Reference ranges Of Uterine Artery Doppler Indices (Pulsatility index and Resistivity index) in pregnant women of Eastern part of Uttar Pradesh INDIA

Anjali Rani (  anjalithesis7@gmail.com ) Institute of Medical Science Madhu Jain Institute of Medical Science RC Shukla Institute of Medical Science Ishan Ishan Institute of Medical Science TB Singh Institute of Medical Science Girish Singh Institute of Medical Science Milad Mohammedzadehasl Institute of Medical Science Ravi Bhushan Institute of Science, Banaras Hindu University Sonal Upadhyay Institute of Science, Banaras Hindu University


Introduction
Doppler plays an important role in early prediction and diagnosis of preeclampsia and intrauterine growth restriction. In 1983 Campbell and his group rst described the association of PE with uterine artery waveform and the appearance of notching together with a high resistance index 1 . They observed that abnormal uterine waveform was associated with more protienuric hypertension. This Doppler is safe, non-invasive and generated the interest to analyze uterine artery till date.
During pregnancy, physiological changes occur at uterine vasculature. It has been shown that as the gestational age increases the resistance to blood ow in uterine vasculature decreases. This change in pregnancy is because of invasion of spiral arterioles by trophoblast 2 Women who failed to modify uterine artery blood ow by 20 weeks of gestation are at greater risk of pre-eclampsia. If there is absence of in lteration of spiral arteries by trophoblast then preeclampsia is very common 3 , 4 . The maternal side of feto-placental circulation is seen by uterine artery parameters. The main parameters of Doppler used to measure these uterine blood ow are uterine artery pulsatility index (PI), and resistivity index (RI).
The present study aims to develop the reference range of uterine artery indices for the North-East Indian population. We normally use parameters of western countries but two populations are ethnically different and hence there is need to develop the reference range for our local population. In this study we made reference range of uterine artery pulsatility index (PI) and resistivity index (RI) at 18 to 22 weeks gestation and at 28 to 34 weeks gestation. Generally, at 18 to 20 weeks pregnant women are advised to opt for level-2 ultrasonography and hence color Doppler of uterine artery can be performed at that time without any di culty. It will be cost effective and save extra visit to hospital. At 28 to 32 weeks gestation time when most of women go for routine screening for color Doppler to rule out IUGR and any other pathology in feto-maternal circulation, measuring pulsatility index (PI) and resistivity index (RI) will be cost effective as well as time saving. This study will provide reference range for our own population of eastern part of India and dependence on western data will be eliminated.

Patient Recruitment
This study was conducted in department of Obstetrics and Gynecology in collaboration with department of Radiology. It is a prospective observational study which includes patient recruited over a period of four years (Jan 2017 to Dec 2020). Ethical clearance was taken from Institutional Ethical Committee (EC/2086). Informed consent was taken from all the patients included in this study. A total of 250 patients have been examined in their 18-22 weeks of pregnancy for their pulsatility and resistivity index.
The same patient were further followed up in their 28-34 week of pregnancy.

Case De nition
Healthy pregnant women in 18-22 weeks of gestation

Inclusion and Exclusion criteria
Normal pregnant women in second trimester of pregnancies were included for the study. Pregnant lady with abnormalities like eclampsia, preeclampsia and others were excluded from the study.

Follow Up
At the start of study there were 250 patients but in 50 patients follow up could not be done at 28 to 32 weeks so these patients were not included.
The whole study is accomplished in two steps: weeks. This was cost effective because patient did not have to spend extra money as there was no funding in this study. This color Doppler was done for early prediction of preeclampsia. The patients who have normal pregnancy and normal color Doppler values were included in the study. The patient having anti-phospholipid syndrome and patient on aspirin therapy were excluded from the study. The patients having fetuses with growth restriction and congenital anomalies are also excluded.
The uterine artery Doppler can be done by two routs. It can be done trans-vaginally as well as by transabdominally. The uterine artery is identi ed on color Doppler. Uterine artery appears to cross the external iliac artery. The angle of insonation was kept less than 30 degree. Doppler gate was put on the entire width of vessel. Then PI and RI of both left and right uterine artery were measured. Uterine artery parameters are not changed by fetal movement and maternal respiration. The angle of insonation should be as close to 0 degree as possible. We calculated 5 th , 25 th , 50 th , 75 th , 90 th and 95 th percentile for pulsatility index and resistivity index of left and right uterine artery. These percentiles were calculated for each group of gestational age i.e rst group from 18 to 22 then in second group of same patients from 28 to 34 weeks of gestation.

Statistical analysis
The data was statistically analyzed using software SPSS v 17.0 for windows.

Results
In this study nomogram tables for left and right uterine artery pulsatility and resistivity index for Indian population were made. There are total 8 tables. Out of which four tables for right uterine artery and four tables for left uterine artery. In each artery pulstility and resistivity index is measured rst starting from 18 weeks to 22 weeks and then from 28 weeks to 34 weeks.
Reference range tables: In Table 1 pulsatility index of left uterine artery starting from 18 weeks to 22 weeks is shown. We can see that as the gestational age increases the value of pulsatility index decreases. But at 21 weeks it has shown some rise but again at 22 weeks it decreases. So any value above 1.19 at 18 weeks and > 1.16 at 22 weeks is abnormal.   As seen in tab 4 the PI of Right uterine artery also decreases from 1.04 to 0.8900. but there is slight increase from 29 week to 30 weeks and then from 32 to 33 weeks. In tab 5 the value of Resistivity Index ranges from 0.6140 to 0.6100. Anything above these values i.e >95th percentile is abnormal. As seen in tab 6 The RI of right uterine artery is 0.6300 at 18 weeks and 0.5800 at 22 weeks.It also shows that as the gestational age advances there is decrease in the value of resistivity index. The RI of of rt uterine artery is 0.5400 at 28 weeks and 0.4900 at 31 weeks. In almost all groups the 95th percentile value is 0.5400 In tab 8 the resistivity index of right uterine artery is 0.5600 at 28 weeks and also at 34 weeks. It has initially shown decrease but later it remain constant.

Discussion
Preeclampsia and eclampsia are major cause of maternal mortality and morbidity 5 . Uterine atrial ow changes during gestational period and can be used as a parameter to diagnose the preeclampsia and eclampsia. Doppler is very important investigation during pregnancy. It is an established method for the monitoring fetal health as well as mother uterine health. Uterine artery Doppler plays an important role in early diagnosis of preeclampsia and IUGR. At 18 to 22 weeks routine anomaly scan is done and at 28 to 34 weeks ultrasound with color Doppler is done to rule out any growth restriction in fetus. Only these gestational ages were taken because it is cost effective and reduces unnecessary visit to hospital. Pulsatility index has been considered as the excellent parameter of Doppler study. The present study has formulated the reference range for uterine artery Doppler PI and RI at gestational age 18 to 22 weeks and also for gestational age 28 to 34 weeks in Indian population. The studies for reference ranges for Indian population are very scanty.
In present study, we have shown that the pulsatility index of left uterine artery decreases as the gestational age increases ( In follow up at 28 to 34 weeks both resistivity index and pulsatility index also decreases or remain constant with increase in the gestational age. From this study we formulated 5th to 95th percentile values for Indian population. Any value above 95th percentile will be abnormal 10  The color Doppler in all patients was not done from department of Radiology. Many color Doppler were done from outside also. So inter observer variation was there. The machine used for doing color Doppler is also different at different centers. It was di cult to convince normal patient to do follow up color Doppler because it was costly and there was no funding in this study. This is small sample size. It need more sample size and multi centre trial for better result and formulation of reference range.

Conclusion
Doppler is very good investigation for diagnosis of preeclampsia and IUGR so that timely management can be done for better outcome. The reference range of uterine artery pulsatility index and resistivity index for our populations are very useful for early prediction and diagnosis in obstetrics.In this study new charts for pulsatility and resistivity index of uterine artery were made at gestational age from 18 to 22 weeks and also for gestational age 28 to 34 weeks. The 95th percentile value may act as a cut off to detect abnormalities.