Table 3 Findings of NIEA parameters in studies utilising non-invasive fetal electrocardiogram

1981

Karinemi et al.

STV using DI

95.4% of NIFECG were successfully acquired. The distribution of DI in the IUGR group was significantly different to the normal cohort (p < 0.001). DI had sensitivity of 64% and predictive value of 80% in screening for fetal distress in the IUGR group(p < 0.01)

1982

Brambati et al.

QRS

100% of NIFECG were successfully analysed 96.2% of SFD fetuses had QRS duration less then 2SD below the normal values for gestation. QRS duration (in pregnancy) and live birthweight demonstrated a strong relation (r = 0.74, p < 0.001)

1986

Pardi et al.

QRS

100% of NIFECG were successfully analysed. 81.5% of IUGR fetuses had QRS duration less then 2SD below the normal values for gestation. QRS duration (in pregnancy) and live birthweight demonstrated a linear relation (r = 0.69, p < 0.001) QRS values >4SD below normal were related with abnormal CTG, low APGAR and perinatal deaths

2012

Graatsma et al.

FHR PRSA- AC/DC STV

STV increased in early gestation with stable 3rd trimester values AC and DC remained constant during pregnancy irrespective of gestation. STV abnormal in 16% of the IUGR fetuses AC and DC abnormal in 36 and 40% of IUGR Z scores for IUGR fetuses for STV, AC and DC were lower by 1.0SD, 1.5SD and 1.7SD respectively in comparison to the controls [mean of z- scores, 0;SD-1, (p < 0.0001)] In IUGR group, AC and DC z scores were lower than STV scores. When STV z score was utilised with AC and/or DC Z-scores, the findings of deviation became more accentuated

2015

Stampalija et al.

PRSA STV

Significantly lower AC and DC in IUGR vs controls (p < 0.05) for any T ≥ 5 values AUC for AC [0.63 (95% CI 0.47–0.78)–0.87 (95% CI 0.77–0.96)] and DC [0.64 (95% CI 0.48–0.79)–0.89 (95% CI 0.81–0.98)] STV significantly lower between IUGR and controls (8.6 ± 2.4vs 11.1 ± 2.6 ms. P = 0.001). AUC for STV 0.77 (95% CI 0.65–0.90). AUC for PRSA significantly outperformed STV

2016

Stampalija et al.

PRSA- AC/DC at T9

AC and DC at T9 were significantly lower in IUGR vs controls after adjusting for GA [OR = 2.1, 95%CI 1.5–3.0 and OR = 0.5 95%CI 0.36–0.68, p < 0.001) AC and DC at T9 were higher for IUGR with brain sparing vs those without brain sparing (OR = 1.8, 95%CI 0.97–3.4, p = 0.06 and OR = 0.5 95%CI 0.30–0.98, p = 0.04)

2016

Fuchs et al.

T/QRS ratio STV FIGO classification of CTG- normal, suspicious and pathological

STV in normal pregnancies (9.08 ± 3.91) were significantly different (p < 0.05) from IUGR with brain sparing (11.33 ± 1.38) and IUGR without brain sparing (10.16 ± 4.98) T/QRS values were all below the cut off for abnormal results across all groups Highest average T/QRS ratio (> 0.3) seen in IUGR with brain sparing regardless of FIGO classification of CTG No correlation found between T/QRS ratio and FIGO classification of CTG

2016

Fuchs et al.

T/QRS ratio

Regression did not show any significant differences between groups in relation to GA and T/QRS ratio. T/QRS ratios demonstrated significant differences between IUGR group with reduced CPR and normal CPR (p < 0.001) When using the maximum values and maximum – minimum values, the regression line descends in group with normal CPRs but rises in group with reduced CPR.

2017

Velayo et al.

QT, RR, QRS, ST,PR and PQ intervals. QTc, PR/RR and HR

100% of PQRST were recognised. Both QT and QTc parameters were significantly prolonged (p < 0.05). QT > 267.99 has a sensitivity of 80.0% and a PPV of 40% for IUGR. QTc > 0.43 had a sensitivity > 86.7% and PPV of 40.6%.