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| ORIGINAL ARTICLE |
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| Year : 2015 | Volume
: 12
| Issue : 2 | Page : 95-104 |
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Umbilical artery Doppler velocimetry study on prediction of adverse pregnancy outcomes among pregnant women with hypertensive disorders in Kano, Nigeria
Rabiu Ayyuba, Idris Sulaiman Abubakar, Ibrahim Adamu Yakasai
Department of Obstetrics and Gynaecology, Bayero University Kano, Aminu Kano Teaching Hospital, P.M.B. 3011, Kano, Kano State, Nigeria
| Date of Web Publication | 10-Nov-2015 |
Correspondence Address:
Rabiu Ayyuba
Department of Obstetrics and Gynaecology, Bayero University Kano, Aminu Kano Teaching Hospital, P.M.B. 3011, Kano, Kano State
Nigeria
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/0331-8540.169296
Background: Doppler velocimetry studies have been widely used to predict adverse pregnancy outcomes in hypertensive disorders of pregnancies. Objective: To identify the pregnant women with hypertensive disorders for umbilical artery Doppler velocimetry to predict adverse pregnancy outcomes. Methods: This was a prospective study among 264 pregnant women with hypertensive disorders. The umbilical artery Doppler velocimetry study was conducted using 3.5 m Hz convex of the Mindry Digital Ultrasound Imaging System (Model DP-8800Plus; Shenzen Mindray Biomed Electronics, China). Results: A total of 264 pregnant women within the age of 18–40 years with a mean ± standard deviation of 31.33 ± 5.92 were studied. One hundred and twenty-four (29.90%) presented with pregnancy-induced hypertension (PIH), 72 (58.06%) had abnormal resistive indices (RIs) of at least 0.58 of which 4 had diastolic notches. The remaining 52 (41.94%) had normal RIs with no diastolic notch. Twenty (4.80%) presented with preeclampsia, 12 (60.00%) had abnormal RI of which four had diastolic notches. One hundred and twenty (28.90%) women presented with chronic hypertension, 72 (60.00%) had abnormal RI of which 16 had diastolic notches. Abnormal RI was associated with low Apgar scores and early neonatal death among the patients with PIH, low Apgar scores among patients with preeclampsia and low birth weight among chronic hypertensive pregnant women. Conclusion: We found abnormal umbilical artery Doppler velocimetry RI to be associated with adverse pregnancy outcomes. However, diverse nature of the hypertensive disorders and adverse pregnancy outcomes revealed different optimum cut-off points for various hypertensive disorders following ROC analysis. Keywords: Adverse pregnancy outcomes, hypertensive disorders in pregnancy, umbilical artery Doppler velocimetry
How to cite this article:
Ayyuba R, Abubakar IS, Yakasai IA. Umbilical artery Doppler velocimetry study on prediction of adverse pregnancy outcomes among pregnant women with hypertensive disorders in Kano, Nigeria. Niger J Basic Clin Sci 2015;12:95-104 |
How to cite this URL:
Ayyuba R, Abubakar IS, Yakasai IA. Umbilical artery Doppler velocimetry study on prediction of adverse pregnancy outcomes among pregnant women with hypertensive disorders in Kano, Nigeria. Niger J Basic Clin Sci [serial online] 2015 [cited 2021 Dec 2];12:95-104. Available from: https://www.njbcs.net/text.asp?2015/12/2/95/169296 |
| Introduction | |  |
One of the greatest fulfilments in women of childbearing age is pregnancy. However, it is sometimes associated with complications that could result in disability and/or death. Such pregnancies are regarded as high-risk. If these high-risk pregnancies are detected early during the antenatal period, appropriate interventions confer a substantial reduction in adverse pregnancy outcomes to both mother and fetus.
Pregnancies complicated with hypertensive disorders are regarded as high-risk and contribute to increased maternal and perinatal morbidity and mortality. Hypertensive disorders in pregnancy may be classified as pre-existent, induced by the pregnancy or both types occurring.[1] Studies in Nigeria have shown that 5–10% of pregnancies are complicated by hypertensive disorders.[2],[3],[4]
The genesis behind abnormal umbilical artery Doppler spectral waveforms in patients with hypertensive disorders in pregnancy is not unrelated to the significant reduction in maternal utero-placental flow in some of the hypertensive disorders.
Reduction in utero-placental blood flow invariably results in deterioration of umbilical artery waveforms.[5] With time, there is a progression of the degree of abnormalities in the umbilical artery Doppler waveform with eventual development of absent or reversed end-diastolic flow.[6] It has been demonstrated experimentally that occlusion of utero-placental flow rapidly revealed deterioration in umbilical artery Doppler indices.[7]
An association between abnormal fetal blood flow and long-term neuro-developmental impairment has also been demonstrated.[8] Doppler velocimetric measurements have been widely used in prenatal diagnosis for more than two decades.[9] This followed the initial reports of successful recording of blood flow signals from the umbilical artery by Fitzgerald and Drumm.[10] The principle that has long been assumed is that insufficient uterine, placental and fetal circulation can be defined with the use of Doppler velocimetry.[11] Observational studies have clearly revealed an association between abnormal velocimetry waveforms and adverse pregnancy outcome such as intrauterine growth restriction, fetal asphyxia and perinatal mortality.[8],[12]
Antepartum fetal surveillance with Doppler ultrasound of umbilical artery has shown a significant diagnostic efficacy in identifying fetal compromise. Its effectiveness in decreasing perinatal mortality has been demonstrated by randomised clinical trials (level I evidence).[13]
A significant relationship has been found between ischaemic pathologic features of the placenta and abnormal umbilical artery Doppler studies.[14] Umbilical artery Doppler velocimetry is a non-invasive tool that defines the intrauterine environment. The pregnancy outcomes associated with severe abnormal umbilical artery Doppler velocimetry have been revealed in several case series.[15],[16] Total absence of end-diastolic flow and reversed end-diastolic flow in the umbilical artery spectral Doppler waveform trace have been associated with an increased perinatal mortality rate ranging from 28% to 80%.[15],[16],[17],[18],[19] A larger case series from nine European centres concluded that caesarean deliveries for all pregnancies complicated by absent or reversed umbilical artery spectral Doppler end-diastolic flow is indicated if gestational age and predicted neonatal weight can be managed by the local neonatal Intensive Care Unit.[18]
This study was designed to identify the umbilical artery Doppler ultrasound velocimetric parameters adverse to pregnancy outcome among antenatal women with hypertensive disorders in pregnancy at the Aminu Kano Teaching Hospital (AKTH), Nigeria.
| Materials and Methods | | |
The study was prospective and conducted at AKTH, which is a Tertiary Health Institution in Kano State, situated in the North-Western Geo-Political Zone of Nigeria. The study population comprised all pregnant women with hypertensive disorders in pregnancy that presented for antenatal booking at 20–24 weeks of gestation. The recruitment was by simple sampling method technique. Women with multiple gestations, fetal congenital anomalies and hydrops fetalis diagnosed by ultrasound, and those who were lost to follow-up till delivery were excluded from the study.
Pregnant women with hypertensive disorders who declined consent for the study and those that chose 'no' following balloting were also excluded.
Informed consents were obtained from all pregnant women participating in the study with respect to responding to the questionnaire and Doppler velocimetry of the umbilical artery. The recruitment was by balloting among the selected women with hypertensive disorders.
Sociodemographic factors of the clients, past obstetric history, medical and surgical history and the history of the current pregnancy were asked and recorded. They were then sent to radiology unit for Doppler velocimetry of the umbilical artery.
Authors of this work performed the Doppler ultrasound examination procedures at the radiology unit, each study participant was asked to lie in a supine position on the ultrasound examination couch. Doppler velocimetry of the umbilical artery was conducted using 3.5 m Hz convex transducer of the Mindry Digital Ultrasound Imaging System (Model DP-8800Plus; Shenzen Mindray Biomed Electronics, China) following application of water soluble coupling gel over the lower abdomen.
The umbilical artery was identified by placing the transducer over the lower abdomen and by randomly directing it towards the uterine cavity to identify the umbilical cord at the placental end using amniotic fluid acoustic window and Doppler sample volume applied over it.
The angle between the ultrasound beam and direction of the blood flow was adjusted to ≤60°.
Spectral waveforms were examined by placing the pulsed Doppler range gate within the vessel. The Doppler scale was adjusted such that the velocity measurement was done without aliasing. Recordings were accepted for analysis only after a clear, steady state was obtained for at least five consecutive pulsatile arterial waveforms. No waveforms were recorded during periods of fetal breathing, body movements or cardiac arrhythmias.
The resistance index (RI) of each umbilical artery was calculated using the formula:
RI = S − D/S
Where, S = systolic velocity, D = diastolic velocity.
The RI was considered abnormal if >0.57. This value was in accordance with the RI considered abnormal in other published works.[20],[21],[22],[23],[24] At this time, the presence of an early diastolic notch was also observed for and considered abnormal when present. The women were then divided into two groups: Those with abnormal umbilical artery Doppler velocimetry (Group A) and those with normal velocimetry (Group B).
Other routine obstetric ultrasound parameters were also recorded to determine the fetal weight, gestational age, the state of the amniotic fluid, placental localisation among others.
They were followed up throughout pregnancy, delivery and early puerperium. Data on gestational age at delivery, Apgar scores at delivery, birth weight, intrauterine fetal death and early neonatal death (ENND) were retrieved among the two groups.
In this study, pre-eclampsia was defined as a blood pressure of ≥140/90 mmHg (systolic blood pressure of 140 or higher and diastolic blood pressure of 90 or higher) during the second half of pregnancy with presence of ≥300 mg protein in 24-h urine or ≥1+ albumin in a random urine sample.[25] Pregnancy-induced hypertension (PIH) was defined as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg in a previously normotensive pregnant woman who was ≥20 weeks of gestation and had no proteinuria or new signs of end-organ dysfunction.[26] Chronic hypertension (CHTN) was defined as systolic pressure ≥140 mmHg and/or diastolic pressure ≥90 mmHg that antedated pregnancy or was present before the 20th week of gestation on at least two occasions or persisted longer than 12 weeks postpartum.[27] Low birth weight (LBW) was defined as a neonatal birth weight lower than 2500 g and preterm labour was defined as delivery before 37 completed weeks of gestational age.
Data were entered into a personal computer and analysed using SPSS version 17 computer software (SPSS Inc. SPSS Statistics for Windows, Chicago). χ2-test was used for categorical data. Where criteria for applying χ2-test were not met, Fishers' Exact Test was used and the P < 0.05 were considered to be statistically significant. Combination of receiver operating characteristic (ROC) curves' graphs under each group of high-risk pregnancies were integrated with Stata, Version 11 (Stata Corp, College Station, Texas), Statistical Software.
The predictive power of umbilical artery Doppler velocimetry for adverse pregnancy (fetal/neonatal) outcomes was expressed by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and relative risk (RR) with 95% confidence interval (CI). A graph of sensitivity against 1 – specificity, also called a ROC curve was used. Approval for the study was obtained from the ethical committee of AKTH.
| Results | | |
During the study period (August, 2013 to June, 2014), a total of 264 consenting high-risk pregnant women at the gestational age of 20–24 weeks were recruited, studied and analysed. One hundred and twenty-four (46.97%) pregnant women presented with PIH, 20 (7.57%) with pre-eclampsia and 120 (45.46%) had CHTN.
The age range of the respondents was 18–40 years with a mean ± standard deviation of 31.33 ± 5.92. The median age was 31.5 years.
Good spectral Doppler tracings were obtained for both abnormal (with and without early diastolic notch) and absent end diastolic flow [Figure 1], [Figure 2], [Figure 3]. | Figure 1: Spectral Doppler tracings depicting high resistive indices of 0.73 in the umbilical artery
Click here to view |
 | Figure 2: Spectral Doppler tracings depicting diastolic notches in the umbilical artery
Click here to view |
 | Figure 3: Spectral Doppler tracings showing absent end-diastolic flow in the umbilical artery
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| Doppler Velocimetry of High-Risk Pregnant Women with Hypertensive Disorders | | |
[Table 1] depicts high-risk pregnancies with normal (Group B) and abnormal (Group A) Doppler velocimetries. One hundred and twenty-four (29.90%) presented with PIH. Seventy-two (58.06%) had abnormal resistive indices (RI) of at least 0.58 (Group A) of which four had diastolic notches. The remaining 52 (41.94%) had normal RIs with no diastolic notch (Group B). | Table 1: High-risk pregnancies with normal and abnormal Doppler velocimetry
Click here to view |
Twenty (4.80%) presented with pre-eclampsia. Twelve of them (60.00%) had abnormal RI of which four had diastolic notches.
One hundred and twenty (28.90%) women presented with CHTN. Seventy-two of them (60.00%) had abnormal RI of which 16 had diastolic notches. The rest had normal velocimetries.
| Diagnostic Indices Of Doppler Velocimetry In Pregnancy Induced Hypertension | | |
[Table 2] below shows the diagnostic indices of Doppler velocimetry in high-risk pregnant women with PIH for prediction of adverse pregnancy outcomes. | Table 2: Diagnostic indices in patients with PIH for prediction of adverse pregnancy outcomes
Click here to view |
At abnormal RIs of at least 0.58, the sensitivity, specificity, likelihood ratio, PPV, NPV and RR were 50.00%, 41.38%, 0.85, 5.56%, 92.31% and 0.72, respectively for prediction of preterm birth. There was no statistically significant difference between PIH patients with normal and abnormal RIs for the occurrence of preterm birth (P = 0.719).
At abnormal RI of ≥0.58, the sensitivity, specificity, likelihood ratio, PPV, NPV and RR were 0.00%, 40.00%, 0.00, 0.00%, 92.31% and 0.00, respectively for prediction of low Apgar scores (Apgar scores of <7 at the 5th min). There was statistically significant difference in Apgar scores between babies of mothers (PIH) with normal and abnormal RI (P = 0.029).
Presence of high RI of ≥0.58 among women with PIH has sensitivity, specificity, likelihood ratio, PPV, NPV and RR of 66.67%, 42.86%, 1.17, 11.11%, 92.31% and 1.44, respectively for prediction of LBW. There was no statistically significant difference between those with normal and abnormal RI (Group B and Group A) with regards to their babies' birth weight (P = 0.760).
Presence of high RI of ≥0.58 among women with PIH has a sensitivity, specificity, likelihood ratio, PPV, NPV and RR of 0.00%, 40.00%, 0.00, 0.00%, 92.31% and 0.00, respectively for prediction of ENND. There was statistically significant difference between high-risk pregnant women (PIH) with normal and abnormal RI for prediction of ENND (P = 0.029).
[Figure 4] below depicts the combined ROC curve' graphs for PIH to predict adverse pregnancy outcomes. The optimal cut-off point for predicting preterm birth was 0.715 with a sensitivity and specificity of 50.00% and 89.70%, respectively (area under the curve [AUC] =0.612, P = 0.290, 95%CI = 0.407–0.818). | Figure 4: Combined receiver operating characteristic graphs for pregnancy induced hypertension
Click here to view |
The optimal cut-off point for predicting low Apgar scores and ENND were both 0.550 with a sensitivity and specificity of 100.00% and 30.00%, respectively (AUC = 0.317, P = 0.213, 95%CI = 0.234–0.400).
The optimal cut-off point for predicting LBW was 0.665 with a sensitivity and specificity of 66.70% and 67.90%, respectively (AUC = 0.637, P = 0.120, 95%CI = 0.494–0.780).
[Table 3] below depicts the diagnostic indices in patients with pre-eclampsia for prediction of adverse pregnancy outcomes. Presence of high RI of ≥ 0.58 in patients with pre-eclampsia has sensitivity, specificity, likelihood ratio, PPV, NPV and RR of 66.67%, 50.00%, 1.33, 50.00%, 66.70% and 1.33, respectively for prediction of preterm birth. There was no statistically significant difference between the two groups (P = 0.648). | Table 3: Diagnostic indices in patients with pre-eclampsia for prediction of adverse pregnancy outcomes
Click here to view |
Similarly, presence of high RI of at least 0.58 in the same group of patients with pre-eclampsia has sensitivity, specificity, likelihood ratio, PPV and NPV of 100.00%, 50.00%, 2.00, 33.33% and 100.00%, respectively for prediction of low Apgar scores. There was statistically significant difference between pre-eclamptic patients with normal and high RI for prediction of low Apgar scores (P = 0117).
Occurrence of high RI of ≥ 0.58 in patients with pre-eclampsia has sensitivity, specificity, likelihood ratio, PPV, NPV and RR of 66.70%, 50.00%, 1.33, 66.70%, 50.00% and 1.33, respectively for prediction of LBW. There was no statistically significant difference of birth weight between the two groups (P = 0.648).
[Figure 5] below shows the combined ROC curves' graphs for pre-eclampsia. The optimal cut-off point for predicting preterm birth and LBW by trade-off were both 0.650 with a sensitivity and specificity of 66.70% and 100.00%, respectively (AUC = 0.667, P = 0.217, 95%CI = 0.400–0.933. The optimal cut-off point for predicting low Apgar scores was 0.715. Both sensitivity and specificity were 100.00% (AUC = 1.00, P = 0.002, 95%CI = 1.000–1.000).
| Diagnostic indices of doppler velocimetry in chronic hypertension | | |
[Table 4] below reveals the diagnostic indices of Doppler velocimetry of patients with CHTN for prediction of adverse pregnancy outcomes. Presence of high RI of ≥ 0.58 has a sensitivity, specificity, likelihood ratio, PPV, NPV and RR of 66.67%, 41.67%, 1.71, 22.22%, 83.30% and 1.33, respectively for prediction of preterm birth. There was no statistically significant difference between the two groups (χ2 = 0.556, P = 0.456). | Table 4: Diagnostic indices in patients with chronic hypertension for prediction of adverse pregnancy outcomes
Click here to view |
Presence of high RI of ≥ 0.58 has a sensitivity, specificity, likelihood ratio, PPV, NPV and RR of 75.00%, 42.31%, 1.30, 16.67%, 91.67% and 2.00, respectively for prediction of low Apgar scores. There was no statistically significant difference between the two groups (P = 0.274).
At high RI of ≥ 0.58, the sensitivity, specificity, likelihood ratio, PPV and NPV were 100.00%, 41.38%, 1.71, 5.60% and 100.00%, respectively for prediction of intra-uterine feta death (IUFD). There was no statistically significant difference between the two groups (P = 0.149).
Presence of high RI of ≥ 0.58 has a sensitivity, specificity, likelihood ratio, PPV, NPV and RR of 85.71%, 47.83%, 1.64, 33.33%, 91.67% and 4.00, respectively for prediction of LBW. There was statistically significant difference between the two groups (P = 0.002).
The presence of high RI of ≥ 0.58 has a sensitivity, specificity, likelihood ratio, PPV and NPV of 100.00%, 41.38%, 1.71, 5.88% and 100.00%, respectively for prediction of ENND. There was no statistically significant difference of ENND between group B and A (P = 0.149).
[Figure 6] reveals the combined ROC curves' graphs for CHTN to predict the presence of adverse pregnancy outcomes. The optimal cut-off point for predicting preterm birth was 0.785 with a sensitivity and specificity of 66.70% and 87.50%, respectively (AUC = 0.618, P = 0.074, 95%CI = 0.450 – 0.786). | Figure 6: Receiver operating characteristic graph for chronic hypertension
Click here to view |
The optimal cut-off point for predicting low Apgar scores was 0.825 with a sensitivity and specificity of 50.00% and 84.60%, respectively (AUC = 0.553, P = 0.497, 95%CI = 0.377–0.729). The optimal cut-off point for predicting IUFD was also 0.825 with a sensitivity and specificity of 100.00% and 82.80%, respectively (AUC = 0.295, P = 0.026, 95%CI = 0.759–0.896).
The optimal cut-off point for predicting LBW was 0.645 with a sensitivity and specificity of 71.40% and 78.30%, respectively (AUC = 0.705, P = 0.001, 95%CI = 0.582 = 0.825). The optimal cut-off point for predicting ENND was 1.315 with a sensitivity and specificity of 100.00% and 96.60%, respectively (AUC = 0.966, P = 0.002, 95%CI = 0.932 = 0.999). The summary for ROC findings of all the high risk pregnancies analyzed in this study were show pregnancies analyzed in this study were shown on [Table 5].
| Discussion | | |
In this study, 124 (29.90%) women presented with PIH. Seventy-two (58.06%) had abnormal RIs of at least 0.58. This showed that at abnormal RIs of at least 0.58 in patients with PIH, the sensitivity for prediction of preterm birth was just 50.00% with low specificity (41.38%), likelihood ratio (0.85) PPV (5.56%), RR (0.72), but the NPV was high (92.31%). Here, low likelihood ratio and RR indicates the presence of high RI is not associated with preterm birth. There was no statistically significant difference of preterm birth between PIH patients with normal and high RIs (P > 0.05). In addition, the RI index was a poor predictor of low Apgar score despite having high NPV (92.31%, P ≤ 0.05).
High RI index was associated with high sensitivity (66.67%) and NPV (92.31%) for prediction of LBW. This shows that majority of those tested negative did not have babies with LBW; likewise, the majority of those with PIH, who had high RI also had babies with LBW. The likelihood ratio and RR were >1, indicating that pregnant women with PIH and high RI delivered more babies with LBW. These findings were, however, not statistically significant (P > 0.05). There was statistically significant difference in ENND between those with the high and normal RIs (P < 0.05).
Although previous studies [20],[21],[22],[23],[24] showed that the RI index of at least 0.58 was associated with adverse pregnancy outcomes, following ROC curves' analysis, the RI of at least 0.715, 0.550, 0.550 and 0.0665 were associated with preterm birth, low Apgar scores, ENND and LBW respectively. This was more realistic especially with preterm birth (AUC = 0.612, 95% CI = 0.407–0.818) and LBW (AUC = 0.637, 95% CI = 0.494–0.780) but further studies with a larger sample size is needed to support these findings.
Arduini et al.[20] examined pregnant women with hypertensive disorders in pregnancy. They measured impedance to flow in the arcuate arteries at 18–20 weeks of gestation. In their evaluation, the abnormal result was defined as RI of at least 0.57. However, Zimmermann et al.[28] reported RI of more than 0.68 as an abnormal result in pregnant women with hypertensive disorders at 21–24 weeks of gestation. Following ROC analysis in our patients with PIH, the cut-off point of abnormal umbilical artery RI index for predicting adverse pregnancy outcomes was 0.715. Taslimi et al.[29] reported similar findings of abnormal umbilical artery RI index.
Sixty percent of the pre-eclamptic patients in this study had high RIs of at least 0.58. This was similar to the findings of Myatt et al.[30] who reported high RI among pre-eclamptic patients when compared with non-pre-eclamptic patients.
Pre-eclamptic patients with high RI of ≥ 0.58, the sensitivity for predicting preterm birth was high (66.67%). The likelihood ratio and RR were all > 1, indicating that the preterm birth rate was higher among those with high RI. The specificity was just 50.00%. Following ROC curves' analysis, the optimum cut-off point was 0.650 with a sensitivity and specificity of 66.70% and 100.00%, respectively. The sensitivity and specificity are in a trade-off with each other and as one increases the other decreases.[31] A cut-off point that will give high sensitivity but lower specificity plays a pivotal role in preventing preterm birth. On the other hand, a cut-off point of RI that will give high specificity is recommended when a false positive result can pose a great danger to the patients,[32] which is the occurrence of adverse pregnancy outcomes. The PPV and NPV were 50.00% and 66.70%, respectively. The sensitivity and specificity are useful mainly when we decide to request for a screening test but when the tests have been done, and the results are ready, PPV and NPV replace specificity and sensitivity.[31],[32]
In predicting low Apgar scores among pre-eclamptic patients, there was statistically significant difference between those with normal and high RIs (P < 0.05). The ROC analysis also showed that the optimal cut-off point of 0.715 for predicting low Apgar scores has the highest sensitivity and specificity (both 100.00%). The AUC was perfect (1.00) and also significant (P < 0.05).
Pregnant women with CHTN had high RI (60.00%). This is comparable to the 55.00% of abnormal Doppler velocimetry among pregnant women with CHTN reported by Gupta et al.[33] in India. The adverse outcomes of LBW were also statistically significant among pregnant women with high RI and CHTN (P < 0.05). There was no statistically significant difference in the prediction of low Apgar scores, preterm birth, IUFD and ENND (P > 0.05). When the data were subjected to ROC analysis, LBW, and ENND have AUC of 0.705 and 0.966 indicating better cut-off points of 0.645 and 1.315, respectively.
| Conclusion | | |
The study confirmed the high prevalence of abnormal umbilical artery RI among high-risk pregnant women with hypertensive disorders at 20–24 weeks of gestation in AKTH.
High umbilical artery RI ± diastolic notch among the high-risk pregnant women was also associated with adverse pregnancy outcomes in some of the high-risk pregnancies.
Although, umbilical artery Doppler velocimetry RI of at least 0.58 has been associated with adverse pregnancy outcomes at 20–24 weeks of gestation in most pregnant women with hypertensive disorders, diverse nature of these high-risk pregnancies and adverse pregnancy outcomes revealed different optimum cut-off points for various hypertensive disorders following ROC analysis.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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