A 37-year-old woman, gravida 2 para 1, at 22 weeks gestation comes to the office for a fetal anatomy ultrasound. The patient has had limited prenatal care this pregnancy but had a normal dating ultrasound in the first trimester. Her first pregnancy resulted in a term vaginal delivery. The patient has had no vaginal bleeding, contractions, or leakage of fluid, and she has been taking a daily prenatal vitamin. Vital signs are normal. Prepregnancy BMI was 22 kg/m², and she has had appropriate weight gain. Fundal height is 27 cm. The fetal ultrasound reveals a dilated fluid-filled stomach and dilated proximal intestinal segment, as seen below. The remainder of the bowel has no intraluminal air or fluid. Amniotic fluid measurement shows: Which of the following additional findings is most likely to be found on this fetal ultrasound?

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11ec25c8_da26_df16_bc81_bddcf304295a_MD0003_00 This fetus has a fluid-filled stomach and proximal duodenum with no distal intestinal air or fluid, consistent with complete bowel obstruction caused by duodenal atresia. Due to the obstruction, duodenal atresia appears on ultrasound as a double bubble sign (ie, a fluid-filled stomach and duodenum). Duodenal atresia impairs fetal swallowing of amniotic fluid and, therefore, may cause polyhydramnios (single deepest pocket of amniotic fluid ≥8 cm), as in this patient. Duodenal atresia is commonly associated with trisomy 21 (Down syndrome) and VACTERL (Vertebral, Anal atresia, Cardiac, Tracheoesophageal fistula, Esophageal atresia, Renal, Limb) association. Because these syndromes involve multiple congenital anomalies, the presence of duodenal atresia requires evaluation for other malformations. This patient at advanced maternal age (age >35) likely has a fetus with Down syndrome, which has a high rate (up to 50%) of associated endocardial cushion defects. Therefore, the most likely additional ultrasound finding in this fetus is a ventricular septal defect. Other fetal ultrasound findings associated with Down syndrome include a thickened nuchal fold, esophageal atresia, and a complete atrioventricular septal defect. (Choice A) A diaphragmatic hernia may be an isolated anomaly or associated with trisomy 18 (Edward syndrome), which can present on fetal ultrasound as rocker-bottom feet or clenched hands with overlapping fingers. rocker-bottom feet clenched hands (Choice B) Holoprosencephaly is associated with trisomy 13 (Patau syndrome), which can cause multiple coexisting midline defects (eg, microcephaly, cleft lip/palate, omphalocele). Holoprosencephaly (Choice C) 45,X (Turner syndrome) is associated with horseshoe kidneys that may become obstructed, causing oligohydramnios (not polyhydramnios). Turner syndrome is associated with cardiac defects (eg, coarctation of the aorta), cystic hygromas, and hydrops fetalis. cystic hygromas (Choice D) Myelomeningocele (ie, spina bifida) is a neural tube defect (NTD) due to folate deficiency, which is unlikely in patients taking a daily prenatal vitamin. NTDs are typically an isolated finding. Myelomeningocele (Choice E) Congenital cytomegalovirus infection can cause periventricular calcifications, hydrops fetalis, and abnormal amniotic fluid volumes on ultrasound; however, it is not associated with duodenal atresia. Educational objective: Duodenal atresia, a congenital anomaly causing complete bowel obstruction, presents on fetal ultrasound as a fluid-filled stomach and duodenum (ie, double bubble sign) with associated polyhydramnios. Because it is commonly seen in Down syndrome and VACTERL (Vertebral, Anal atresia, Cardiac, Tracheoesophageal fistula, Esophageal atresia, Renal, Limb) association, the presence of duodenal atresia requires evaluation for other fetal malformations (eg, ventricular septal defects). References: Associated congenital anomalies among cases with Down syndrome. (http://www.ncbi.nlm.nih.gov/pubmed/26578241) Congenital duodenal obstruction: timing of diagnosis during the newborn period. (http://www.ncbi.nlm.nih.gov/pubmed/19798044)

A 37-Year-Old Woman, Gravida 2 Para 1, at 22 Weeks