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

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Predictive Value of Yolk Sac in Early Pregnancy by Ultra-Sonography Powered By Docstoc
					Predictive Value of
     Yolk Sac
in Early Pregnancy
by Ultra-Sonography
             Presented by
   Dr. Narayan M.Patel  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-380014 Gujarat state (INDIA)
Phone:- (079) 27682572
E-mail:-narayanpatel1932@yahoo.com
          Yolk sac
1979: - Mantoni & Pederson,
     first visualized yolk sac with
static ultrasound equipment
1980:- Sauerbrel & Croozi adopted
      real time imaging
Primary yolk sac is a microscopic structure
and not seen on ultra sound.
                                    Secondary
                                    yolk sac




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


                               Yolk sac




Early embryo develops along the
outer margin yolk sac as shown by arrow.
The yolk sac is attached to the embryo by
the body stalk and flouts freely in the
extraemryonal coelom, until 10th week.
                                                  Yolk sac

                                                   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 12-14 weeks yolk sac is no longer seen.
 Yolk sac and gestational sac
1) Y.S. may be visible earliest, when mean sac
  diameter of G.S. is 8 mm.
2) 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.
               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
                YOLK SAC

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.
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.
                                               Fetal pole


                                               Yolk sac




Foetal pole and yolk sac may not be seen in the same plane
at sonography, as shown in this slide
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.
The exact functions of the yolk sac are
   largely unknown.
It may play a role in:--
(1) 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.
(2) Haematopoiesis
(3) Formation of primitive gut.
(4) Germ cell formation.
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.
                                             Fotal pole




Yolk sac at L.M.P. 2 months
Yolk sac 6.2 mm. A poor prognosis was forcasted to the
patient.
Big yolk sac measuring   Big yolk sac measuring
                           l
6.5mm                    6.2mm
                           l


       Both cases has poor prognosis.
Large yolk          Fractured yolk sac

 Poor prognosis in both the cases
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
L.M.P. 2 months. Big yolk sac         Large yolk sac of 6.8 mm . Fetal
of 6 mm in diameter. No fetal pole.   pole is seen However prognosis
A case of blighted ovum               in this case will be poor.


Abnormally large yolk sac results from accumulation
of nutrients, not used by the embryo.
              1                               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.
                                   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.
                                    Yolk sac



                                           Yolk sac




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.
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
                                               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
                                         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.
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.
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.
              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.
   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.

				
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