G Sac seen within the thickened decidua . Eccentric location within endometrium Should abut the endometrial canal ( to differentiate it from decidual cyst ) On TVS -4& half -5 weeks Thresold level – identifies the earliest one can expect to see a sac -4w3d Discriminatory level – identifies when one should always see the sac- 5w 2d .

1. IST TRIMESTER ULTRASOUND

2. EARLY PREGNANCY ULTRASOUND
 GESTATIONAL SAC
 YOLK SAC
 FETAL POLE

3. G SAC
 DOUBLE DECIDUAL SAC SIGN
 INTRADECIDUAL SAC SIGN
 MEAN SAC DIAMETER
 EMPTY G SAC
 PSEUDOGESTATIONAL SAC

4. INTRADECIDUAL SAC SIGN
 G Sac seen within the thickened decidua .
 Eccentric location within endometrium
 Should abut the endometrial canal ( to
differentiate it from decidual cyst )
 On TVS -4& half -5 weeks
 Thresold level – identifies the earliest one can
expect to see a sac -4w3d
 Discriminatory level – identifies when one
should always see the sac- 5w 2d .

6. BETA HCG AND G SAC
 B HCG becomes positive shortly after
implantation long before Gsac visualised by
usg
 1800 mIU/ml –TAS
 > 1000 mIU/ml – TVS

7. DOUBLE DECIDUAL SAC SIGN
 DOUBLE DECIDUA – 1)decidua vera / parietalis
lining the uterine cavity
2) decidua capsularis –lining the G SAC
 These 2 deciduas seen as 2 concentric rings
surrounding the anechoic G sac
 Where the 2 adhere is the decidua basalis –the site
of future placental formation seen as eccentric
echogenic thickening .
 differentiate intrauterine pregnancy from
pseudogestational sac .
 Identified by 5.5 -6 wks of GA ( same time when yolk
sac becomes visible by TVS )

9. MSD

10. YOLK SAC
 Ist structure to seen normally within the G
SAC .
TAS MSD OF 10-15mm
TVS MSD OF 8mm

11.  Y sac should always be visualised at MSD Of
20mm on TAS & 8 mm on TVS .
 CONFIRMS IUP ( double decidual sac sign is
not 100% specific )
 Size – grows at a rate of 0.1mm /mm of MSD
until 15mm of MSD after that growth slows
down to 0.03 mm .
 Upper limit of size between 5-10 wks – 5.6mm
 Number of yolk sac = amniocity of a multifetal
pregnancy

12. EMBRYO / FETUS
 CROWN RUMP LENGTH
 FETAL HEART RATE
 PHSIOLOGIC GUT HERNIATION
 EMBRYONIC RHOMBENCEPHALON

13. CONFIRMING INTRAUTERINE GESTATION
 Double decidual sac sign
 Intradecidual sac sign
 double bleb sign

14. FIRST TRIMESTER VAGINAL BLEEDING
 ECTOPIC PREGNANCY
 FAILED EARLY PREGNANCY
 GESTATIONAL TROPHOBLASTIC
DISEASE
 SUBCHORIONIC HAEMORRHAGE
 DEMISE OF A TWIN
 IMPLANTATION BLEEDING

15. ANEUPLOIDY TESTING
 ANTENATAL SCREENING
 NUCHAL TRANS LUCENCY