- Received November 30, -0001
- Accepted November 30, -0001
- Publication June 15, 2020
- Visibility 6 Views
- Downloads 1 Downloads
- DOI 10.18231/j.ijogr.2020.042
-
CrossMark
- Citation
Role of non stress test in monitoring antenatal fetal well being in high risk pregnancy
- Author Details:
-
Praveen Kumar Choudhary
-
Balgopal Singh Bhati *
-
Sunita Bishnoi
Introduction
A high risk pregnancy is one in which some conditions put the mother, the developing fetus, or both at higher than normal risk for complications during or after the pregnancy and birth. Antepartum evaluation of the fetus at risk for damage or death in utero remains a major challenge in modern obstetrics.
According to American College of Obstetrician and Gynaecologists and American Academy of Pediatrics (2012)[2] the objectives of antepartum fetal surveillance are to prevent fetal death and avoidance of unnecessary intervention.[1]
The test is named “non-stress” because no stress is placed on the fetus during test. Among all available tests this is simple to be done, can be repeated, non-harmful, cost effective, handy and low maintenance. It is most widely used primary testing method for assessment of fetal well-being.
| Features | Baseline FHR | Variability | Deceleration | Acceleration |
| Reassuring | 110-160 bpm | >5 bpm | None | Present |
| Non reassuring | 100-109 bpm 161-180 bpm | <5 bpm for >40 min but <90 min | Early deceleration Typical Variable deceleration Single prolonged deceleration ≤ 3 min | Absence of acceleration with an otherwise normal CTG is of uncertain significance |
| Abnormal | <110 >180bpm sinusoidal pattern for ≥10 min | <5 bpm for >90 min | Atypical variable deceleration Late deceleration Single prolonged deceleration > 3 min |
Basic pattern recognition and interpretation
Characteristic of normal heart rate pattern.
Baseline heart rate-110-160bpm.
Baseline variability > 5bpm.
No of acceleration > 2 in 20 min period.
No of deceleration-absent or early deceleration.
Fetal outcome: vigorous with Apgar score > 7.
Interpretation
Reassuring: Two or more FHR acceleration of 15 bpm for 15 seconds in 20 min usually associated with episodes of fetal movement and normal baseline variability more than 5 bpm.
Non-reassuring: any tracing with no FHR acceleration or inadequate acceleration that is less than 15 bpm or a tracing with decreased FHR variability.
Sinusoidal: super imposed or non-reassuring pattern. It is smooth undulating FHR pattern with a frequency of 2-5 cycles/min. Long Term variability and amplitude of 5-15 beats/min with the absence of acceleration or fixed or flat short term variability. Oscillation of sinusoidal waves from above or below the baseline.
Unsatisfactory: tracing not adequate for interpretation.
Salutatory: rapidly recurring couplets of acceleration and deceleration causing relatively large oscillation of baseline FHR.
Materials and Methods
The present prospective study was conducted in department of Obstetrics & Gynaecology, Umaid hospital, Jodhpur from period of July 2015 to December 2015. The study was done on 100 cases. 50 high risk pregnancies were taken randomly as study group and 50 normal pregnancy cases were taken randomly as control group. The subjects were explained the test, need of the test, done after 28 weeks of gestation.
Inclusion criteria
Pregnancy complicated by
Hypertensive disorders -Pre-eclampsia and chronic hypertension, Diabetes complicating pregnancy, including gestational diabetes (GDM), Intra-uterine growth retardation (IUGR), Post dated pregnancy, Liquor abnormalities, Recurrent pregnancy losses (RPL), Pregnancy with previous cesarean section, Multiple gestation, Pregnancy with medical illness, Loss or decreased fetal movements, Rh isoimmunization and Anemia.
Exclusion criteria
Pregnancy with gestational age <28 weeks, Antepartum hemorrhage, Eclampsia, Congenital anomalies, Intrauterine fetal death (IUFD).
Method
Testing protocol for NST
Equipment: electronic fetal-maternal monitor.
FHR: Doppler signal source (Piezo-electric effect).
Uterine contraction: External tocodynamometer + manual palpation.
Fetal Movement: Remote event marker + observer confirmation.
Maternal position: semi-Fowler's, lateral hip displacement.
Baseline observation period: 20 min.
Maternal fed state: 2 hr postprandial.
Maternal activity: 2 hr sedentary.
No smoking; sedative drug within 2 hr.
Observations and Results
Study (high risk) and Control (healthy) group each had 50 cases.
| Study group | No. of patients | Percentages |
| Hypertensive disorders | 17 | 34% |
| Oligohydramnios | 14 | 28% |
| IUGR | 9 | 18% |
| Decreased or Loss of fetal movements | 6 | 12% |
| Fetal hypoxia | 6 | 12% |
| GDM | 4 | 8% |
| Heart disease | 4 | 8% |
| Previous cesarean | 4 | 8% |
| Multiple gestation | 2 | 4% |
| Recurrent pregnancy losses | 2 | 4% |
| Rh Isoimmunization | 2 | 4% |
| Precious pregnancy | 2 | 4% |
| Hemoglobinopathy | 1 | 2% |
| Postdatism | 1 | 2% |
| Jaundice | 1 | 2% |
| Types of cases | No. of patients | Percentages |
| PIH | 5 | 10% |
| GDM | 4 | 8% |
| Oligohydramnios with IUGR | 4 | 8% |
| Oligohydramnios | 3 | 6% |
| Decreased fetal movements | 3 | 6% |
| PIH with oligohydramnios | 3 | 6% |
| Fetal hypoxia | 3 | 6% |
| Heart disease | 3 | 6% |
| Severe pre eclampsia | 2 | 4% |
| Multiple gestation with PIH | 2 | 4% |
| Previous cesarean with UPI | 2 | 4% |
| Precious pregnancy with oligohydramnios with IUGR | 1 | 2% |
| Postdatism with PIH | 1 | 2% |
| Recurrent pregnancy losses | 1 | 2% |
| PIH with RPL | 1 | 2% |
| Previous cesarean with decreased fetal movement | 1 | 2% |
| Previous cesarean, IUGR, oligohydramnios | 1 | 2% |
| Oligohydramnios with decreased fetal movement | 1 | 2% |
| Heart disease with IUGR | 1 | 2% |
| Fetal hypoxia with IUGR | 1 | 2% |
| Rh isoimmunization with IUGR with eclampsia | 1 | 2% |
| PIH with IUGR | 1 | 2% |
| Hemoglobinopathy | 1 | 2% |
| Rh isoimmunization with pre eclampsia | 1 | 2% |
| Jaundice | 1 | 2% |
| Loss of fetal movement | 1 | 2% |
| Precious pregnancy with oligo | 1 | 2% |
PIH, GDM and oligohydramnios with IUGR are commonest.
| Age (Years) | Control group | Study group | Non-reassuring NST (Study group) |
| 18-22 | 14 (28%) | 16 (32%) | 2 (12.5%) |
| 23-26 | 23 (46%) | 21 (42%) | 5 (23.8%) |
| 27-30 | 12 (24%) | 11 (22%) | 2 (18.18%) |
| 31-34 | 1 (2%) | 2 (4%) | 0 (0%) |
Most of the patients belong to 23-26 years age group as this is peak reproductive age group.
| Gravida | Control group | Study group |
| Primigravida | 26 (52%) | 30 (60%) |
| Multigravida | 20 (40%) | 16 (32%) |
| Grand multigravida | 4 (8%) | 4 (8%) |
Majority of patients are primi gravid.
| S. No. | Obstetric complication | Gestational age | NST Impression | Birth asphyxia | Mode of delivery | Duration of nursery stay |
| 1 | Severe pre eclampsia | 32 Wks | Reassuring | Present | Vaginal delivery | 19 days (LBW 1.47kg) |
| 2 | Previous LSCS with decreased fetal movements | >37 Wks | Reassuring | Present | Elective LSCS | 2 days Then mother shifted |
| 3 | Prev LSCS with s. oligo withs. IUGR | 28 Wks | Reassuring | Present | LSCS (Scar dehiscence) | 29 days (LBW 1.1kg Baby expired) |
In study group, 3 patients had reassuring NST with abnormal perinatal outcome and diagnosis was severe pre eclampsia, previous cesarean with decreased fetal movement and previous cesarean with severe oligo with severe IUGR.
| Cases | Total | Perinatal morbidity | Perinatal mortality |
| Reassuring NST | |||
| Control | 50 (100%) | 0 | 0 |
| Study | 41 (82%) | 2 (4.87%) | 1 (2.44%) |
| Non-Reassuring NST | |||
| Control | 0 | 0 | 0 |
| Study | 9 (18%) | 2 (22.2%) | 1 (11.1%) |
Perinatal mortality and morbidity not shown in any of the patient in control group.
In study group 82% had Reassuring NST out of which 4.87% had perinatal morbidity while 2.44% had perinatal mortality. In study group 18% had non-reassuring NST out of which 22.2% had perinatal morbidity while 11.1% had perinatal mortality.
| S. No. | Obstetric complication | Gestational age | NST Impression | Mode of delivery | Indication of LSCS | Duration in Nursery Stay |
| 1 | Fetal hypoxia | >37 wks | Late deceleration | FTND | - | 2 Days |
| 2 | Prev. LSCS with UPI (fetal hypoxia) | 32 wks | Late deceleration | LSCS | Prev. LSCS with UPI | Expired on 14th day in nursery (severe birth asphyxia) |
| 3 | Fetal hypoxia | >37 wks | Late deceleration | FTND | - | - |
| 4 | Fetal hypoxia with IUGR | 36 wks | Late deceleration | FTND | - | - |
| 5 | Decreased fetal movements with 2LOC | >37 wks | Loss of variability | LSCS | Decreased fetal movements with 2LOC | - |
| 6 | Decreased fetal movement | 36 wks | Loss of variability | FTND | - | - |
| 7 | Fetal hypoxia | >37 wks | Prolonged deceleration | LSCS | Fetal hypoxia | 3 Days |
| 8 | Prev. LSCS with fetal hypoxia | >37 wks | Late deceleration | LSCS | Prev. LSCS with fetal hypoxia | - |
| 9 | Loss of fetal movement | >37 wks | Loss of variability | LSCS | Loss of fetal movement | - |
9 patients in study group had ominous NST pattern and 5 (55.5%) out of 9 had fetal hypoxia, 2 (22.2%) had decreased fetal movements, 1 (11.1%) had loss of fetal movement and uteroplacental insufficiency.
3 (33.3%) had gestational age less than 37 weeks while 6 (66.6%) had gestational age more than 37 weeks.
4 (44.4%) out of 9 delivered vaginally while 5 (55.5%) undergone LSCS.
2 (22.2%) had neonatal morbidity while 1 (11.1%) had neonatal mortality.
| Apgar Score | Control group | Study group |
| 10 | 7 | 3 |
| 9 | 39 | 32 |
| 8 | 4 | 9 |
| 7 | - | - |
| <7 | - | 6 |
In control group 7 new born had Apgar score of 10, 39 had score of 9 and 4 had score of 8. None in control group had low (<7) Apgar score. While in study group 3 new born had score of 10, 32 had score of 9, 9 had score of 8 and 6 had low apgar score.
| NST interpretation | Abnormal | Normal | Number |
| Non-reassuring | 3 | 6 | 9 |
| Reassuring | 3 | 38 | 41 |
| Total | 6 | 44 | 50 |
| Sensitivity | Specificity | Positive Predictive Value | Negative Predictive Value |
| 50% | 86.3% | 33.3% | 92.68% |
Discussion
During the past decades remarkably intimate knowledge of human fetus along with technological developments have prompted a new phenomenon in medicine of forecasting fetal health.
In present study focus is on contemporary testing procedures that depend on fetal heart rate.
In this decade characteristics of fetal heart rate testing has been used increasingly to predict the condition of fetus during antenatal period.
| Authors | Hypertensive disorders | IUGR | Decreased fetal movements | GDM | Post- datism | Previous LSCS | Rh incompatibility |
| Lee Drukker et al (1979) | 27.3% | - | 1.9% | 10.1% | 40.3% | - | 1.6% |
| Manning et al (1980) | 9.2% | 7.8% | - | 34% | 40.2% | - | 2.7% |
| Rayburn et al (1980) | 6% | 4.8% | - | 6% | 9.7% | - | - |
| Manning et al (1981) | 17.5% | 20.8% | 4.3% | 9.2% | 11.6% | 4.9% | 1.1% |
| Dastur et al (1981) | 22% | - | - | 1.6% | 10.1% | - | - |
| Phelan et al (1981) | 13.1% | 20.7% | 7% | 8.4% | 35.8% | - | 0.4% |
| Chamberlain (1984) | 20.5% | 18.4% | - | - | 15% | - | - |
| Hafizur Rahman et al (2012) | 20.6% | 11.3% | - | 3.1% | 42% | - | 4% |
| Dr P. Himabindu et al (2015) | 43% | 11% | - | 7% | 39% | - | 5% |
| Present study (2015) | 34% | 18% | 14% | 8% | 2% | 8% | 4% |
| Present study (2015) | Dr. P. Himabindu et al (2015) | Hafizur Rahman et al (2012) | |||
| Age(years) | No. of patients | Age(years) | No. of patients | Age | No. of patients |
| 18-22 | 30% | 18-20 | 23% | 17-20 | 13.12% |
| 23-26 | 44% | 21-25 | 50% | 21-25 | 42.5% |
| 27-30 | 23% | 26-30 | 23% | 26-30 | 31.25% |
| 31-34 | 3% | 31-35 | 4% | 31-40 | 13.13% |
| Gravida | Saadia Z (2015) | Hafizur Rahman et al (2012) | Present study (2015) | Dr. P. Himabindu et al (2015) |
| Primi gravida | 62% | 61.87% | 56% | 55% |
| Multi gravida | 37.9% | 38.13% | 36% | 41% |
| Grand multi gravida | - | - | 8% | 4% |
| Authors | No. of Patients | Low 5 minute Apgar score |
| Rochard (1976) | 125 | - |
| Kubli (low risk)1977 | 1320 | - |
| Visser (1977) | 434 | 3 |
| Flynn (1977) | 301 | 13 |
| Nochimson (1978) | 421 | - |
| Kubli (high risk) 1977 | 65 | 32 |
| Abhijit Biswas et al (2013) | 100 | 11 |
| Dr P. Himabindu et al (2015) | 100 | 17 |
| Present study (2015) | 100 | 6 |
| Authors | Sensitivity | Specificity | Positive Predictive Value | Negative Predictive Value |
| Neldam et al (1986) | - | 80% | 50% | - |
| Bhide AA et al (1990) | 65.64% | - | 23.12% | - |
| Hafizur Rahman et al (2012) | 60% | 94.8% | 56.8% | 88.6% |
| Abhijit Biswas et al (2013) | 72.7% | 72.7% | 30.7% | 94.1% |
| Dr. P. Himabindu et al (2015) | 82.3% | 80.7% | 46.6% | 95.7% |
| Present study (2015) | 50% | 86.3% | 33.3% | 92.68% |
Summary
The present study highlighted the following points:
21 (42%) patients in study group were of 23-26 years age group i.e. period of maximum reproductive capacity.
30 (60%) patients in high risk group were primigravida and most common (34%) high risk factor was hypertensive disorder in pregnancy followed by oligohydramnios (28%).
Non-reassuring NST was common (23 8% among 23-26 years age group and primigravida patients (23 3%).
Cesarean deliveries were common (18% among high risk group than control group (0%).
Perinatal morbidity and mortality was common (12%) among high risk group compared to study group (0%).
The sensitivity for perinatal morbidity and mortality was 50% i.e. NST detected 50% of all abnormal outcome.
The non-reassuring NST may be due to sleeping state, sedative drugs to mother, prematurity, chronic hypoxia or major congenital anomalies so before getting NST to be non-reassuring one should extend the duration of NST for another 20 min and should not hurry to intervene pregnancy rather should keep in mind the possible causes of non reactivity and manage accordingly.
Non stress test is easy to perform, informative, non invasive, reproducible, inexpensive, having no contraindication (if doubt can be repeated) but require proper logical interpretation for reliable prediction of outcome.
Antepartum fetal surveillance gave more reassurance to the obstetrician and decreased the number of hospital admission as well as the duration of hospital stays of many mothers.
None of new born in control group had low (<7) Apgar score while it was seen in 6 new born babies in study group. So fetal compromise is common in high risk pregnancy.
Conclusion
The ideal test for fetal reserve should be safe, inexpensive, readily available, quickly exerted and devoid of either false positive or false negative results. As yet no such test exists which is perfect, still NST has been shown to be most acceptable modality for evaluating the fetus in utero.
Until a perfect method is devised, the importance of judicious use and meticulous interpretation of NST (CTG) will continue to dominate the science of fetal surveillance. The charm of NST is
Greater specificity
Total non-invasiveness
Golden days of NST (CTG) are round the corner.
Source of Funding
None.
Conflict of Interest
None.
References
- C Y Lee, P C Diloreto, J M Lane. A study of fetalheart rate acceleration patterns. Obstetrics and Gynecology 1975. [Google Scholar]
- . . American Academy of Pediatrics and American College of Obstetricians and Gynaecologists : Guidelines for perinatal care, 7ed 2012. [Google Scholar]