Intrauterine sonographic assessments of embryonic heart diameter.

Our purpose was to evaluate embryonic heart diameter in early first-trimester pregnancy using intrauterine sonography with a 20 MHz flexible catheter-based high-resolution real-time miniature transducer. A total of 40 women about to undergo therapeutic abortion from 6-9.9 weeks gestational age and one abnormal pregnancy with fetal hydrops at 9 weeks were studied with a specially developed catheter-based high-resolution real-time miniature (2.4 mm outer diameter) ultrasound transducer (20 MHz). A curvilinear relationship was found between the menstrual age and embryonic heart diameter (R2 = 95.7%), and a normal range of embryonic heart diameter for estimating the growth of the embryonic heart during early first-trimester pregnancy was generated. A normogram of menstrual age as predicted by embryonic heart diameter was also established. There was a good curvilinear correlation between embryonic heart diameter and crown-rump length (R2 = 90.1%). The embryonic heart diameter/crown-rump length ratio rapidly decreased from week 6 to week 7, and remained almost constant thereafter. Embryonic heart diameter (5.2 mm) in the case of fetal hydrops at 9 weeks was above the normal range. These results may provide an additional method of estimating gestational age in the early first trimester of pregnancy. In this limited series, a single case of embryonic heart enlargement was demonstrated, suggesting its potential use in the detection of embryonic congestive heart failure.