OB Introduction

Course Overview

Institution: SAIT, School of Health and Public Safety
Course Code: DMST 244
Course Name: OB/GYN I
Module: 5
Title: OB Introduction

Developmental Stages of Pregnancy

  • Three Trimesters:

    • 1st Trimester: 0 - 12 6/7 weeks

    • 2nd Trimester: 13 - 27 6/7 weeks

    • 3rd Trimester: 28 - 40 weeks

    • Notation: "0" refers to the day of Last Menstrual Period (LMP)

1st Trimester Details

Time Frame

  • Duration: 0-12 weeks 6 days LMP (Written as 12 6/7 weeks)

Ultrasound Characteristics

  • Ultrasound Date: 23-FEB-02

  • Time: 08:40:35 AM

  • Probe: 7.0 MHz

  • Frequency: 14 Hz

  • Measurement: 70 mm

  • Power: ~0 dB, Gain = -9 dB

  • Crown Rump Length (CRL): 9.4 mm

  • Estimated Due Date (EDD): 7W OD

  • Fetal Heart Rate (FHR): 168 bpm, min: 1.6

  • Gestation Age (GA): 12w6d (yyyy/MM/dd)

Ultrasound in the 1st Trimester

Purpose

  • Confirm Pregnancy and Location: Essential for verifying the presence of the fetus

  • Viability Assessment: Establishes the fetus's health through heart activity monitoring

    • Method: Using M-mode to check fetal heart activity

  • Dating of Pregnancy: Confirms gestational age via

    • Gestational Sac (GS) Measurement

    • Crown Rump Length Measurement (CRL)

  • Determining Number of Fetuses: Identifying multiples (twins, triplets) through early ultrasound

  • Initial Visualization: First structures visible in the uterus

Importance of Accurate Dating

  • Calculating Pregnancy Duration: Originates from LMP and accounts for variations in menstrual cycles

    • Variability: Menstrual cycles longer or shorter than 28 days can lead to inaccuracies, particularly with concealed implantation bleeding

  • Timing for Tests: Specific testing and monitoring is performed at critical stages of pregnancy; incorrect dating can yield false positives/negatives

  • Milestones Tracking: Vital for assessing decisions regarding

    • Termination of Pregnancy: Timing and safety of procedures

    • Pregnancy Viability in Preterm Situations: Definition of viable gestation period

    • Due Date Calculations: Establishing what constitutes as postdates

1st Trimester Ultrasound Protocol

  • Objectives when performing ultrasound during the first trimester include:

    • Dating gestation accurately

    • Viability checks

    • Assessing for multiple pregnancies or bleeding issues

    • Identifying Gestational Sac: Distinguishing between single and multiple gestations

    • Identifying any Subchorionic Hematomas: Potential bleeding in the uterine area

    • Measuring GS: Mean Sac Diameter (MSD) until embryo visualization

    • Confirming Presence of Yolk Sac (YS): Marker of healthy fetal development

    • CRL and FHR Measurement: Once embryo is seen, measuring CRL and fetal heart rate

    • Assessing Ovaries and Adnexa: Including sac diameter checks

1st Trimester Screening

Purpose

  • Risk Assessment for Fetal Chromosomal Abnormalities: Critical screening during early pregnancy

    • Techniques:

    • Nuchal Translucency Ultrasound: Combined with maternal blood work

    • Uterine Artery Doppler assessments: For pre-eclampsia risk

  • Anatomy Scan: Limited scan for structural abnormalities

  • Timing: Conducted between 11-13 6/7 weeks

Reporting Results

  • Results are categorized as:

    • Positive (+ve): Indicates increased risk

    • Negative (-ve): Indicates decreased risk

2nd Trimester Routine Ultrasound

Timing

  • Typically performed around 18-22 weeks gestational age

Detailed Scan Objectives

  • Fetal Anatomy Assessment: Comprehensive examination during the second trimester

    • Critical Measurements:

    • Head ->

      • Biparietal Diameter (BPD)

      • Head Circumference (HC)

      • Cavum Septum Pellucidum Assessment

      • Cerebellar & Ventricular Diameter Measurement

      • Nuchal Fold and Cisterna Magna Assessment

      • Eye Orbits and Nasal Bone Checks

      • Profile & Spine Imaging

Fetal Abdomen Examination

  • Sub-Sections to Examine:

    • Abdominal Circumference Measurement

    • Stomach and Kidney Assessment

    • Cord Insertion, Bowel, Diaphragm, and Bladder Overview

Fetal Chest Examination

  • Heart Assessment:

    • Four-chamber view

    • Left and Right outflow tracts

    • Three Vessel view

    • M-mode for heart rate tracking

Additional Structural Measurements

  • Femur and Humerus Length: Key indicators of growth

  • Ankle Views: Right and Left sides imaging

  • Open Hand Assessments: Evaluations of both right and left hands

  • Placenta Location: Including distance from cervix, thickness measurements

  • Evaluation of Maternal Structures: Checks include cervix, uterus, and adnexae

3rd Trimester Ultrasound

Time Frame

  • Duration: 28 weeks to 40 completed weeks LMP

Ultrasound Goals

  • Monitoring Growth and Wellbeing: Ensuring that the placenta is functioning correctly and that the fetus is safe in utero

    • Anatomy Images: Typically not reassessed if previously reported as normal

  • Biometry Measurements for Fetal Growth:

    • Key Metrics:

    • BPD

    • HC

    • AC

    • FL

    • Fetal Heart Rate Monitoring: Using M-mode diagnostics

Biophysical Profile (BPP)

  • Components Assessed:

    • Fetal Movement

    • Fetal Tone

    • Amniotic Fluid Levels

    • Fetal Breathing Movements

    • Placental Function

Additional Placental Assessments

  • Placenta Location and Grading: Consideration of Doppler assessments if necessary

    • Monitoring circumstances such as lagging fetal growth or low amniotic fluid levels

    • Maternal Health Factors: High blood pressure and gestational diabetes implications

    • Fetal Doppler Assessments: Including umbilical artery, middle cerebral artery, and ductus venosus evaluations

Maternal Testing Protocols

Blood Work Requirements

  • First Trimester Screen: Including Nuchal translucency with consideration of Pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG)

  • 16 Weeks Testing:

    • Triple Screen or Quad Screen Testing

  • 24-28 Weeks:

    • Glucose Tolerance Screen for gestational diabetes

    • Note: Reliability compared to earlier scans is sometimes lower

Routine Doctor’s Visits

  • Visit Frequency: Progressively increasing as the pregnancy advances

    • Monthly visits during early pregnancy

    • Every 2 weeks if normal from 28 weeks until around 36 weeks

    • Weekly visits if normal until term

Monitoring Maternal Health

  • Key Aspects Monitored:

    • Weight

    • Blood Pressure

    • Urine Analysis

    • Uterine Fundal Height Measurement

    • Position of the Baby via Palpation

    • Fetal Heart Rate Recorded with Doppler

  • Post-Dates Monitoring: Ultrasounds required to assess fetal wellbeing (BPP) and growth

Course Content Outline

1st Trimester

  • Module 5: Normal

  • Module 6: Abnormal

2nd/3rd Trimester

  • Module 7:

    • Biometry

    • BPP

    • Detailed Scan

    • Fetal Lie

  • Module 8:

    • Normal Brain and Heart

  • Module 9:

    • Fetal Environment

    • Placenta and Cord

    • Multiple Gestations

  • Module 10:

    • Heredity and Chromosomal Differences