. 2023 Jun 5;12:e44430. doi: 10.2196/44430

Table 4.

Heart rate variability (HRV) components in pregnancy complications, with the difference in HRV based on the majority of studies.

Pregnancy complications			Linear HRV component in the frequency domain (FD)															Linear HRV component in the time domain (TD)									Nonlinear HRV component
			HF^a		LF^b (nu)		LF		HF (nu)		LF/HF		LF/HF (ln)		VLF^c		TP^d			SDNN^e		RMSSD^f		SDANN (ln)		Entropy
GDM^g (4 of 5 studies)			Not significant^h		Not significant^h		Not significant^h		Not significant^h		Not significant^h		Not significant^h		Not significant^h		Not significant^h			Not significant^h		Not significant^h		Not significant^h		Not significant^h
Impaired fetal growth (4 of 4 studies)			—ⁱ		—		—		—		—		—		—		—			—		Increased		—		—
Hypertensive disorders (n=1) that were reviewed in 24 studies
	GH^j (n≥12)	Decreased		Increased		—		—		—		Increased		—		Decreased			Decreased		Decreased		—		—
	Preeclampsia (n≥12)	Decreased		Increased		—		Decreased		Increased		Increased		—		—			Decreased		—		Increased		—
	HPD^k (n≥12)	Not significant^h		Not significant^h		Not significant^h		Not significant^h		Not significant^h		Not significant^h		Not significant^h		Not significant^h			Not significant^h		Not significant^h		Not significant^h		Not significant^h
Pulmonary function (n=2)
	Low FEV1/FVC^l (n=1)	—		—		—		—		Increased		—		—		—			—		—		—		—
	Amniotic fluid embolism (n=1)	—		—		—		—		—		—		—		—			—		—		—		Decreased
Central nervous system (n=1)
	Grand mal seizure	—		—		Decreased		—		—		—		Increased		—			—		—		—		—

^aHF: high frequency.

^bLF: low frequency.

^cVLF: very low frequency.

^dTP: total power.

^eSDNN: standard deviation of the normal-to-normal R-R intervals.

^fRMSSD: root mean square of successive differences between normal heartbeats.

^gGDM: gestational diabetes mellitus.

^hThe common biomarkers in the majority of the studies showed no significant difference from the controls.

ⁱNot assessed by the majority of the studies.

^jGH: gestational hypertension

^kHPD: hypertensive disorders

^lFEV1/FVC: forced expiratory volume at 1 second to forced vital capacity.