Keywords:
Obstetrics (Pregnancy / birth / postnatal period), Arteries / Aorta, Ultrasound-Spectral Doppler, Screening, Obstetrics
Authors:
E. G. Okwudire1, O. M. Atalabi2, O. O. Alasia1; 1Port-Harcourt/NG, 2Ibadan/NG
DOI:
10.26044/ecr2019/C-1793
Methods and materials
Study Design: This was a prospective study of uterine artery Doppler US parameters in healthy pregnant women.
The data was collected over 12 months,
between July 2016 to June 2017.
Study Site: This study was conducted at Braithwaite Memorial Specialist Hospital (BMSH),
a tertiary hospital located in Port-Harcourt city,
the capital of Rivers state in southern Nigeria. The BMSH provides care to over 1.9 million inhabitant of the city and its outskirts.
Study Population: included one hundred and seventy (170) apparently healthy women with singleton pregnancies between 18 and 26 weeks gestation (LMP or 1st trimester ultrasound determined) recruited by consecutive sampling from the Antenatal Clinic (ANC). Women with co-existing medical conditions/history of medical complications (e.g Hypertension,
cardiac disease),
multiple pregnancy,
fetal abnormality and gross obesity precluding trans abdominal scanning were excluded.
Data Acquisition: after obtaining signed informed consent,
patients were scanned using a GE Logiq P6PRO ultrasound machine equipped with a 2-6MHz curvilinear probe.
A routine obstetric scan was done,
then the transducer was placed obliquely in the lower paracervical area and angled medially till the uterine artery was visualized as it crossed the external iliac artery and vein (Fig. 1),
having originated from the internal iliac artery.
The sample volume was set to cover two-third (2/3) of the diameter of the uterine artery,
and angle of insonation was maintained at 0°.
Gain,
PRF and wall filter were adjusted to obtain clear spectral waveforms with minimal background noise.
Pulse wave Doppler was updated and the image frozen when at least 3 consecutive good-quality waveforms were obtained and measurements of the peak systolic,
end diastolic and Time-averaged mean velocities taken 1cm distal to the point of apparent cross over with the external iliac vessels before any branching of the uterine arteries occurred.
Placental locations were recorded as lateral or central and UtAD Pulsatility Index (PI),
Resistance Index (RI),
and Systolic:Diastolic (S/D) ratios (derived automatically by the machine) were entered in the datasheet.
Findings were considered abnormal if any of the indices was >95th centile or diastolic notching present. The women were followed-up till delivery and pregnancy outcomes were obtained from ANC records.
Data Analysis: Data was analyzed using statistical package for social sciences (SPSS) version 21. Comparison of means was done using the Student’s t-test while categorical variables were analyzed using X2.
Sensitivity,
specificity,
positive predictive value (PPV),
negative predictive value (NPV) and likelihood ratios (LR) were calculated from contingency tables.
The screening performance of the indices was compared by constructing ROCs.
P-values of 5% (P<0.05) were considered significant.
Ethical Considerations: Ethical Approval was obtained prior to commencement of the study.
Participants were recruited only after the purpose of the study was explained to them and obtaining written informed consent.