CS distance but not CM level is reproducible. CS distance is significantly correlated with both FL and GA. CS distance could be useful in the assessment of prenatal skin-covered spinal dysraphism.

Objective: To assess the ability to identify the conus medullaris (CM) and measure the conus-sacrum distance (CS distance) on a routine scan and the relationship with maternal and fetal factors. Methods: This was a prospective study. The assessment of the CM and the CS distance and the influence of the body mass index (BMI), gestational age (GA) and fetal position were analyzed. The correlation between the femur length (FL) and the GA with the CS distance was evaluated. Results: A total of 696 fetuses were analyzed. The CM could be visualized in 82.3% of the cases, and the CS distance could be analyzed in 81.2% of the cases. The CM assessment was statistically associated with BMI and fetal position but not with GA. The CS distance assessment was statistically associated with BMI and GA but not with fetal position. We determined a significant association between the FL/CS distance and between the GA/CS distance. Conclusions: Assessment of the CM is possible on most routine scans. The CS distance could be introduced to routine scans for the assessment of prenatal skin-covered spinal dysraphism. High BMI, advanced GA and breech presentation could be potential factors limiting the feasibility of evaluating the CM.

Factors affecting the quality of the volume for advanced neurosonography are gestational age, fetal head position, transvaginal acquisition in sagittal volumes, the acquiring operator and the subjective quality of the volume. © 2016 John Wiley & Sons, Ltd.

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Objectives: Evaluation of microstructure is critical to understanding tissue dysfunction like cervical insufficiency. Collagen is primarily responsible for cervical strength. In animals, collagen disorganizes long before labor. Lack of noninvasive technology sophisticated enough to detect microstructural changes has compromised evaluation in pregnant women. We used quantitative ultrasound methods developed in our lab to detect changes. Methods: Hysterectomy specimens (n = 5) were scanned with 2 linear array transducers (Siemens Antares). Radiofrequency (RF) echo data were acquired (plane parallel to endocervical canal). The angle between the acoustic beam and tissue was used to assess anisotropic acoustic propagation by electronic control of transmit/receive angles from −14 to +14 • . A region of interest (ROI) was selected (locations varied to assure result consistency) and the power spectrum of the RF signals computed for each angle. Results: The power spectra (frequency content) of the backscattered RF signals was different for normal incidence (beams perpendicular to tissue) than those steered +/−14 • regardless of ROI position. With spectra normalized across frequencies, there was no attenuation effect (ie findings are not noise or artifact). Incident v steered beam differences are too large to be diffraction (P < 0.01) and suggest the effective scatterer size (diameter of the interrogated component) is less than 40 µ. Conclusions: This novel approach identifies a component that is aligned (anisotropic) and too small to be muscle. Thus it is likely collagen. Our data suggest it is reliably assessable. Ongoing studies will definitively identify, then quantify and track it in pregnancy; if the cervix behaves as predicted, it will convert from an aligned to a random (isotropic) scattering well before labor. Detecting early structural changes prior to gross changes (such as cervical shortening) may give rise to earlier, more specific interventions for cervical insufficiency. OP16: TWINSOP16.01 First-trimester sonographic screening for aneuploidy in multiple pregnancies W. Sepulveda, A. E. Wong, A. Casasbuenas Fetal Medicine Center, Clinica Las Condes, Santiago, ChileObjectives: To review our experience with first-trimester screening of chromosomal abnormalities in multiple pregnancies using nuchal translucency thickness measurement and nasal bone assessment. Methods: Cases of multiple pregnancy presenting for first-trimester sonographic evaluation and with viable fetuses measuring between 45 to 84 mm were prospectively recruited for this study. Crownrump lengths, nuchal translucency thickness measurements, the presence or absence of the nasal bone, and chorionicity were determined and the information collected in a dedicated database. Results: There were 206 twin pregnancies, eight sets of triplets, and 1 set of quadruplets, for a total of 440 fetuses screened. Information on perinatal outcome was available in all cases. The nuchal translucency was measured in all cases and was found to be greater than the 95 t...