19th World Congress on Ultrasound in Obstetrics and Gynecology Poster abstracts in pregnancy. In publications low PP13 levels have been associated with pre-eclampsia, HELLP syndrome and IUGR. Due to the low PP13 levels in the first trimester, the analytical performance of the PP13 assay is critical. For research study purposes it is important to be able to measure PP13 with a high sample throughput and using low sample volumes to save valuable samples. These properties have been improved in the recently developed AutoDELFIA PP13 Research kitf * compared to the manual PP13 ELISA kit * . Method: The non-clinical performance (precision, linearity and analytical limits [LoB, LoD and LoQ]) of recently developed AutoDELFIA PP13 Research was assessed based on EP15, EP- 6 and EP-17 guidelines, respectively. The variation was determined in 24 runs with 72 replicates using two AutoDELFIA systems and two kit lots. The assays were run according to the kit insert using 25 μL sample volume. Results: Mean total variation was 6.6%, the within lot variation was 5.4%, and the between lot variation was 3.8% (5 samples, concentration range 3.8–446 pg/mL). For the sample with lowest PP13 concentration of 3.8 pg/mL, the respective variations were 9.5% (total), 8.5% (with-in-lot) and 4.2% (between-lot). The assay was found to be linear in the range from 0 to 660 pg/mL PP13 (maximal observed difference < 2.2%). LoB was found to be 0.15 pg/mL, and LoD and LoQ at least 3.8 pg/mL. Conclusions: The results show that the AutoDELFIA PP13 Research kit is well suited for automated quantitative measurement of PP13. Furthermore, the non-clinical performance characteristics and usability of the evaluated assay were significantly improved. P19.05 Longitudinal estimation of fetal growth by ultrasound: a new proposal for the assessment of intrauterine growth restriction J. Nien 1 , S. Illanes 1,2 , C. Cabrera 1 , M. Schepeler 1 , H. Figueroa 1,2 , J. Martinez 1 , E. Osorio 1 1 Obstetrics and Gynecology, Clinica Davila, Santiago, Chile; 2 Obstetrics and Gynecology, Universidad de Los Andes, Santiago, Chile The assessment of fetal growth is usually based on classifying the estimated fetal weight (EFW) into a reference curve, which may over or underestimate growth restriction. The main limitation of this technique has been the undeterminable bias of these birthweights as reference for the normal population, since premature birth itself is related to pathological states that may affect the intrauterine growth. We propose a new method based on longitudinal approach to examine the rate of EFW increment along gestation. Methods: A one year period was considered in this study. The inclusion criteria were: 1) more than 3 ultrasound scans; 2) normal pregnancies delivered at term. EFW were calculated using the equation published by Hadlock et al. Ultrasound examinations were performed by experienced physicians (Voluson 730-Pro). Equation analysis was based on linear model, after logarithmic transformation of the gestational age (GA) and EFW. Normal values for the constant (C) and slope (S) with its 99% lowest confidence intervals (LCI) were calculated. Results: 355 patients were included in the study. Linear model curve fit was R2 = 0.98. Normal parameters were: C =-4.147 (SE = 0.066); S = 3.375 (SE = 0.019); LCI = 3.278. The method was tested on a second set of patients for validation: curve parameters were similar to the first set (R2 = 0.98) for those pregnancies within 10 th and 90 th percentiles (C =-3.935, SE = 0.049; S = 3.307, SE = 0.014; LCI99% = 3.278), but different for those < 10th percentile (C =-3.69, SE = 0.145; S = 3.164, SE = 0.044; LCI99% = 3.078). A subgroup of patients within 10 th and 90 th percentiles showed similar growth parameters than those < 10th percentile. * For Research Use Only Conclusion: This method may provide a better way to distinguish patients with intrauterine growth restriction from those constitu- tionally small for gestational age, and could better define fetuses at risk for intrauterine growth restriction regardless of their percentile classification. P19.06 Learning curve of the measurement of fetal biometry by two-dimensional and three-dimensional ultrasonography F. Yang 1 , K. Y. Leung 1 , H. Y. Chan 2 , Y. P. Lee 2 , H. Y. Tang 2 1 Obstetrics & Gynecology, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China; 2 Prenatal Diagnostic and Counseling Department, Tsan Yuk Hospital, Hong Kong, China Objectives: To determine whether there is any difference in the learning curve of the measurement of fetal biometry between 2DUS and 3DUS. Methods: For each fetus, the fetal biometry including biparietal diameter (BPD), head circumference (HC), abdominal circumfer- ence(AC), and femur length (FL) were measured by an inexperienced operator who has commenced full-time hands-on training in ultra- sound for three months using 2D and then 3D ultrasonorgaphy (2DI and 3DI). The fetal biometry was also measured by an experienced operator using 2D ultrasonography (2DE) alone as a control. Each biometry was measured twice by each operator. All images were analyzed by two experienced reviewers blinded to the operator’s identity according to the score-based objective evaluation criteria. Results: Fifty consecutive fetuses were evaluated with gestation age of 17 to 34 weeks. There were no differences in the interobserver, intermethod and intraobserver variabilites for 2DI, 3DI and 2DE between the fetal measurements for first 25 cases and second 25 cases (all ICCs >= 0.99). Compared to the first 25 cases, there was no significant increase in the proportion of fetal biometric measurements beyond 1mm of 2DE in the second 25 cases. There was no significant improvement in the image quality score of fetal biometry except AC in the second 25 cases. An improvement in the score was observed in both 2D (5.1 vs 5.4; P = 0.024), and 3D AC images (5.3 vs 5.6; P = 0.025). It took significantly less time to measure both 2D and 3D fetal biometry in the second 25 cases. The time required was shortened by 37.1%, 37.1%, 23.4% and 35.8% for 2D measurements of BPD, HC, AC and FL respectively. The corresponding figures for 3D measurements were 20.7%, 19.2%, 29.4% and 35.0% respectively. There wee no significant differences in the percentages of time shortened between 2DI and 3DI. Conclusion There is no difference in the learning curve of fetal biometric measurements between 2D and 3D ultrasonography. P19.07 Fetal biometric measurements by two-dimensional and three-dimensional ultrasonography by an inexperienced operator F. Yang 1 , K. Y. Leung 1 , H. Y. Chan 2 , Y. P. Lee 2 , H. Y. Tang 2 1 Obstetrics & Gynecology, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China; 2 Prenatal Diagnostic and Counseling Department, Tsan Yuk Hospital, Hong Kong, China Objectives: To compare the reproducibility, accuracy and the time required for the measurement of fetal biometry using two- dimensional (2D) and three-dimensional (3D) ultrasonography by an inexperienced operator. Methods: For every fetus, the fetal biometry including biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were measured by an inexperienced operator using 2D and then 3D saved volumes. As a control, the fetal biometry was also measured by an experienced operator using 2D 254 Ultrasound in Obstetrics & Gynecology 2009; 34 (Suppl. 1): 177–284