Normal images in early pregnancy as mentioned

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Normal images in early pregnancy As mentioned previously, to be conservative and to practice with the greatest safety, only an intrauterine yolk sac, fetal pole, or intrauterine fetal heartbeat Diagnostic ultrasound 101 First trimester ultrasound
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should be identified as an intrauterine pregnancy on bedside ultrasound scans. The reason for this is that although a gestational sac can be an early marker of a normal gestation, it can also be the result of hormonal stimulation caused by an ectopic pregnancy, known as “pseudogestational sac of ectopic pregnancy” [ 3,13 ]. This finding is seen in up to 10–20% of all ectopic pregnancies [ 13 ]. Therefore, it is not recommended to use this finding as a sign of normal gestation. The “double decidual sign” has also been described as a reliable marker for early intrauterine pregnancy ( Figure 4.10 ). This is a sac with echogenic and hypoechoic rings surrounding it. However, even in the radi- ology and obstetric literature, there is debate as to the accuracy of this finding, and it is not present in all cases. Thus, before the appearance of a yolk sac, an IUP should not be definitively diagnosed by bedside emergency ultrasound. (A) (B) Figure 4.10 Double decidual sign. The hyperechoic layer surrounding the gestational sac can be seen in both ( A ) longitudinal and ( B ) transverse views. However, because there is no yolk sac visualized within the gestational sac, this cannot be definitively called an intrauterine pregnancy. 102 Diagnostic ultrasound First trimester ultrasound
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When first visible, the gestational sac contains no identifiable structures. By the time its diameter reaches 5–8 mm, the yolk sac (“sac within the sac”) should be detectable ( Figure 4.11 ). By the end of the sixth menstrual week, the mean diameter of the gesta- tional sac grows by 1 mm/day, the yolk sac appears, and embryonic cardiac activity may be seen between the yolk sac and the wall of the chorionic sac even before the embryo is measurable. At this point, the tiny embryo is surrounded by a small amniotic membrane. This complex, located between the yolk sac and the chorionic wall, is termed the fetal pole ( Figure 4.12 ). The embryo grows by about 1 mm/day in crown–rump length, and by the end of the seventh menstrual week the embryo measures 5–10 mm (A) (B) Figure 4.11 In ( A ), the double decidual sign is clearly seen. More importantly, a yolk sac is seen in both ( A ) and ( B ). This “sac within the sac” (yolk sac) is the first definitive sign of an intrauterine pregnancy. Diagnostic ultrasound 103 First trimester ultrasound
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( Figures 4.13 and 4.14 ) and should exhibit cardiac motion on both transva- ginal and transabdominal scanning. The gold standard for the diagnosis of a living intrauterine pregnancy is the visualization of embryonic cardiac activity. This may be seen as early as 41–43 menstrual days (6 weeks) or when the mean sac diameter is 12–16 mm.
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