Ultrasound in obstetrics

Ultrasound in obstetrics
1.Introduction
2.Definiation
3.Equipments use in ultrasound
4.How ultrasound works
5.Indication of obstetric ultrasound
6.Finding in the first trimester scan
7.Mid trimester ultrasound
8.third trimester scanning
9.Thanku

1. Ultrasound in Obstetrics Presented by- Atul Yadav (RN,RM)

2. Introduction:- The development of ultrasound has dramatically altered obstetric management. It forms an important tool to detect congenital fetal anomalies, assess gestation maturity and guide invasive diagnostic and therapeutic obstetric procedures and measures blood flow.

3. Definition: It is a sound wave beyond the audible range of frequency greater than 2MHZ (cycles per second). The SONAR stands for "Sound , Navigations and Ranging“. The clinical applications of ultrasound in obstetrics was introduced and popularized by IanDonald in Glasgow in 1958.

4. Equipments use in ultrasound: 1. Transducer:- Is a device that converts variations in a physical quantity, such as pressure or brightness, into an electrical signal, or vice versa. 2. Video display terminal:- It display the inner structure of body that is received by the recover in the form of signal.

5. Cont… 3. Frequency range:- Ultrasound frequencies in diagnostic radiology  rang-e  from 2 MHz to approximately 15 MHz.

6. How Ultrasound works: Sound emitted at high pitch does travels in a more or less straight line. At a low pitch it spreads out. Sound that is produced at a very high pitch is therefore transmitted in a narrow beam which is produced by a type of reducer. The transducer trans-form electrical energy to sound and back again. When the transducers placed on the body, a sound wave passes into the body and en-counters a structure; a fraction of the sound is reflected back.

7. Cont… The amount of sound from each organ varies according to the t ype of tissues encountered: 1. Strong echo's give bright white dots. For e.g. Bones 2. Weaker echo’s give various shades of grey according to strength. 3 Fluid filled areas cause no refection and give rise to a black image

8. Indications of obstetric ultrasound: It can be divided into fetal , uteroplacental and maternal. 1. Fetal :- a . Diagnosis of pregnancy. b . Assessment of gestational age. c . Diagnosis of multiple pregnancy d. Diagnosis of IUFD. e. Detection of anomaly. F Assessment of growth (IUGR). g. Assessment of wellbeing. h. Diagnosis of presentation. i . Diagnosis of ectopic pregnancy.

9. Cont… 2. Uteroplacental: a. Localization of placenta (placenta previa). b. Diagnosis of abruption placenta. c. Diagnosis of molar pregnancy. d. Diagnosis of uterine malformations. e. Assessment of liquor volume. f. Uterine size either < or > dates. g. Diagnosis of cervical incompetence.

10. Cont… 3. Maternal: a. Pelvic mass diagnosis and follow up. b. As an adjunct to obstetric intervention. c. Amniocentesis. d. Chorion villous sampling. e. Cordocentesis. f. Fetoscopy. g. Intrauterine fetal therapy (transfusion)

11. Findings in the First Trimester Scan: 1. Fetus: Fetus can be generally well visualized satisfactorily after7 complete week of gestation. The scan done should be able to in form the following: a. Regular fetal heart pulsation. b. Measurement of CRL. c. Fetal activity

12. Cont… 2. Amniotic cavity: It measures about 10mm at 5 weeks and 15mmat 6 and 7 weeks of pregnancy. 3. Trophoblastic layer of placenta: The site where the trophoblasts seems to be localizing to form the placenta is important in the first trimester in woman in whom a chorion villus sampling is indicated on medical grounds.

13. Cont… Advantages: 1. Estimation of gestational age in most accurate 4- 5 days, provided the crowm lump length can be measured. 2. Evaluation of any adrenal pathology is easiest at this stage of pregnancy.

14. Cont… Disadvantages: 1. Satisfactory evaluation of the fetal structure is not feasible. 2. Fetal number may show a change on subsequent scanning lateron . 3. Placental location may appear to change as pregnancy progress because of differential growth rates at different parts the uterus.

15. Mid trimester ultrasonography : Findings: 1. Fetal growth: Is calculated on the basis of an accurate gestational age and is expressed in percentiles. Normal fetal weight is between 10th and 90th percentiles. Weight less than 10 percentileis considered as small for gestational age and more than 90thpercentile is large for gestational age.

16. Cont… 2. Fetal heart: Four chamber view of heart and evaluation of out-flow track are done for screening of congenital heart diseases. 3. Fetal gender identification: It is confirmed by detection of testes within the scrotum in the third trimester. 4. Placenta and umbilical cord: It is discoid shape. Placental thickness is 30mm. Placental thickness if more than 45mm at any period is considered abnormal.

17. Third trimester scanning: 1. Amniotic fluid: Decreased: Oligohydramnious is diagnosed when there is no amniotic fluid pocket of 1.0 cm in size in two perpendicular plane b. Excessive: Hydramnious is diagnosed when the largest single pocket is 8.0 cm in two perpendicular planes.

18. Cont… 2. Viability of the fetus: a. Heart pulsation. b. Fetal limb movements. 3. Placenta: a. Location, Fundal, Anterior, Lateral, Posterior, Low lying. b. Abruption, presence of retro placental clot.