Role of admission cardiotocography in predicting the obstetric outcome in term antenatal women: A prospective observational study

Inclusion criteria: All pregnant women (primigravida/ multigravida) with live, singleton, term pregnancy (gestation ≥ 37 weeks) with cephalic presentation admitted to the labour ward in their first stage of labour (spontaneous in onset) were included as study participants. They were divided into high- and low-risk cases based on the presence or absence of risk factors, including anemia, hypertensive disorders of pregnancy, Rh isoimmunization, medical disorders (diabetes, thyroid disorders, renal disease), post-dated, oligo/polyhydramnios, fetal growth restriction and prelabour rupture of membranes.

Exclusion criteria:

Sampling Procedure: Consecutive sampling of participants fulfilling the inclusion criteria was done for the entire duration of the study.

Data collection: After informed written consent from all the participants in their vernacular language, various sociodemographic parameters such as age, religion, occupation, registration status, gravidity, parity, number of live children and current gestational age were recorded on a preformed data collection sheet by trained nursing staff. A detailed medical, surgical and family history of all the participants was recorded, followed by a thorough physical examination including abdominal and vaginal examination to confirm the gestation, presentation and stage of labour. Depending on the presence or absence of high-risk factors mentioned in the inclusion criteria, the participants were divided into two groups: Group I – Term antenatal women with high-risk pregnancy and Group II – Term antenatal women with low-risk pregnancy. The participants in both groups were then subjected to admission CTG for 20 minutes at a speed of 1cm/min. It was done in a separate room with the patient lying in a semi-lateral position. The FHR tracings thus obtained were categorised according to the National Institute for Clinical Excellence clinical guidelines [7] as:

Women with reactive tracing were monitored by either intermittent auscultation every 30 minutes in the first stage and every 5 minutes in the second stage of labour or with continuous cardiotocograph. The women with suspicious tracing were monitored with continuous cardiotocograph, and any abnormal FHR tracing with significant decelerations (variable or prolonged deceleration), baseline FHR < 110bpm or > 160bpm with loss of variability, were considered as having fetal distress and were delivered by either instrumental delivery or by emergency cesarean section. The colour of the liquor, mode of delivery, neonatal Apgar scores at one and five minutes, neonatal birth weight, need for neonatal resuscitation and neonatal intensive care unit (NICU) admission were recorded in the datasheet. Results of the admission CTG test were then compared with various labour outcome variables, including the incidence of fetal distress, overall neonatal, maternal outcomes, and the efficacy of the admission test in predicting perinatal outcomes in both low- and high-risk pregnancies.

Statistical analysis of data was performed using Statistical Package for Social Sciences (SPSS) software version 21.0. Categorical variables were presented as numbers and percentages (%) and continuous variables as mean ± SD and median. Qualitative variables were correlated using the Chi-Square test. The diagnostic test was used to calculate sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV). A p-value of < 0.05 was considered statistically significant.

The present research involving human subjects was conducted following the ethical standards of all applicable national and institutional committees and the World Medical Association’s Helsinki Declaration. It was conducted after informed written consent from the participants and ethical approval from the Institutional Ethical Committee (IEC number: 2015/571).

Sociodemographic outcomes: Of 100 term antenatal women admitted to the labour ward in the first stage of labour, 51 were low-risk and 49 were high-risk pregnancies. The common high-risk factors observed were hypertensive disorders of pregnancy (20.4%), anemia (20.4%), seizure disorders other than eclampsia (20.4%), gestational diabetes mellitus (16.3%), Rh-incompatibility (8.2%), oligohydramnios (6.1%), fetal growth restriction (4.1%) and post-date (4.1%). The mean age and gestation of women at the time of admission were 24.76 ± 2.98 years and 38.83 ± 1.09 weeks, respectively. The majority of the participants were multigravida (57%), and around 55% were booked. The various sociodemographic features of the participants are depicted in Table 1.

Obstetric outcome: In the low-risk group, a total of 47 women had reactive, two (3.9%) suspicious and two (3.9%) ominous FHR tracing, whereas in the high-risk group, 20 (40.8%) participants had reactive, 16 (32.6%) suspicious, and 13 (26.5%) ominous FHR tracing on admission CTG (p < 0.0001), indicating the crucial role of admission CTG in the detection of fetal distress, especially in high-risk pregnancies. Of the total 100 participants, only five (5%) had meconium-stained fluid. The correlation between the colour of liquor and CTG results in both low- and high-risk pregnancies is depicted in Table 2. It was observed that the majority of participants with clear liquor had reactive CTG in both groups, whereas participants with meconium-stained fluid either had suspicious or ominous FHR tracing on CTG (p < 0.05). The majority of participants in both the groups with reactive CTG had a normal vaginal delivery (56%), and all the participants with ominous CTG tracing had an emergency cesarean section (100%). The association between the admission CTG results and the mode of delivery in the low-and high-risk group is depicted in Table 3.

Perinatal outcome: Of the total 100 neonates delivered to all the participants, the mean birth weight of all was 2.85 Kg. No significant correlation was observed between the admission test results and neonatal birth weight in both low- and high-risk groups. The correlation between one and five minutes of Apgar scores, neonatal resuscitation, NICU admission and admission CTG results is depicted in Table 4. A statistically significant correlation was observed between abnormal CTG results and adverse neonatal outcomes, including poor Apgar scores, need for neonatal resuscitation and NICU admission in both groups. The comparison of sensitivity, specificity, NPV and PPV of admission CTG in the prediction of neonatal outcomes between low- and high-risk pregnancies is depicted in Table 5. It was observed that the admission test has high specificity and NPV in the prediction of fetal distress in both low- and high-risk participants.

The present study was conducted for a short duration and with limited sample size. The number of high-risk cases included in the study was only 49. In the future, we can plan to conduct a multicentric study with a large sample size of only high-risk pregnant women. Furthermore, we will include fetal blood sampling to confirm fetal hypoxia before planning for emergency operative delivery, so as to reduce the risk of unnecessary cesarean sections.

Key Points