Descriptive study on early antenatal ultrasound scanning

Abstract

INTRODUCTION: Routine ultrasound scan (USS) between 16-22 weeks of gestation renders an opportunity, to provide accurate estimation of gestational age, to diagnose multiple pregnancies, to identify fetal chromosomal and structural abnormalities, to locate the placenta, and to estimate the amniotic fluid volume. In addition, first trimester USS helps in the diagnosis of early pregnancy complications such as missed abortions and hydatidiform moles. OBJECTIVES: To determine the percentage of mothers who were scanned before 24 weeks of gestation and to evaluate its benefits. METHODS: One thousand and two hundred consecutive mothers were recruited to the study. Mothers scanned before 24 weeks of gestation were identified and USS findings were recorded. Expected date of delivery according to the last menstrual period and USS were noted, and these were compared with the actual date of delivery. Mothers with placenta praevia at term were analysed to see the co-relation with USS finding of a low-lying placenta. Mothers who delivered babies with abnormalities were also recorded. Setting: Colombo North Teaching Hospital, Ragama, Results: Only 24.2% of the mothers had an USS before 24 weeks of gestation. Of the 242 mothers, 42 had a discrepancy between the menstrual dates and dates estimated by USS. In 46 mothers dates estimated by USS differed from the actual date of delivery of term babies. There were 26 mothers who had placenta praevia at term (2.6%) out of whom only 12 had an early USS. Low lying placenta was detected in only four mothers and one had no comment about the placenta during early USS. There were no foetal abnormalities detected by USS, but one baby whose mother did not have an early USS was born with a neural tube defect. Among nine intrauterine deaths, four had early USS. Postmortems were done on five of the nine but no abnormalities were detected. There were four mothers with twin pregnancies, all detected by early USS. There were no cases of polyhydramnios, but excessive liquor was noted in six mothers at early USS. CONCLUSIONS: Early ultrasonography is useful to correct dates (17.3% had incorrect dates in this study). The fact that all babies were delivered before the USS date is probably due to smaller babies giving small for dates parameters on USS. Careful localization of the placenta on USS is necessary to improve the accuracy in predicting placenta praevia.