P02.07: Factors potentially influencing the accuracy of first trimester anomaly scan

Abstract

Efficacy of 12–14 week scan in the detection of fetal organs in a low risk population and in presence of uterine fibromatosis (UF), previous Caesarean section (CS) and twin pregnancy (TW); we compare the detection rate of anomalies in these groups Examined a low risk population in the 12–14 week scan with transvaginal HF probe(12 Mhz); follow up at 19–22, 32–34 weeks and postnatal for all cases. A defined checklist in early study of fetal anatomy was adopted: butterfly sign; posterior fossa with cerebellum, 4 ventricle and cisterna magna; face with nasal bone chin and upper lip; spine; 4 chamber, interatrial/ventricular septum, long-short axis and 3 vessels, right subclavian artery; stomach, umbilical portal and ductal connection; abdominal wall; bowel; kidneys and bladder with umbilical arteries; upper lower limbs with digits of hands and foot axis. Aneuploidies markers excluded. Study group: uterine fibromatosis anterior/lateral > 25 mm or multiple anterior; transverse Caesarean section; twin dichorial pregnancies. 341 cases with available follow-up at 1 year. Percentage of early identification of fetal organs is shown in table 1. In the control and respectively in the UF, CS,TW group the overall first trimester anomaly detection rate was: 40,4%, 71,0%, 38,4%, 0%; for major anomalies: 48,4%, 75%, 50%, 0%; and for minor anomalies: 25%, 66%, 0%, 0%. Twin pregnancy significantly compromises early fetal organ analysis and anomaly detection especially cardiac, kidney and limbs evaluation. CS not significantly reduces diagnostic capability according to low uterine segment modifications. UF doesn't impair first trimester anomaly scan.