Obstetric USG — Anomalies and Dating

At what gestational age does the fetal heart rate typically become visible on transvaginal ultrasound?

Which of the following is the earliest sonographic sign of an intrauterine pregnancy on transvaginal ultrasound?

A 28-year-old woman with irregular menstrual cycles presents for dating of pregnancy. Transabdominal ultrasound at 14 weeks (by last menstrual period) shows a single intrauterine gestational sac with a crown-rump length (CRL) of 68 mm. The biometric parameters suggest an age of 16 weeks. There is also a small hypoechoic lesion in the fetal thorax measuring 8 mm with a thin echogenic rim. What is the most appropriate next investigation to characterize this thoracic lesion?

A 32-year-old primigravida presents for routine antenatal ultrasound at 18 weeks gestation. Sonography reveals a single live intrauterine pregnancy with normal biometry for dates. However, the fetal spine demonstrates a midline defect in the lumbosacral region with protrusion of neural tissue and cerebrospinal fluid. The lateral ventricles measure 12 mm. What is the most appropriate next step in management?

A 28-year-old primigravida at 18 weeks of gestation presents for a detailed anatomy scan. The sonographer evaluates the fetal brain, spine, heart, and kidneys. All of the following are recognized second-trimester sonographic findings in normal fetuses EXCEPT: