Accuracy of intrapartum cardiotocography in identifying fetal acidemia by umbilical cord blood analysis in low-risk pregnancies

Tomich, Michaela Franco; Leoni, Renato Silva; Meireles, Pedro Teixeira; Petrini, Caetano Galvão; Araujo Júnior, Edward; Peixoto, Alberto Borges

doi:10.1590/1806-9282.20221182

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Revista da Associação Médica Brasileira

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Original Article • Rev. Assoc. Med. Bras. 69 (6) • 2023 • https://doi.org/10.1590/1806-9282.20221182 copy

Accuracy of intrapartum cardiotocography in identifying fetal acidemia by umbilical cord blood analysis in low-risk pregnancies

Authorship SCIMAGO INSTITUTIONS RANKINGS

SUMMARY

OBJECTIVE:

The aim of this study was to evaluate the accuracy of intrapartum cardiotocography in identifying fetal acidemia by umbilical cord blood analysis in low-risk pregnancies.

METHODS:

This is a retrospective cohort study of low-risk singleton pregnancies in labor after performing intrapartum cardiotocography categories I, II, and III. The presence of fetal acidemia at birth was identified by analyzing the pH of umbilical cord arterial blood (pH<7.1).

RESULTS:

No significant effect of the cardiotocography category on the arterial (p=0.543) and venous (p=0.770) pH of umbilical cord blood was observed. No significant association was observed between the cardiotocography category and the presence of fetal acidemia (p=0.706), 1-min Apgar score <7 (p=0.260), hospitalization in the neonatal intensive care unit (p=0.605), newborn death within the first 48 h, need for neonatal resuscitation (p=0.637), and adverse perinatal outcomes (p=0.373). Sensitivities of 62, 31, and 6.0%; positive predictive values of 11.0, 16.0, and 10.0%; and negative predictive values of 85, 89.0, and 87.0% were observed for cardiotocography categories I, II, and III, respectively.

CONCLUSION:

The three categories of intrapartum cardiotocography presented low sensitivities and high negative predictive values to identify fetal acidemia at birth in low-risk pregnancies.

KEYWORDS:
Pregnancy outcomes; External cardiotocography; Fetal blood; Blood gas analyses

		Category I (n=90)	Category II (n=30)	Category III (n=10)	p
Age (years)		24.0 (21.0–24.0)	22.5 (17.0–26.0)	22.5 (16.0–25.2)	0.080^† † median (interquartile range); one-way ANOVA
Ethnicity
	White	31.1% (28/90)	53.3% (16/30)	60.0% (6/10)	0.110^§ § percentage (n/N); A: category I vs. category II; B: category I vs. category III; p<0.05.
	Black	14.4% (13/90)	6.7% (2/30)	0.0% (0/10)
	Mixed	51.1% (46/90)	40.0% (12/30)	30.0% (3/10)
	Asiatic	3.3% (3/90)	0.0% (0/30)	10.0% (1/10)
Smoking		8.9% (8/90)	13.3% (4/30)	10.0% (1/10)	0.781^§ § percentage (n/N); A: category I vs. category II; B: category I vs. category III; p<0.05.
Number of pregnancies		1.9 (1.3)^B	1.7 (1.0)	1.1 (0.3)	0.043^∫ ∫ mean (standard deviation); chi-Square
Number of deliveries
	Nulliparous	1.1% (1/90)	0.0% (0/30)	0.0% (0/10)	0.799^§ § percentage (n/N); A: category I vs. category II; B: category I vs. category III; p<0.05.
	Multiparous	98.9% (89/90)	100% (30/30)	100% (10/10)
Gestational age (weeks)		40.0 (38–40)	39.5 (38–40)	39.5 (37.2–40.2)	0.808^† † median (interquartile range); one-way ANOVA
Type of delivery
	Vaginal	83.3% (75/90)^A,B	30.0% (9/30)	20.0% (2/10)	<0.001^§ § percentage (n/N); A: category I vs. category II; B: category I vs. category III; p<0.05.
	Cesarean section	13.3% (12/90)^A,B	70.0% (21/30)	80.0% (8/10)
	Forceps	3.3% (3/90)	0.0% (0/30)	0.0% (0/10)
Birth weight (g)		3220.0 (474)	3137 (439)	3117 (543)	0.605^∫ ∫ mean (standard deviation); chi-Square
Apgar score at 1st minute		8.5 (8.0–9.0)^B	8.0 (8.0–9.0)	8.0 (8.0–9.0)	0.037^† † median (interquartile range); one-way ANOVA
Apgar score at 5th minute		9.5 (9.0–10.0)^B	9.0 (9.0–9.0)	9.0 (8.0–9.0)	0.017^† † median (interquartile range); one-way ANOVA
Time cord clamping and pH analysis		13.9 (3.6)	14.2 (3.3)	16.6 (4.2)	0.506^∫ ∫ mean (standard deviation); chi-Square
pH arterial		7.24 (7.19–7.28)	7.21 (7.17–7.28)	7.22 (7.20–7.29)	0.543^† † median (interquartile range); one-way ANOVA
pH venous		7.29 (7.25–7.34)	7.29 (7.21–7.33)	7.27 (7.23–7.34)	0.770^† † median (interquartile range); one-way ANOVA

		Category I (n=90)	Category II (n=30)	Category III (n=10)	p
Indications of CTG
	Bleeding	8.9% (8/90)	6.7% (2/30)	20% (2/10)	0.442
	FHR abnormality	12.2% (11/90)^A	30.0% (9/30)	20.0% (2/10)	0.047
	Misoprostol use	30.0% (27/90)	23.3% (7/30)	30.0% (3/10)	0.777
	Oxytocin use	37.8% (34/90)	26.7% (8/30)	30.0% (3/10)	0.514
	Temperature>38°C	2.2% (2/90)	0.0% (0/30)	0.0% (0/10)	0.637
	Meconium	8.9% (8/90)	13.3% (4/30)	0.0% (0/10)	0.442
Adverse perinatal outcomes
	Acidemia at birth	11.1% (10/90)	16.7% (5/30)	10.0% (1/10)	0.706
	Apgar score 1st minute<7	6.7% (6/90)	13.3% (4/30)	20.0% (2/10)	0.260
	Admission at neonatal ICU	10.0% (9/90)	13.3% (4/30)	20.0% (2/10)	0.605
	Need for neonatal resuscitation	2.2% (2/90)	0.0% (0/30)	0.0% (0/10)	0.637
	Composite perinatal outcomes	21.1% (19/90)	20.0% (6/30)	40.0% (4/10)	0.373

	OR (95%CI)	Sensibility	Specificity	PPV	NPV	FP	FN	LHR negative	LHR positive
Category I	0.70 (0.25–2.16)	0.62	0.29	0.11	0.85	0.71	0.38	1.31	0.87
Category II	1.61 (0.57–4.80)	0.31	0.78	0.16	0.89	0.22	0.69	0.88	1.41
Category III	0.77 (0.06–5.79)	0.06	0.92	0.10	0.87	0.08	0.94	1.02	0.75

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[1] *Corresponding author: araujojred@terra.com.br