1. Predictive Value of
Yolk Sac
in Early Pregnancy
by Ultra-Sonography

2. Dr. Narayan M.Patel Presented by
M.D,D.G.O.,F.I.C.S
Prof.Emeritus, ob/gyn.muni.medical collage,
Postal address:-
Mahalaxmi institute of medical teaching
3, shantiniketan park, Nr. S. P. Colony
Ahmedabad Gujarat state (INDIA)
Phone:- (079)

3. 1980:- Sauerbrel & Croozi adopted real time imaging
Yolk sac
1979: - Mantoni & Pederson, first visualized yolk sac with static ultrasound equipment
1980:- Sauerbrel & Croozi adopted
real time imaging

4. Primary yolk sac is a microscopic structure
and not seen on ultra sound.

5. What we see on ultra sound is the secondary yolk sac.
Yolk sac is a spherical membrane quite
ecogenic and readily seen at sonography.

6. Early embryo develops along the
Fetal pole
Yolk sac
Early embryo develops along the
outer margin yolk sac as shown by arrow.

7. The yolk sac is attached to the embryo by
the body stalk and flouts freely in the
extraemryonal coelom, until 10th week.

8. By seventh week the yolk sac occupies a space between
Amnion
Foetal pole
By seventh week the yolk sac occupies a space between
the chorion and fetus. At this gestational age, it has an
important prognostic role. At 10th week with increasing growth
of embryo, yolk sac become smaller and smaller and displaced
at periphery. After weeks yolk sac is no longer seen.

9. Yolk sac and gestational sac
Y.S. may be visible earliest, when mean sac diameter of G.S. is 8 mm.
one must see yolk sac when G.S. is 13 mm. or more
3) Y.S. if not seen, when G.S. is more than 20 mm. it means it is a case of blighted ovum.
4) The yolk is a definitive evidence of a true gestational sac.
5) Presence of yolk sac confirms intrauterine pregnancy
6)Presence of yolk sac however does not guarantee a normal out come of pregnancy. .

10. After 7 weeks yolk sac is static, till it
Size of Yolk sac
Weeks of gestation Yolk sac diameter
5 weeks 3 to 6 mm
6 weeks 4 to 5 mm
7 weeks 5 mm. (Embryo seen)
8 weeks 5 mm. (embryo 10mm)
After 7 weeks yolk sac is static, till it
disappear by the end of first trimester.
Normal acceptable size of yolk sac 5.0 .to 5.5mm

11. Yolk Sac Seen at G.S. diameter. By T.V.S. 5 weeks preg. 8 to 10 m.m.
By T.A.S. 6 weeks preg. 20 mm
At transvaginal sonography, yolk sac is seen
one week earlier than trans abdominal sonography.

12. Yolk sac is the first structure to be seen at T.V.S.
even before fetal pole is seen. This patient had L.M.P.
1 month 7 days and yolk sac is seen.

13. Fetal pole
Yolk sac
Foetal pole and yolk sac may not be seen in the same plane
at sonography, as shown in this slide

14. In measuring yolk sac inner to inner diameter is to be measured.
The walls of yolk sac are not to be included in the measurement.
Yolk sac diameter refers to mean inner diameter of yolk sac.
A yolk sac diameter more than 5.5 mm between 5 to 10 weeks of menstrual age, is associated with poor outcome.
A gestational sac with a mean diameter of more than 8 mm without a yolk sac, indicate non-viability.

15. The exact functions of the yolk sac are largely unknown.
It may play a role in:--
Transfer of nutrients to the embryo. It has been shown that the yolk sac is the source of several embryonic proteins, including alpha fetoprotein, transferin, pre albumin, albumin. alpha antitripsin and apolipo proteins.
Haematopoiesis
Formation of primitive gut.
Germ cell formation.

16. An enlarged yolk sac, greater than 6 mm in diameter can be the first sign of an eventful pregnancy failure.
Yolk sac that is
Too small,
Solid,
Too large
Fragmented, or
Irregular,
is associated with poor pregnancy out come.

17. Fotal pole
Yolk sac at L.M.P. 2 months
Yolk sac 6.2 mm. A poor prognosis was forcasted to the
patient.

18. Both cases has poor prognosis.
Big yolk sac measuring
6.5mm
Big yolk sac measuring
6.2mm ll
Both cases has poor prognosis.

19. Poor prognosis in both the cases
Fractured yolk sac
Large yolk
Poor prognosis in both the cases

20. Big yolk sac and no fetal pole.
A case of blighted ovum
Gestational sac is irregular.
Measures 18mm.
No fetal pole or yolk sac seen
Confirms as missed abortion

21. Abnormally large yolk sac results from accumulation
Large yolk sac of 6.8 mm . Fetal pole is seen However prognosis in this case will be poor.
L.M.P. 2 months. Big yolk sac
of 6 mm in diameter. No fetal pole.
A case of blighted ovum
Abnormally large yolk sac results from accumulation
of nutrients, not used by the embryo.

22. 1--This Pt., Mrs. M, had yolk sac of 6.5 mm in early pregnancy. 2 1
1--This Pt., Mrs. M, had yolk sac of 6.5 mm in early pregnancy.
She was told that prognosis likely to be not good.
2-- On further follow up, Mrs. M, at 10 weeks pregnancy
the Yolk sac decreased in size and there is no fetal pole
even at 2 months 8 days preg. Confirmed as blighted ovum.

23. However in this case Yolk sac become regular
Small and irregular yolk
sac at early pregnancy.
However in this case Yolk sac become regular
and of normal size on follow up. So if in doubt, full
cases follow up is mandatory.

24. A case of Bin ovular twins. Yolk sacs are seen in both
gestational sacs. Fetal poles are not seen in this view.
In multiple pregnancy embryonic well beings can
and should be documented at every visit, until the
pregnancy is past first trimester.

25. Both fetal poles are well seen. Yolk sacs not seen in this view
A case of twins pregnancy. L.M.P. 1 month 25 days
Both fetal poles are well seen. Yolk sacs not seen in this view

26. Yolk sac
Yolk sac
A case of Triplets. Three sacs are seen, marked as 1. 2 and 3
Yolk sacs are seen faintly in No 1 and No 3, as shown by arrow

27. Yolk sac
Rhobencephalon
(not to be mistaken
As second Yolk sac)
L.M.P. 1 month 25 days. Yolk sac is seen shown by arrow
In the fetal pole in head, shows a collection of fluid -called
Rhombencephalon. It mimics a second yolk sac. Be careful
not to describe it as second yolk sac.

28. If only one ultra sound is to be performed in a pregnancy, then the 8 week ultrasound provide the most reliable information of eventual out come of pregnancy.
Embryonic period is between 5 to 10 weeks of menstrual age. This period is the most critical phase of prenatal development & most major anomalies are arising in this period.

29. Absence of yolk sac in presence of an embryo is always abnormal, and may follow embryonic demise.
The anatomical and functional details obtained with Trans-vaginal ultrasonography in early pregnancy are very valuable for the care of pregnant woman.

30. Conclusion
Yolk sac of normal size, number & quality is a forerunner of normal pregnancy.
Monitoring of yolk sac has got a definite predictive value in the well being of developing fetus.

31. Recurrent abnormal yolk sac with early abortion is often
Conclusion (Cont.)
Recurrent abnormal yolk sac
with early abortion is often
due to chromosomal
abnormalities.
Regular USG monitoring of yolk
sac is always desirable in
early pregnancy.

32. THANK YOU