9–12 September 2012, Copenhagen, Denmark Poster abstracts occur as a result of a new dominant mutation. Rare recurrences have been attributed to gonadal mosaicism and rarely, to somatic mutation in a mildly affected parent. Both of these cases occurred in a 6 month period and appear to be the result of gonadal mosaicism. Supporting information can be found in the online version of this abstract. P31.04 Antenatal diagnosis of Fraser syndrome without cryptophthalmos at 18 weeks B. Cetinkaya Demir 1 , N. Bolca 2 1 Obstetrics and Gynecology, Uludag University, Bursa, Turkey; 2 Radiology, Uludag University, Bursa, Turkey Fraser syndrome is a rare congenital autosomal recessive syndrome mainly characterized by cryptophthalmos, syndactyly, laryngeal atresia and urogenital defects. The incidence has been found to be 0.43 per 100,000 live born infants and 11.06 per 100,000 stillbirths. Enlarged hyperechogenic lungs contrasted by oligohydramnios, non- visualization of the kidneys and laryngeal atresia were sonographic markers leading to the prenatal detection of this syndrome. We report a case of Fraser syndrome diagnosed at 18 weeks of gestational age in a women whose previous child died because of bilateral renal agenesis. Abnormal sonographic findings included bilateral renal agenesis, bilateral hyperechogenic lung tissue, everted diaphragm, a small heart because of compression by the obstructed lungs, minimal fetal ascites, syndactyly of the fingers and oligohydramnios. These findings together with those of the previously affected child led to the diagnosis of Fraser syndrome. The parents were consangineous. Family elected to terminate the pregnancy. Autopsy results confirmed the prenatal diagnosis. Prenatal diagnosis of Fraser syndrome is possible. Supporting information can be found in the online version of this abstract. P31.05 Monochorionic diamniotic twins discordant for idiopathic infantile arterial calcification J. L. Byrne 1,2 , A. Kennedy 3,1 , T. Pysher 4 , L. Erickson 4 , P. Woodward 3,1 1 Obstetrics & Gynecology, University of Utah, Salt Lake City, UT, USA; 2 Pediatrics, University of Utah, Salt Lake City, UT, USA; 3 Radioloogy, University of Utah, Salt Lake City, UT, USA; 4 Pathology, University of Utah, Salt Lake City, UT, USA Objectives: To review the prenatal imaging and postmortem findings in a rare case of idiopathic infantile arterial calcification (IIAC). Methods: Prospective identification of a rare case seen in an aca- demic referral center. Results: 25 y.o. G6P4014 referred at 25 wk gestation for suspected monoamniotic twins with a pleural effusion in twin A. Comprehensive ultrasound revealed a monochorionic, diamniotic twin gestation. Twin A had severe polyhydramnios and a massive pericardial effusion. The heart was enlarged and the outflow tracts and descending aorta appeared very echogenic. Head and neck vessels off the aortic arch were also echogenic. Ultimately the patient went into preterm labor at 28 wk and required delivery. Twin A died at 3 hrs of life due to severe hypoxemia and cardiac failure. Autopsy confirmed the prenatal diagnosis of IIAC. Twin B was unaffected. Conclusions: Idiopathic infantile arterial calcification is a very rare, presumed autosomal recessive disorder. It is characterized by diffuse calcification of the internal elastic lamina of muscular arteries with stenosis and progressive myocardial ischemia resulting in refractory heart failure. Prenatal diagnosis is rare, but possible, given the char- acteristic finding of increased echogenicity of large vessels such as the aorta in the fetus, with associated signs of heart failure. Supporting information can be found in the online version of this abstract. P31.06 Fetal renal vein thrombosis and reversible hydrops fetalis M. Small , A. James, S. Ellestad Obstetrics and Gynecology, Duke University Medical Center, Durham, NC, USA A 46yo G6P3114 with previous history of preterm delivery at 26 weeks was admitted to the labor ward at 24 weeks gestation following sonographic findings of an a 3 cm dilated cervix with membranes prolapsing through the internal cervical os. Clinical exam was consistent with these findings. She had a normal midtrimester anatomic survey and declined serum screening or karyotype determination. At 27 weeks a follow up ultrasound demonstrated an enlarged and echogenic right fetal kidney which measuring 4.7 cm in length. Fetal abdominal ascites and unilateral pleural effusion were noted at that time, consistent with hydrops. The inferior vena cava (IVC) demonstrated echogenic borders and appeared to be compressed by the right kidney. The amniotic fluid volume was normal. The hydrops resolved at 28 weeks gestation. At 31 weeks gestation she experienced preterm labor and delivered a male infant weighing 1590 g. The infant’s APGARS were 8/9 at birth. Postnatal imaging demonstrated a right renal vein thrombosis extending to the inferior vena cava (IVC). No anticoagulation was administered, due to the infant’s prematurity and risk for germinal matrix hemorrhage. At 7 months of age, he met all developmental milestones. His subsequent evaluations demonstrated negative thrombophilia screening, resolution of the right renal vein thrombosis, a patent IVC, and normal renal function. This case demonstrates an unusual presentation of reversible fetal hydrops and renal enlargement secondary to renal vein and IVC thrombosis of unknown etiology. Supporting information can be found in the online version of this abstract. P31.07 Fetus with congenital syphilis complicated with congenital knee dislocation C. Chen Obstetrics & Gynecology, Changhua Christian Hospital, Erlin branch, Changhua, Taiwan Congenital syphilis is defined as the spirochete Treponema pallidum which is transmitted from a pregnant woman to her fetus. Infection can cause stillbirth, neonatal death, and a wide spectrum of symptoms and signs. Abnormalities of long bone are a common manifestation of early congenital syphilis. Long bone abnormalities associated with fractures and pain were reported. Here we described a fetus with reactive Treponemal pallidum particle agglutination (TPHA) has congenital dislocation of left knee. A 38 year-old woman received antepartum exam at our department since early pregnancy. Positive rapid plasma reagin (RPR) was detected and syphilis was diagnosed later. Three doses of benzathine penicillin at weekly intervals were given during 2 nd trimester. Maternal TPHA titer decreased 4-fold at subsequent follow-up. Ultrasound screening showed no obvious anomaly except for polyhydramnios. Amniocentesis was performed and showed normal karyotype 46 XX with negative RPR. The female fetus weighing 3320 g with Apgar scores 9 and 10 was delivered via vagina delivery at 39 weeks Ultrasound in Obstetrics & Gynecology 2012; 40 (Suppl. 1): 171–310 299