational age-specific FHR norms may refine third-trimester monitoring interpretation; this Level 4 analysis leaves open prospective validation before practice change.
BACKGROUND: With computerized analysis of fetal heart rate(FHR) data from long-range monitoring, we aimed to comprehensively clarify the characteristics of FHR with increasing gestational age in low-risk pregnant women during the third trimester of pregnancy. METHODS: This was an observational study. 85 fetuses of low-risk pregnant women were included. The data covered 28 ∼ 40 weeks of gestation, and 125 cases of FHR monitoring from 85 fetuses were totally collected. The FHR baseline rate, variability, and acceleration were computationally calculated, analyzed and compared. RESULTS: The average effective monitoring time for each case was 13.9 ± 4.3 h. FHR baseline gradually decreased as the gestational age progressed, and the maximum FHR baseline appeared at 28-29 weeks, which was 137.5 (133.0, 141.3) bpm, whereas the minimum FHR baseline appeared at 38-39 weeks, that was 132.8 (128.1, 138.4) bpm. FHR variability fluctuated in (4-12）bpm. It gradually increased from 28 to 33 weeks of gestation, reached the maximum of 7.6 (6.0-9.4) bpm, and then decreased until full-term pregnancy. The moderate variability proportion of FHR gradually increased from 28 weeks of gestation, peaked at 32-33 weeks as 65.8%, and then gradually decreased to 56.2% at 37 weeks, which was maintained at this level until 39 weeks. The variation tendency of minimal variability proportion was opposite to moderate variability proportion. When it reached 40 weeks, the minimal and moderate variability proportions were 50.0% and 49.0%, respectively. The FHR acceleration area showed no trend change during the third trimester, while fluctuated in (29.5-42.4) lattices/h. CONCLUSION: This study revealed that the characteristics of FHR gradually changed with increasing gestational age, and the most obvious change was observed at 32-33 weeks, demonstrating that the specific gestational weeks may be an important period for the physiological bias of FHR tends to mature.
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Li et al. (2021) conducted an observational in Low-risk pregnancy (n=85). Increasing gestational age was evaluated on Fetal heart rate (FHR) baseline rate, variability, and acceleration. Fetal heart rate characteristics changed with increasing gestational age, with baseline rate decreasing from 137.5 bpm at 28-29 weeks to 132.8 bpm at 38-39 weeks.
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