Keywords:
Obstetrics (Pregnancy / birth / postnatal period), Ultrasound-Spectral Doppler, Ultrasound, Screening, Obstetrics
Authors:
E. G. Okwudire1, O. M. Atalabi2, O. O. Alasia1; 1Port-Harcourt/NG, 2Ibadan/NG
DOI:
10.26044/ecr2019/C-1790
Methods and materials
Study Design: This was a prospective,
cohort study of uterine artery Doppler US parameters in healthy pregnant women conducted between July 2016 to June 2017 at Braithwaite Memorial Specialist Hospital (BMSH),
a tertiary hospital located in Port-Harcourt city,
Rivers state in southern Nigeria.
Study Population: One hundred and seventy (170) apparently healthy women with singleton pregnancies between 18 and 26 weeks gestation (LMP or early ultrasound determined) were recruited by consecutive sampling from the Antenatal Clinic (ANC). Women with co-existing medical conditions (e.g Hypertension,
cardiac disease),
multiple pregnancy,
fetal abnormality and gross obesity precluding trans-abdominal scanning were excluded.
Data Acquisition: Patients were scanned using a GE Logiq P6PRO ultrasound machine equipped with a 2-6MHz curvilinear probe.
After a routine obstetric scan,
the transducer was placed 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.
Pulse wave Doppler was updated and the image frozen when at least 3-5 consecutive good-quality waveforms were obtained.
Measurements of the peak systolic,
end diastolic and mean velocities were taken 1cm distal to the point of apparent cross over with the external iliac vessels.
UtAD Pulsatility Index (PI),
Resistance Index (RI),
and Systolic:Diastolic (S/D) ratios (derived automatically by the machine) were recorded on the datasheet.
Findings were considered abnormal if any of the indices was >95th centile or diastolic notching (Fig. 2) 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.
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 the informed consent form signed.