MD Notes

creation date: 2024-12-29 14:25
tags: Anatomy & Physiology Incomplete

Uncomplicated Pregnancy

First Trimester (Wk 1+0 - 12+6)

Fetal Development

Maternal Changes

Changes include:

  • Increased oxygen consumption
  • Decreased maternal immune response
  • Increased cardiac output and blood volume
  • Anabolic metabolism in early pregnancy
  • Increased insulin resistance
  • Increased weight, joint mobility, and ligament stretch

Breast changes
By week 6-8:

  • Engorgement
  • Tenderness
  • Nipple changes/darkening
  • Visible veins

Placenta

Clinical Components

Notable Conditions

Nausea and vomiting

  • Develops week 5, worst at week 9, and improves week 16
  • 50-80% develop nausea, 50% nausea and vomiting, 1% develop hyperemesis gravidarum
  • Red flags: >2-3 episodes per day, dehydration, weight loss, vaginal bleeding, cramps, unable to eat/drink, fever, diarrhea, mental health
  • Management:
    • Lifestyle - frequent/small meals, high protein/low fat, bland, hydration, avoid triggers
    • Rule out other conditions prior to pharmacological treatment
    • Vitamin B6 (anti-nausea)
    • Doxylamine (anti-emetic) ± gravol
    • Hospitalization for IV fluids and enteral/parenteral nutrition

Indicated Testing & Investigations

First prenatal appointment
Blood tests:

  • Blood type and Rh factor
  • Rubella immunity
  • CBC (anemia/iron deficiency)
  • Hep. B serology (risk of asymptomatic transmission to infant)
  • VDRL (syphilis)
  • HIV testing
  • STI testing
  • Blood disorders if high risk

Simple in-office calculations:

  • Gestational age = time since last menstrual period
  • Fetal age = time from conception date (~2 weeks less than gestational age)
  • Estimated date of confinement (EDC) = ~280 days gestational age (Naegele’s rule)

Dating ultrasound (week 6-10):

  • Accurate estimation of gestation age using crown-rump length (GA 7-10 weeks)
  • Cardiac activity and anatomy

Genetic Testing
Enhanced First Trimester Screening (eFTS):

  • Consist of an ultrasound (nuchal translucency) and bloodwork (hCG, PAPP-A, AFP)
  • Between GA 11+2 – 13+3 weeks

Non-Invasive Prenatal Testing (NIPT):

  • Very sensitive and specific testing through fetal/placental DNA testing from maternal blood
  • Available week 9+, for specific indications (or out of pocket cost)
  • Also provides gender determination

Routine Interventions & Management

Second Trimester (Wk 13+0 - 27+6)

Fetal Development

24 weeks is point of viability - difficult to abort after

Maternal Changes

Symphysis-Fundal Height
After 20 weeks, SFH is commonly measured during prenatal appointments as it is an approximation of fetal growth and amniotic fluids. This is the distance from pubic bone to top of uterus.

Between 20-36 weeks:

  • SFH approximates number of weeks gestation

Breast changes
At week 16-18 onwards, colostrum may begin production

Clinical Components

Notable Conditions

Indicated Testing & Investigations

Genetic Testing
Second Trimester Screening (STS):

  • Similar to eFTS if it was missed

Gestational Diabetes Testing

  • Screening for asymptomatic GDM is done through glucose challenge and tolerance testing. A two-step approach is preferred but one step tolerance test is also available.
  • Done during GA 24-28 weeks; consider doing it <20 weeks if high risk

Routine Interventions & Management

Vaccinations

  • RhoGAM for Rh- mothers at 26-28 week and within 72 hours of birth of Rh+ baby
    • Note: if at any point there is suspicion of mixing, give RhoGAM immediately and then ever 12 weeks until birth
  • Tdap at 27-32 week
  • Hep B if no immunity or high risk

Third trimester (Wk 28+0 - birth)

Fetal Development

Maternal Changes

Clinical Components

Notable Conditions

Some notable symptoms/conditions near end of pregnancy include:

  • Increase in skin temperature
  • Increased urine frequency
  • Swelling
  • Hair growth
  • Braxton-Hicks contractions
  • Stretch marks and dry skin
  • Colostrum production
  • Constipation
  • Vaginal discharge
  • Hemorrhoids (due to increased intraabdominal pressure)
  • Decreased libido

Indicated Testing & Investigations

Maternal Investigations
VDRL for syphilis

  • False positives can come from Viral infections, Drugs, Rheumatic fever, Lupus/Leprosy

Group B Streptococcus

  • Routine at week 36 – 37+7 or prior to labour if early
  • Positive culture indicates prophylaxis
  • Negative test is valid for 5 weeks before a repeat swab is needed

Symphysis Fundal Height (SFH)

  • Confirm it matches gestational age (should be ~ cm = week between week 24-36 GA)

Fetal Investigations
Non-Stress Test (NST)

  • Measures how fetal heart rate responds to fetal movement
  • Non-reactive may suggest hypoxia, sleep, or gestational age too early

Biophysical profile

  • Ultrasound for fetal movement, tone, breathing, amniotic fluid volume

Anatomy ultrasound

  • Ultrasound for brain structure, umbilical cord, biometry, and that size corresponds to gestational age

Routine Interventions & Management

Vaccinations
RSV

  • Available week 32-36
  • Infant version is typically better and given to the infant 48-72h after birth

RhoGAM
For Rh- mothers, given IV or IM:

  • Routine at week 26-28
  • Within 72 hrs of birth of Rh+ baby

If any suspicion of blood mixing (eg. following a MVA), RhoGAM is given every 12 weeks until birth. If abortion or miscarriage, one dose is given if GA ≥8 weeks.