J. Obstet. Gynaecol. Res. 2016
doi:10.1111/jog.13114
Normogram of umbilical artery Doppler indices in singleton pregnancies in south-western Nigerian women Oluwagbemiga Oluwole Ayoola1, Peter Bulus1, Olabisi Morebisi Loto2 and Bukunmi Michael Idowu1 Departments of 1Radiology, 2Obstetrics and Gynaecology, Obafemi Awolowo University Teaching Hospitals Complex, Ife, Nigeria
Abstract Aim: To determine the Doppler indices of the umbilical arteries in normal singleton pregnancy with a view to generating local reference ranges. Methods: In this prospective, cross-sectional study, 400 pregnant women at 15–39 weeks’ gestational age, with estimated fetal weight within the 10th and 90th percentile, no fetal malformation(s), and without any history of maternal medical disease, were recruited. Umbilical arteries were assessed on ultrasound, with the subjects in the supine position. Resistivity index (RI), pulsatility index (PI) and systolic/diastolic (S/D) ratio were recorded and analyzed. Results: All the umbilical arteries were paired; no single umbilical artery was seen. Mean RI, PI, and S/D ratio declined with gestational age, and decreased from 1.265 to 0.829, from 0.760 to 0.585 and from 4.068 to 2.365, respectively, from 15 to 39 weeks of gestation. With regard to correlation between gestational age and Doppler indices, r = – 0.598 for PI (P < 0.05), 0.437 for RI (P < 0.05), and – 0.538 for S/D ratio (P < 0.05). Decline in the Doppler indices was progressive with gestational age. Conclusion: A normogram of umbilical artery Doppler indices was constructed, which showed that the indices decreased with gestational age. These normative data could serve as reference ranges for evaluation of the umbilical artery circulation in this locality. Key words: Doppler, pulsatility index, resistivity index, systolic/diastolic ratio, umbilical artery.
Introduction The umbilical artery was the first fetal vessel to be evaluated on Doppler sonography1. It is one of the most rigorously evaluated vessels in assessing fetal wellbeing, and has become an invaluable tool for surveillance of high-risk pregnancies.2–4 Knowledge of normal reference ranges can help reduce perinatal mortality significantly through intensive fetal monitoring and appropriately timed delivery.5 Although various investigators have described and established gestational agerelated reference curves,5,6 none has been published for Africa, to the best of authors’ knowledge. The available reference ranges are for Caucasian women, which may not be appropriate for use in this locality, taking into
consideration the significant differences in socioeconomic status, general nutritional status, educational status, and health-care indices between developed and developing countries. To clarify this point, a study on the possible differences in fetomaternal Doppler indices with ethnicity7 is being undertaken. Locally derived reference normal values would facilitate the identification and improved management of fetuses at risk, and help reduce perinatal morbidity and mortality.
Methods This was a prospective, cross-sectional, non-randomized study of 400 consecutively recruited pregnant women
Received: February 15 2016. Accepted: June 19 2016. Correspondence: Dr Oluwagbemiga Oluwole Ayoola, Department of Radiology, Obafemi Awolowo University Teaching Hospital, PMB 5538, Ile-Ife, Osun State, Nigeria. Email:
[email protected]
© 2016 Japan Society of Obstetrics and Gynecology
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with viable singleton pregnancies at the radiology department of the present institution between October 2010 and October 2011. Informed consent was obtained from all subjects and the study was approved by the institutional Ethics and Research Committee. Pregnant women referred for routine prenatal fetal ultrasound, between 15 and 39 weeks’ gestational age, who fulfilled the following criteria were recruited: regular menses and known last menstrual period (LMP) or sonographically determined gestational age during the first trimester; singleton fetus with estimated fetal weight between the 10th and 90th percentiles; no history of maternal medical disease; and no fetal malformation. Non-indigenous subjects were excluded from the study. Each subject recruited into the study was considered only once. Ultrasound was carried out with a Mindray DC-6 with a 3.5–5.0-MHz transducer (Shenzhen Mindray Bio-medical Electronics, Nanshan, Shenzhen, China). To ensure that the subjects were normal, medical history was reviewed, blood pressure and weight were checked from the most recent antenatal records, and routine pregnancy laboratory investigations (urinalysis, full blood count, genotype, urea and electrolytes, retroviral, hepatitis B and syphilis screening) were also reviewed and ensured to be normal. Prenatal fetal ultrasonography was done first for each subject while lying supine with a slight left lateral tilt to prevent orthostatic hypotension from vena cava compression. This was to determine the number of fetuses, estimate gestational age and fetal weight (to ensure the fetuses were not small for gestational age), and exclude fetal malformation(s), as well as placental and amniotic fluid abnormalities. Doppler parameters were optimized in each examination using low wall filter settings
