No abstract

II, after rescanning and use of transvaginal ultrasound (TVUS). The conditions that led to rescanning and TVUS were: BMI greater than 24 in 26% cases, unfavourable fetal position (12.32%), retroverted uterus (12.32%), abdominal scar (10.96%), fibroids (4.11%), and combinations of the above (34.23%). The L-shaped UV confluence was identified transabdominally in 91% in Group I and in 79% in Group II and increased to 98% and 95%, respectively, following re-evaluations. Microscopy represented a useful audit in all FT investigated cases. Conclusions: At the end of the FT, the visualisation of a normal L-shaped UV confluence, that excludes major PVS abnormalities, is achievable in approx. 80%, indifferently to the examiner's experience. The sonographer's experience, pregnant women's BMI, and uterine anomalies as fibroids or retroversion significantly affect the rate of visualisation and necessitates vaginal approach and re-examination. The FT pathology audit of the ultrasound findings can only be performed microscopically, with relatively little resources involved and good results.

Objectives: To assess feasibility of using a basal axial plane to detect lobar holoprosencephaly. Methods: 200 normal fetuses between 17-24 weeks of gestation included along with 7 cases of complete agenesis of corpus callosum, 2 of isolated absent septum pellucidum and 2 of lobar holoprosencephaly. Axial plane passing through the caudal portion of the third ventricle which is seen as a straight echogenic line in the midline between the thalami in continuity with the anterior interhemispheric fissure (figure 1a) obtained for assessing cleavage of the basifrontal region. The appropriateness of the plane ascertained by going more caudally, thereby reaching the circle of Willis and then sliding transducer cranially to reach the basal portion of the third ventricle. Results:The hyperechoic uninterrupted midline linear echo of the basal part of the third ventricle was seen in continuity with the anterior interhemispheric fissure extending into the basal frontal lobes in all fetuses who were normal, with agenesis of corpus callosum (figure 1b) or isolated absent septum pellucidum. It was interrupted anterior to the third ventricle in the basal axial plane (figure 1c) in 2 cases of lobar holoprosencephaly with an intact interhemispheric fissure in the transventricular plane (figure 1d). Conclusions:The basal axial plane of the fetal brain can simplify sifting through the differential diagnosis of absent cavum septum pellucidum by identification of the fusion of basal part of the frontal lobes. The axial section is fairly easy to obtain and the third ventricle is a familiar landmark.

Objectives:To study the incidence of associated anomalies and assess the possibility of spontaneous resolution according to the longitudinal bladder diameter (LBD) in fetuses with megacystis. Methods: This is a retrospective study of prospectively collected data in fetuses diagnosed to have megacystis in the first trimester in a tertiary referral centre in South India. 84 fetuses with megacystis were assessed for presence of associated anomalies, rate of spontaneous resolution and immediate postnatal outcome during the study period from January 2007 till December 2021. All scans were performed by FMF certified operators and data was maintained on Astraia database software. Results: Of the 84 fetuses, 15 (17.8%) fetuses were part of a multiple pregnancy. 34 (40.5%) had a longitudinal bladder diameter (LBD) between 7-15 mm (G1) and 50 (59.5%) had an LBD of equal or more than 16 mm (G2). 2/34 (5.9%) and 3/50 (6%) in G1 and G2 respectively had an aneuploidy and hence terminated. 13/34 (38.2%) and 14/50 (28%) in G1 and G2 respectively had associated anomalies, mainly affecting the skeletal system and cardia. Of the 11 continuing pregnancies, 8 (72.8%) and none in G1 and G2 respectively showed spontaneous resolution before 20 weeks. Conclusions: Megacystis is an easily identifiable anomaly in the first trimester. There is nearly 6% incidence of aneuploidies, irrespective of the LBD. In our study, the incidence of spontaneous resolution in the 7-15 mm group was over 70%. However, none in the more than 16 mm group resolved spontaneously. All fetuses with diagnosis of 1st trimester megacystis must be categorised according to the LBD and offered karyotyping. In the isolated group, when LBD is less than 15 mm, the prognosis appears to be favourable in most fetuses. EP31.06Prenatal diagnosis and outcome of antenatally detected congenital talipes equinovarus deformity: a single centre study from South India