This document summarizes the key aspects and purposes of ultrasound during each trimester of pregnancy. In the first trimester, transvaginal ultrasound is best for early dating and detection of anomalies from 6-10 weeks. The gestational sac and embryo/fetus become visible around 5-7 weeks. In the second trimester, ultrasound is used to assess fetal growth, anatomy, viability, and placement of the placenta from 14-20 weeks. A detailed anatomic survey is done to check for neural tube defects or other anomalies. Doppler ultrasound of blood flow is also assessed. In the third trimester, ultrasound monitors continued growth and checks for any late anomalies from the third trimester onward.

1. SHARON TREESA ANTONY
FIRST YEAR M.SC NURSING
GOVT.COLLEGE OF NU

2. MODALITIES
 A mode
 B mode
 M mode
 Real time

3. FIRST TRIMESTER

4. Purposes
 Dating: 6 weeks: TVS
 Number
 Viability
 Location
 Anomalies : anencephaly

5.  Gestational sac visible from 5 weeks
 Small embryo visible from 6 weeks
 Fetus : 7 weeks
 fetal pulsation
 CRL
Fetal activity
After 10 weeks :BPD,FERMUR, HUMERUS &
ABDOMEN

6. TRANS VAGINAL SCANNING
Best for earliest dating
Gestational sac visible at 5 weeks
TRANS ABDOMINAL SCANNING
 sac visible at 6 weeks
Fetal pole at 7 weeks
Cardiac activity visible from 7.5 weeks

8. Gestational age up to 12 weeks
 In weeks
CRL- 5mm
 In days
 CRL+ 42 OR
mean sac diameter + 30

9. Ultra sound markers of fetal
anomalies
 Nuchal translucency > 3mm ( trisomy 21, 18,13)
 2 gestational sac
 Absent double decidual sac sign/presence of fluid in
pouch of Douglas
 Snow storm appearance : hydatidiform mole

10. SECOND TRIMESTER

11. Benefits
 Viability
 Dating : head circumference
 Multiple pregnancy& congenital anomalies
 Placenta localisation
 Biophysical scoring
 Fetal biometry
 Adjunct to amniocentesis/ cordocentesis

12. Fetal growth
 Hadlock formula for fetal weight
(1.4787+0.001837(BPD)2+0.0458(AC)+0.158(FL)-0.03343
(AC*FL)

13. Gestational age
 Most accurate : 14- 20 weeks
 HC/ AC /FL/BPD
 Single most sensitive : AC

14. Fetal anatomic survey
 Neural tube defects
Cranial abnormalities
 Obliteration of Cisterna magna
 Banana sign
 Lemon sign
 Absence of calvarium
 More BPD/HC& Ventriculomegaly

15. BANANA SIGN

17.  Spina bifida
 Cleft lip/ palate
 Stomach bubble seen from 20 weeks
 Hydrops fetalis
 Hydatidiform mole
 Fetal heart

18.  Fetal Gender Identification
 Placental thickness
 Distance between placental edge & internal os
 Multiple pregnancy: twin peak or lambda sign
 Placenta accreta
 Placental maturity

19. Umbilical cord
 Insertion ( velamentous, vasaprevia)
 Single umbilical artery

20.  Amniotic fluid index: 5- 24cm

21. Doppler
 Uterine artery
 Umbilical artery
 Umbilical vein
 Middle cerebral artery
 S/D Ratio
Biophysical profile

22. THIRD TRIMESTER

23.  Anomalies : duodenal atresia, achondroplasia,
microcephaly
 Fetal weight estimation
 Growth profile

24. Nurse’s Role
TRANS VAGINAL
 Lithotomy
 Drape
 Condom/ transducer sheath filled with coupling gel
 Lubricate
 Transducer cleaned with disinfectant

25. Trans abdominal
 Full bladder
 Supine
 Drape
 towel roll

26. THANK YOU