الفهرس 
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Abstract
The yolk sac (YS) is the first extra embryonal structure to become visible within the gestational sac (GS) on ultrasound. It can be identified as early as 5 weeks’gestation, or 3 weeks of embryonal life, and for this reason its presence confirms pregnancy. The YS is the primary source of red blood cells and germinal stem cells to the embryo. The old cognition of the YS having a role in the transfer of nutrients to the embryo during the 3rd–4th week of gestation is now surpassed.
The YS reaches its highest level of functionality at 4–7 embryonic weeks’ gestation.It gradually increases in size in a linear fashion until 10 weeks’ gestation. As its function and vascularity decrease, the YS gradually degenerates and can no longer be identified after 12 weeks’ gestation.
Pregnancy loss is the most common adverse outcome of early pregnancy, affecting 10–20% of clinically recognized pregnancies.
Due to this high incidence, multiple studies have been performed investigating various markers which could possibly identify pregnancies destined to be lost. An enlarged YS, has been associated with this devastating pregnancy outcome, while a misshapen YS has minimal prognostic value.
However, the YS has always been evaluated cross-sectionally with only one ultrasound per patient.In addition, in many studies pregnancy dating was not necessarily accurate. Thus, the nomograms of YS growth reporting cross-sectional data may not be accurate and a precise growth pattern was never established.
In the current study we aimed to evaluate the value of measurement of both size and shape of yolk sac in determining pregnancy outcome.
This study was conducted on 46 pregnant women between 5+0 and 11 weeks of gestation underwent trans-vaginal ultrasound where yolk sac diameter (YSD), gestational sac diameter (GSD) were measured, presence/absence of yolk sac (YS) and shape of the yolk sac were noted. Follow up ultrasound was done to confirm fetal well-being and 12+6 weeks and is the cutoff point of the study or if abortion occurred before that time .
The cases enrolled in this study had a mean age of 28,09±5.61 years and mean BMI was 28.15±1.41 and the main gravidity was 2.37±1.08 and the main parity was 1.24±1.02
In the current study we found that on first visit yolk sac founded among 97.8% of cases and absent in 2.2%, YS shape was normal in 35 cases (76.08%) and was abnormal in 10 cases (23.92%) .
In the current study we showed distribution of the studied patients regarding Yolk sac diameter at different period of follow up. At 6 weeks , mean Yolk sac diameter was 3.5±1.8 mm in aborted cases and 2.2±0.4mm in cases who continued pregnancy , and At 9 weeks, Yolk sac diameter was 4.1 ±1.0 mm in aborted cases and 4.6 ±0.5 mm in cases who continued pregnancy. At 12 weeks the mean yolk sac diameter was 5.3±0.9 mm in aborted cases and it was 5±0.4mm in cases who continued pregnancy .