Table 3.
Included studies, characteristics and outcome.
| Population | Method | Outcomes | |||||||
|---|---|---|---|---|---|---|---|---|---|
| References | Nfetus/Nrecord | GA in weeks | Hz | Mode of fetal movement | Fetal movement detection | Analysis | Length of time series | Measure/unit | Short description |
| Wheeler et al. (1980) | 21/34 | 36–41 | 10,000 | Breathing/non-breathing Active/rest | UL | Time domain | Unclear /1-min epochs | RR-interval/ms | SDNN was higher in breathing and active episodes compared to non-breathing and rest. No change in mean RR. |
| Divon et al. (1985) | 15/60 | 38–41 | ? | Breathing/non-breathing | UL | Spectral | Unclear/1-min epochs | RR-interval/spectral density | A density peak in 0.7–0.95 Hz during breathing. Frequency range identical with breathing frequency. Spectral densities slightly elevated between 0.7 and 1.05 Hz during non-breathing. |
| Ohno et al. (1986) | 4/32 | 36–41 | ? | Breathing/non-breathing | UL | Time domain | 256 beat epochs | RR-interval/ms | SDNN was higher in breathing compared to non-breathing. The percentage of beat-to-beat differences below 2 ms, was lower during breathing. No difference in mean heart rate. |
| Ferrazzi et al. (1989) | 4/4 | 26/36 | 1,024 | Breathing/non-breathing | UL | Spectral | 256 beat epochs | RR-interval/s | A HF peak around 0.7–0.9 Hz was seen during breathing in GA 36, not in GA 26. |
| Groome et al. (1994) | 13/81 | 36–40 | 833 | Breathing/non-breathing | UL | Spectral | 3 min | RR-interval/no units | Total power, VLF, LF and HF power were higher in epochs of breathing compared to non-breathing in the quiet FBS (1F). 85% had a prominent HF peak during breathing and 54% in non-breathing, both in quiet FBS (1F) |
| Frank et al. (2006) | 39/39 | 35–40 | 1,000 | Active/rest | FBS | Time domain Spectral Entropy |
5 min | RR-intervals/ms | Active FBS (2F, 4F) was associated with higher variability compared to the less active state (1F) including higher SDNN, RMSSD, ln(LF), ln(HF). ApEnsub decreased with fetal activity (1F vs. 4F) While ApEnpop increased from 1F to 2F. however, unchanged from 1F to 4F. |
| Gustafson et al. (2011) | ?/43 | 36–38 | 300 | Breathing/non-breathing | dMMG/FBS | Time domain Spectral |
Varied from 60 to 144 s | RR-interval/ms | RMSSD and HF were higher in breathing epochs compared to non-breathing epochs in active FBS (2F, 4F). LF/HF and heart rate were lower in breathing epochs compared to non-breathing |
| Ortiz et al. (2013) | 12/26 | 34 (±3.7) | 500 | ≤ 40% breathing/ <40% non-breathing | UL | Time domain Spectral |
5 min | RR-interval/ms | HF and RMSSD were higher during breathing. Both RMSSD and HF, in the group with <40% breathing, showed a significant linear correlation with RR intervals. Both increasing with increasing RR-interval. No significant linear correlation in the group with breathing ≥40 % No difference in Mean RR in the two groups. |
| Gustafson et al. (2012) | 15/15 | >36 | 300 | Breathing/non-breathing | dMMG/FBS | Time domain Spectral |
Varied from 60 to 140 s | RR-intervals/ms | Fetal breathing resulted in significantly higher Log (HF), log(RSA), Log (RMSSD) and lower log(LF/HF) compared to non-breathing. All analyzed in FBS 2F+3F. Fetal heart rate was lower during breathing movements. |
| van Laar et al. (2014) | 25/25 | 34–41 | 1,000 | Active/rest | UL/FBS | Spectral | 64 s epochs | RR-interval/ms | Total power, LFabsolute and LFnormalized were significantly higher in the active state compared to resting state. HFabsolute also increased but not significantly. HFnormalized was lower in the active state compared to resting state. |
| Brändle et al. (2015) | 55/55 | 24–41 | 1,221 | Active/rest | FMCG/FBS | Time domain Entropy |
256 beats (moving window) | RR-interval/no units | Mean heart rate, RMSSD and (SDNN/RMSSD) increased with increasing activity from week 32. SDNN increased with increasing activity trough all gestational ages. |
| Arias-Ortega et al. (2016) | 10/10 | 34.2 (± 2.6) | 1,000 | Breathing/non-breathing | UL | Time domain Spectral |
30 s epochs | RR-interval/ms | Higher mean RR and RMSSD in fetal breathing compared to non-breathing. |
| Stone et al. (2017) | 29/29 | 36–38 | 2,200 | Active/rest | FBS | Time domain | 1 min | RR-intervals/ms | SDNN and RMSSD were significantly higher in 2F compared with 1F and 4F. SDNN/RMSSD increased from 1F to 2F and from 2F to 4F. FHR was higher in 4F compared with 2F and in 2F compared with 1F. |
| Zavala et al. (2019) | 22/22 | 36–39 | 300–900 | Active/rest | FBS/AC | Time domain | 30 s epochs | RR-intervals/ms | SDNN was significantly higher in 2F compared with 1F. In RMSSD a trend toward higher mean in 2F compared with 1F was observed (p = 0.09). No difference in FHR in state 2F and 1F. |
GA, Gestational age; UL, Real time doppler ultrasound; FBS, Fetal behavioral state defined by Nijhuis et al. (1982); dMMG, Magnetomyography; FMCG, Fetal magnetocardiography (changes in orientation of fetal heart vectors); AC, Fetal actocardiography.