Obstetrics Ultrasound Lecture 16 PDF

Radiography & Medical Imaging Science ( Ultrasound Imaging ) Lecture 16 Obstetrics Ultrasound Objectives To understand the basics of screening in the three trimesters of pregnancy. To explore how to assess the ultrasound images in normal fetal conditions during different pregnancy periods For f...

Radiography & Medical Imaging Science ( Ultrasound Imaging ) Lecture 16 Obstetrics Ultrasound Objectives To understand the basics of screening in the three trimesters of pregnancy. To explore how to assess the ultrasound images in normal fetal conditions during different pregnancy periods For fetus biometric purposes Introduction What is Obstetrical Ultrasound Imaging? Imaging an embryo (fetus) within a uterus, as well as the uterus and ovaries. A Doppler ultrasound study may be part of the examination. Trans-abdominal (TA) & Trans-vaginal (TV) probes are used. No special preparation needed. A full bladder is often required for TA scanning. Several examinations are carried out during the 3 trimesters of pregnancy. Establish Establish the presence of a living fetus (check the pt history if she had multiple miscarriage). Estimate Estimate the age of the pregnancy Diagnose Diagnose congenital abnormalities of the fetus Evaluate Evaluate the position of the fetus & placenta Indications Determine Assess Determine the amount of amniotic fluid around the baby Assess fetal growth and well-being Viability scan  First examination done during pregnancy.  This examination is usually carried out vaginally from (6 – 10) weeks of pregnancy + Lab tests to confirm pregnancy.  To determine the number of embryos present and whether the pregnancy is progressing normally inside the uterus.  This scan is useful to assess pain or bleeding in the pregnancy, and miscarriages or ectopic pregnancies.  A visible heartbeat could be detected about of 6 to 7.  Absence of fetal poles (first stage of embryo) or heart beat indicates: missed abortions or non-viability. Viability scan Normal pregnancy at 7 weeks of gestation. Empty sac of an anembryonic pregnancy at 7 weeks. st 1 trimester ( 10 - 14) weeks o Scanning for dating and viability of fetus o Assess chorionicity in multiple pregnancy (The number of membranes that surround babies and separate them in a multiple pregnancy. If there is only 1 membrane, the pregnancy is described as monochorionic; if there are 2, the pregnancy is described as dichorionic, and if there are 3, the pregnancy is trichorionic). o Adnexal assessment of Uterus (Scanning all the area surrounding the uterus. And the uterus in order to check for any fibroids, tumors or any abnormality) o Screening for fetal anomalies Single or multiple pregnancy st 1 trimester's scan include:     Gestational sac Yolk sac Amniotic fluid Circulation (early ultrasound pulsation of the heart)  CRL measurement (Crown to Rump Length)  NT (Nuchal translucency) < 3.5 mm = Normal Gestational sac • The sac which encloses the developing baby and contains amniotic fluid. Yolk sac •Visible about 6 – 12 weeks. •Provides nutrition to embryo until the placenta takes over. Amniotic fluid • The fluid surrounding a fetus within the amnion. 20 ml at 10 weeks 80 - 100 ml at 14 weeks CRL measurement (Crown to Rump Length) • - The measurement of the length of human embryos and fetuses. From the top of the head (crown) to the bottom of the buttocks (rump). 32 mm at 10 weeks 80 mm at 13 weeks 32 mm at 10 weeks 80 mm at 13+6 weeks NT (Nuchal Translucency) • The normal fluid-filled subcutaneous space between the back of the fetal skin and the overlying skin. • To detect chromosomal abnormalities.(Down Syndrome). • Abnormality = value that exceeds of 3.5 mm. ( Measure centre to centre ) 2nd trimester (18 – 22) Weeks Fetal Anatomy scan  It is Important to understand fetal anatomy to be able to scan and interpret US images in the 2nd trimester.  To Exclude any fetal anomalies and growth restriction. 2nd trimester scan include:      Placental location BPD & HC Orbits & Cerebellum Fetal heart AC / stomach  Cord Insertion  Urinary Bladder  FL Femur length together with biparietal diameter, head circumference, and abdominal circumference are computed to produce an estimate of fetal weight.  Spine  Liquor volume assessment Placental location o Placenta is a temporary organ that joins the mother and fetus, transferring oxygen and nutrients from the mother to the fetus and permitting the release of carbon dioxide and waste products from the fetus. Most commonly the placenta is located at the top of the uterus. Placenta location: •anterior (front wall) •posterior (back wall) •side walls (left or right lateral) Biparietal diameter (BPD) and Head Circumference (HC) measurements The Head Circumference (HC) is measured in the trans-thalamic view, which is the same plane as that for the BPD measurement. For the BPD we measure it from the outer to inner border. For the HC we measure the outer edge of the fetal cranium. Orbits Assessments Cerebellum Assessment Transverse diameter of the cerebellum should be measured, as should the size of the cisterna magna Fetal heart ( viability & 4 chambers view ) Reasons for checking heart chambers: • Heart malformation • Heart valves • Reflux of the blood AC ( Abdominal Circumference) / Stomach Stomach bubble The proper plane to take the measurement of AC is the plane that shows the umbilical vein and stomach Cord Insertion • The umbilical cord is the only connection between the mother and the fetus, through which it is possible to transport respiratory gases, and nutrients. • A normal umbilical cord has two arteries and one vein, this is known as a three vessel cord. • one vein that carries food and oxygen from the placenta to your baby and two arteries that carry waste from your baby back to the placenta. Urinary Bladder FL (Femur Length) Spine incomplete closure of the spinal cord Liquor volume assessment (Amniotic fluid volume assessment) Change in volume through gestation:  10 weeks gestation: ~10-20 mL  16 weeks gestation: ~250 mL  33 weeks gestation: ~800 mL  38-39 weeks: plateaus at ~1000 mL  Finally decreases at 40 weeks to ~800 mL Single deepest (Maximum Vertical Pocket) method 3rd trimester ( 28 - 32) weeks Fetal Growth and Well Being Scan  Fetal Growth can only be assessed with an accurate established EDD (expected due date). (Fetal growth appropriate with pregnancy week)  3rd trimester evaluation is primarily to assess appropriate growth and fetal health.  It is important to exclude FGR.  Fetal growth restriction (FGR) is a term used to describe a fetus that is not growing adequately before birth. rd 3 trimester ( 28 - 32) weeks  The scan include some aspects of the 2nd trimester but you can’t see all the anatomical details as the fetus will be fully grown and squeezed. 3rd trimester ( 28 - 32) weeks Fetal Growth Scan 3rd trimester scan include:  Presentation / fetal position  Placental position  HC  AC  FL  Amniotic fluid index (AFI)  Cord Doppler Amniotic fluid index (AFI)  AFI is an estimate of the amniotic fluid volume in a pregnant uterus.  Technique : • The uterus is divided into four imaginary quadrants. • Measurement of the four pockets is in centimeters. • The sum of all the four quadrant measurements is the AFI.  Normal AFI values range from 5 to 25 cm  AFI <5 cm is considered to be oligohydramnios.  AFI >25 cm is considered to be polyhydramnios. Amniotic fluid index (AFI) Late pregnancy Scan (weeks 29 to 40) It is important to monitor the fetus growth. Determine fetus position (head position). Check the placenta location in the uterus before delivery. Decide if the patient will have cesarean (C-section) or normal delivery. Questions??