P09.05: Evaluation of ossification timing of sacral vertebrae by transabdominal sonography in the second trimester of pregnancy

Abstract

The aim of this research is to determine the timing of sacral vertebrae ossification in order to guide the clinicians to early and reliable diagnosis of sacral region anomalies like as caudal regression syndrome and delayed ossification in some skeletal dysplasia. This cross-sectional study was carried out on 292 normal single pregnancies at gestational ages ranged 14 to 25 weeks. The sacral region was evaluated on a coronal plane, in spine up position. Changing probe orientation between sagittal and coronal planes during continuous viewing could help in confirming the presence of the ossification centre. Then the level of the central and lateral ossification centres was recorded in each gestational age. Ossification occurred in a predictable caudal direction pattern. As evident in the table neural arch ossification centres were visualises later. S1 and body of S2 were visualised in all cases at 15-17 weeks+ 6 days and arch of S2 in all fetuses with 17 weeks of gestational age. Body of S3 was detected in all cases at17 weeks and its arch at 20 weeks. All fetuses at 20 weeks of gestational age show sacral ossification in body and arch of S4. Ossification in S5 firstly was found at 18 weeks and progressively with a higher percentage during the following weeks of the gestational age. The gender of fetuses had no statistically significant impact on ossification timing. These data show that by using recent high resolution ultrasound machines sacral vertebral ossification centres can be identified in earlier gestational age which can help in earlier detection of sacral pathologies.