[HD 201] E02-T02-Maternal Adaptation_ Hematologic, Reproductive System, Metabolism (1)_compressed

Introduction

• Pregnancy causes physiological changes to the female body's organ systems, facilitating fetal development.
• Most organ systems adapt accordingly.

Reproductive System: Uterus

• The uterus stretches and expands during pregnancy.
• Wall thickness decreases for the fetus to become palpable

Three Muscle Layers:

• Outer Longitudinal Layer: Hood-like, arches from the fundus to ligaments and aids contractions as well as retraction during labor for fetal expulsion.
• Middle Oblique Layer: Criss-cross fibers are perforated by blood vessels in a "Figure of 8" to constrict them, control bleeding after delivery (hemostasis).
• Internal Circular/Sphincter Layer: Transverse, located deep within the myometrium as sphincters around orifices (cervix/fallopian tubes).
• The Internal Circular/Sphincter Layer is the weakest and where C-sections occur due to the thin wall and lack of uterine contractions.

Uterine Size Changes:

• Non-pregnant uterus length increases from 8 cm to 30 cm during pregnancy.
• Non-pregnant uterus width increases from 5 cm to 22 cm during pregnancy.
• Non-pregnant uterus depth increases from 2.5 cm to 20 cm during pregnancy.
• The wall thickness of the uterus decreases from 1.5 cm to 2 cm during pregnancy, making the fetus easier to palpate.
• Non-pregnant uterus weight increases from 70 g to 1100 g (1.1 kg or 2.4 lbs) during pregnancy.
• Non-pregnant volume increases from 0.05 L to 5-20 L during pregnancy.
• Uterus length is about 6-8 cm in non-pregnant women, 4 cm in pre-pubertal women, and 9-10 cm in multigravida women.
• The uterus wall thins out during late pregnancy stages.

Factors Influencing Enlargement:

• Actual Growth: Enlargement (hypertrophy) of existing cells, stimulated by estrogen and progesterone. Appearance of new muscle cells (hyperplasia) as well as accumulation of fibrous and elastic tissue for elasticity
• Stretching: Pressure from expanding products of conception, such as the fetus
• Placenta site: Myometrium enlarges more rapidly where the placenta is implanted.

Uterine Shape Changes:

• Early Pregnancy: Transforms from pyriform (pear-shaped) to globular
• End of 3rd Month: Becomes spherical, extends from the pelvis. Begins to rotate to the right, or dextrorotate, because of the rectosigmoid. Returns to pyriform.
• After the 5th Month: Ligaments maintain the uterus's position to prevent twisting inside the abdominal cavity.
• Beyond 36 Weeks: Changes to spherical

Fundal Height:

• Measured from the pubic bone (symphysis pubis) to the top of the fundus to assess fetal growth, estimate gestational age, and provide information about amniotic fluid.
• Fundus becomes palpable just above the pubic symphysis at 12 weeks.
• Fundal height usually correlates from 20-34 weeks of gestation.

Fundal Height Timeline:

• 12 weeks- Just above the symphysis pubis
• 16 weeks- Located halfway between the umbilicus and symphysis pubis
• 20 weeks- At the level of the umbilicus
• 36 weeks- At the highest point
• 40 weeks- Goes down at the expected delivery time

Other uterine corpus changes

• The normal anteversion and anteflexion disappears
• Right obliquity or rotation shifts to the right
• Arteries, veins, and lymphatics enlarge
• Uterine ligaments thicken
• Progressive increase occurs in uteroplacental blood flow of 450 ml/min in the mid-trimester, and increases to 500-750 ml/min at 36 weeks
• In atony after birth, a patient can lose 1 L of blood after two minutes leading to shock in minutes

Blood Flow:

• Left and right uterine arteries supply the uterus.
• Arcuate Arteries: Branch from the Uterine Arteries to run within the outer and middle thirds of the muscle.
• Radial Arteries: Branch from the Arcuate Arteries, directing toward the lumen.
• Spiral Arteries: Branch from the Radial Arteries into the intervillous space.
• Rich anastomoses of these vessels to accommodate the growing fetus.

Diagrammatic representations

• Non-gravid artery walls contain large quantities of smooth muscle with autonomic innervation
• Normal pregnancy anastomoses supports increased blood flow to the placenta via uterine to arcuate, radial, and spiral arteries and capillary plexuses
• The anastomoses remain after birth, reflecting blood flow adaptation
• Narrowing of vessels contributes to fetal growth restriction with minimal arterio-venous shunts, high pressure with low blood flow which lowers oxygen delivery

Measurement Accuracy:

• Impacted by obesity, amount of amniotic fluid, number of gestations, and fetal lie/attitude.
• Transverse lie result inshorter fundal measurement

Above 36 Weeks:

• Engagement of presenting baby.
• Baby is positioned to be delivered, lowering the fundal height.
• 40-week pregnancy measures smaller than a 36-week pregnancy ("Lightening during pregnancy").
• Muscle tone of abdominal wall.
• Laxisity may affect height
• Muscular rigidity can make it difficult to palpate
• Obliquity causes uterus and its measurement to be lower
• Accuracy increases as uterus gets larger

Contractility

• Contractions may not always be painful
• Assessed based on tightness of underwear

Braxton-Hicks Contractions:

• Discovered in 1872
• False labor contractions

Braxton-Hicks Vs. True Labor Contractions:

• Braxton Hicks: After 20 weeks, irregular with long intervals, weak or weakening
• True Labor: At 37 weeks, regular with shortening intervals and increasing strength

Cervix

• Softening of cervix
• Increased mucus production of whitish hue
• Cervical mucus consistency changes
• Eversion occurs
• Cervical glands appear hypersecretory Softening Softening occurs one month after conception Assess with a gynecological exam Related to increased vascularity, edema liquefication of collagen, hypertrophy and hyperplasia

Cervical Mucus production

• Complaints of secretions are common
• Normal color is whitish and opaque
• Color may be yellow, green, or gray

Plug

• Immunological defense
• Blocks conception from infection
• Patient expels plug

Consistency

• Changes occur
• Cervical mucus is tested via glass slide

Beading and Ferning processes

• Beading- Related to progesterone
• Ferning- Related to elevated levels of oestrogen and amniotic fluid

Additional Knowledge

• Hegar's Sign: Softening of uterus and the isthmic junction
• Chadwick's Sign: Bluish cervix due to elevated vascularity

Eversion

• Proliferation occurs out and moves into the ectocervix

Endocervical gland

• Intraglandular can be striking
• Important to note signs of possible carcinoma

Ripening

• Cervical collagen decreases
• Water content raises

Ovaries

• Limited ovarian changes during pregnancy
• Corpus luteum of pregnancy
• Relaxin Secretion in theca lutein cysts

Corpus luteum of pregnancy

• Enlarges due to hCG
• Retains the pregnancy and produces estrogen
• Important to retain prior to the 7th week

Relaxin

• Secreted by the corpus luteum, as well as the decidua and placenta
• aids in remodeling through vasodilation and increased GFR

Theca Lutein Cysts

• Reflects amplified physiology to elevated serium HCG
• Do not interfere with the foetus

Fallopian Tubes

• Limited changes occur
• Decidual reaction might occur

Vagina

• Great vascularity occurs
• Edema may be present

Changes

• The vaginal pH varies from 3.5 to 6 as lactic acid production elevates through carbohydrate storages
• Elevated risk for yeast infections
• Vaginal hypertrophy occurs

General

• Uterine volume expands drastically
• Evaluate fundal height
• Test for Chadwick's sign
• Theca Lutein cells are hyperactive and require non-interference

Carbohydrate Metabolism

• Metabolic effects of pregnancy
• Influencing overall metabolic output
• Fetal aspect: Fufilling growth
• Maternal factors: Meeting demands

Basal Metabolic Rate (BMR)

• 3rd trimester- BMR elevates higher for the non pregnant woman
• Twin pregnancy- elevate BMR to around 20%
• Elevated body temperature
• Greater energy demand

Total Pregnancy (kcal) and Trimester

• Estimated total pregnancy energy demands is at 77,000 kcal
• 1st trimester: 85 kcal/day
• 2nd trimester: 285 kcal/day
• 3rd trimester: 475 kcal/day
• women should have an + 300 kcal per day

General points

• Women typically gain weight without intake
• The correct intake should be based on 2100 kcal a day
• Fat mass increases
• Greater weight gain needed for underweight patients

Weight Gain

• Total weight gain for entire pregnancy: 12.5 kg
• BMI during pre-pregnancy must is important to determining weight gain itself