Obstetrics - Physiology of Pregnancy

Question 1

Weight gain during pregnancy

• Causes
• Normal parameters

Answer 1

Question 2

Carbohydrate and lipid metabolism changes

• Cause
• Changes from normal
• Course

Answer 2

Question 3

Physical changes of respiratory apparatus during pregnancy

• List changes
• Causes

Answer 3

Question 4

Changes in ventilatory parameters and blood gas parameters during pregnancy

• List changes
• Causes

Answer 4

Question 5

Changes in tissue oxygenation during pregnancy
- List changes
- Causes

Answer 5

Question 6

Cardiovascular changes during pregnancy

Common CVS exam findings

Answer 6

Pregnancy changes mimics S/S of heart failure
- SOB - elevation of diaphragm, adjustments in lung volumes and RR
- Edema - ↑ total body Na and water, venous compression by gravid uterus
- Lightheadedness, syncope - ↓ venous return due to compression
- Palpitations - ↑CO in pregnancy

CVS findings:
- Sinus tachycardia
- JVP - height remains unchanged
- Peripheral pulses - ↑volume
- Atrial and ventricular ectopic beats
- Loud ± split S1, S3, ejection systolic murmur (flow murmur, from 2T onwards and disappears upon delivery)

Question 7

Changes in cardiac and vascular parameters during pregnancy

• List changes
• Causes

Answer 7

Question 8

Haematological changes during pregnancy

• Blood cell, clotting changes
• Plasma changes

Answer 8

Question 9

Renal changes during pregnancy

• Anatomical changes
• Functional changes

Answer 9

Question 10

Renal changes during pregnancy

• Electrolyte and glucose balance

Answer 10

Question 11

Gastrointestinal changes during pregnancy

• Oral
• Gastric
• Bowel
• Liver

Answer 11

Question 12

Reproductive organ changes during pregnancy

• Breast
• Uterus

Answer 12

Question 13

Reproductive organ changes during pregnancy
- Cervix
- Vagina

Answer 13

Question 14

Outline list of homrones produced by fetal-placenta unit

Answer 14

Pregnant uterus produces a wide variety of hormones!
○ Pregnancy-specific: hCG, human placental lactogen (hPL)
○ Hypothalamus: GnRH, CRH, TRH
○ Pituitary: prolactin, GH, ACTH
○ Sex hormones: estrogen, progesterone
○ Kidney: renin, angiotensin II
○ Liver: insulin-like growth factor I/II, 1,25-dihydroxycholecalciferol
○ Parathyroid: parathyroid hormone related peptide
○ Stomach: gastrin

Question 15

hCG

• Source and course
• Changes during pregnancy
• Function
• Clinical use

Answer 15

Question 16

Estrogen and progesterone

• Source and course
• Functions

Answer 16

Question 17

CRH and ACTH

• Source and course
• Function

Answer 17

Question 18

Pituitary hormones

• Changes during pregnancy
• Functions

Answer 18

↑prolactin - up to 15× normal, from anterior pituitary gland
- Stimulated - estrogen, suckling and sleep
- Inhibited - human placental lactogen (hPL) and dopamine
- Function - acts to ↑lactation (see above), relieve stress and regulate insulin secretion in post-natal period

↑oxytocin from posterior pituitary gland during labor and after delivery
- Action - myoepithelial contractions, relieve stress

Question 19

Thyroid hormones
- Changes during pregnancy

Answer 19

Thyroid
- hCG mimics TSH action
○ hCG highest in 1st trimester → TSH level is suppressed with ↑fT4 and ↓response to TRH
○ Returns normal after that
- ↑ thyroxine-binding globulin* - therefore total T3/T4 never useful in pregnancy
○ Course - occurs from 2 week and plateau by 20 weeks
○ Consequence - leads to ↑T3 + T4 production
- ↑ iodine uptake in thyroid - due to ↑iodine loss secondary to ↑GFR

Question 20

Skin changes during pregnancy

Answer 20

Hyperpigmentation (tend to regress after delivery) - usually at
- Pre-existing skin lesion, eg. moles, freckles and scars → may ↑ in size and numbers
- Normal pigmented skin areas, eg. areolae, nipples, axillae and periumbilical skin
- Along linea alba, i.e. linea nigra
- On the face, i.e. melasma

Striae gravidarum +/- pruritus of abdomen

↑Sebaceous gland activity
- Acne
- Montgomery tubercles

Hirsutism - therefore a larger proportion of hair enter telogen phase ~1-4mo after delivery
- present as massive hair shedding