Admission Cardiotocography Effective Noninvasive tool for Screening High Risk Pregnancy: IJOGR
In India 20-30% pregnancies belong to high risk category which is responsible for perinatal morbidity and mortality. To prevent this lead to the introduction of Admission Cardiotocography (CTG). It is a non-invasive, brief fetal heart rate recording procedure immediately after admission to the labor ward that forecasts hypoxia encountered in intrapartum period. Hypoxial injuries caused by stress and contractions during childbirth are endured by the fetus. The prime reason for CTG admission test is that uterine contractions minimise placental blood flow during childbirth and unusual tracing reflects inadequacy and thus suggests fetal compromise in order to facilitate intervention at an early point.
The NICE guidelines 2017 do not propose CTG in low-risk women but suggests admission CTG for high-risk cases. A study was carried by Nity and Das at a tertiary care centre to evaluate the correlation between the labor admission test and adverse perinatal outcome in high risk pregnancy.
A prospective observational study was carried out in 230 pregnant women with high risk pregnancy in KIMS BBSR, Odisha during period of 2018-2020 who were admitted to labor room with gestational age more than 33 weeks for continuous FHR monitoring with CTG (cardiotocography) for 20 minutes.
Definition of CTG tracings (NICE guidelines 2017):
Normal: An HR trace in which features are classified as reassuring.
Suspicious: An FHR trace with 1 no reassuring feature AND 2 reassuring features.
Pathological: An FHR trace with 1 abnormal feature OR 2 no reassuring features.
Patients with a normal reactive test were assessed by periodic auscultation for a minute, every half an hour in the first stage of labor and every 5 minutes in the second stage of labor. Continuous CTG recordings were applied to women who had suspicious tracings. Fetal outcome were noted in terms of Live birth, Still birth, Weight of the baby, APGAR score (Appearance, Pulse, Grimace, Activity, Respiration), NICU admission, Neonatal seizure and Maternal outcome in terms of NVD and LSCS. (Normal vaginal delivery and Lower segment cesarean section)
- Among 230 patients majority of them were primigravida in age group of 21-25 years. Pathological Admission test was higher in age more than 30 years.
- The admission test were normal in (68.7%), suspicious in (21.7%) and pathological in (9.6%).
- Out of 158 (68.7%) patients with normal admission test, 21 (13.3%) patients were associated with fetal distress. A higher percentage of fetal distress was observed in suspicious AT (26%) and the pathological AT showed significantly higher incidence of fetal distress (54.5%) as per Chi-Square test (p<0.05).
- The incidence of fetal distress, meconium stained liqour, NICU (Neonatal Intensive Care Unit) admission and APGAR score less than 7 was significantly higher with pathological AT as compared with suspicious and normal AT.
- LSCS (Lower segment cesarean section) was done in majority in the pathological admission test group (65%), followed by suspicious (40.4%), and normal (30.1%) respectively and incidence of instrumental delivery was higher with normal admission test patients (13.5%), followed by Pathological admission test (10%) and suspicious admission test (6.4%) respectively. Normal spontaneous vaginal delivery was higher in normal admission test group (56.4%).
- The most common risk factor in this study was postdated (39.1%) followed by Gestational Hypertension (GH) (21.1%), Premature Rupture of the Membranes(PROM) (10.4%), Bad Obstetric History (BOH) (6.9%), GH with IUGR (Intrauterine Growth Restriction) (6.5%), IUGR (5.6%), Oligohydramnios (4.3%), Diabetes (3.5%) and Rh negative pregnancy (2.6%).
Labor is a troublesome process continuous monitoring of fetal heart rate by electronic fetal monitoring is crucial during this time. So Admission test is necessary. It is a screening test for the state of oxygenation of fetus on admission. It evaluates the placental reserve by checking the response of fetal heart during the phase of temporary occlusion of utero placental blood flow during uterine contraction. Hence, it checks the ability of fetus to endure the process of labor.
Therefore, the admission CTG has 2 possible functions:
- It can be used in early labor as a screening test to identify distressed fetuses on admission.
- Identify women who need regular fetal monitoring.
In present study, Labor admission test has high sensitivity (52.71%), specificity (74.87%) and Negative predictive value (NPV) (85.57%) for predicting fetal distress. The proportion of false negatives were low (10.3%). The sensitivity and specificity of the admission test were good when benign fetal outcomes like development of fetal distress during labor were excluded in favor of more ominous fetal outcomes like severe asphyxia at birth and neonatal ICU admissions.
The authors concluded, "The admission cardiotocography test is an easy, noninvasive, economical measurement of both antepartum and intrapartum fetal well being. It is a precise screening modality to distinguish and separate high risk from low risk patients. Admission test in intrapartum surveillance detects fetal distress if already present at admission and predicts fetal well-being for the next few hours (5-6 hrs) unless interfered by an acute event (eg-cord prolapse, abruptio placenta). As most patients with a pathological tracing eventually ended up in Caesarean delivery, the role of AT in preparing for early intervention is crucial. The load of constant monitoring in high risk patients can be decreased thus proving to be a time saving method in intervention required especially in institutes with a high patient load. After CTG screening obstetrician should be able to assess that fetus is healthy and needful intervention can be taken."
Source: Nity and Das / Indian Journal of Obstetrics and Gynecology Research 2021;8(2):158–161