Changes In Maternal Physiology During Pregnancy

From Conservapedia

There are a number of changes in maternal physiology during pregnancy that are summarised in this article.

Weight Gain[edit]

Blood volume

Total blood volume increases by 1.5L (40%)
Total plasma volume increases by 1.25L (45%)
Total red blood cell mass increases by between 240ml (18% - without iron supplements) and 400ml (30% - with iron supplements)
- Haemocrit falls (40% to 31%)
- Haemoglobulin concentration falls from 13.5% to 11-12%
- Results in dilutional anaemia of physiological anaemia of pregnancy
White blood cell concentration increases from 7000/ul to 10-11,000/ul
Platelet turnover increases
Total plasma proteins increase, but concentration decreases
Globulin increases, albunin:globulin ratio falls

Cardiac Output

Cardiac output increases by approximately 1.5L/min
- Stoke volume increases from 64ml to 71ml
- Heart rate increases from 70bpm to 85bpm
Total peripheral resistance falls
Blood pressure falls during first trimester, but returns to normal by term

Cardiac distribution

Increased flow to:

Venous pressure in lower body increased due to:

Increased blood flow (40%)
Increased plasma flow (45%)
Increased glomerular filtration rate (50% - due to increased plasma flow and reduction in colloid osmotic pressure)

Increased sodium retention (largely due to activation of renal angiotensin system)

In bladder frequency (both day and night)
- Due to increased GFR, compression by uterus and hyperaemia
- severe by week 6 then subsides until late pregnancy

Minute ventilation increases
Respiratory rate constant
Tidal volume increases - promoted by softening of thoracic ligaments and rising of diaphragm by 4 cm
Functional residual volume decreases (reduces dilution of breath)

Progesterone induces cravings
Increased absorption of calcium and iron
lower and upper intestines raised
decreased motility of GIT (increased absorption, but leads to constipation)
reduced tone of lower oesophageal sphincter (due to progesterone, leads to heartburn)
increased volume and contraction of gull bladder (leads to kidney stones)

Metabolism increases in general. Changes in:

Carbohydrates (decrease in glucose levels in first trimester, increase in insulin resistance in third trimester due to human placental lactogen - induces metabolism of fat into glycogen which is diffused over placenta, but increases peripheral insulin sensitivity)
Proteins (amino acid concentration falls due to active transport over placenta, require high fibre diet to compensate)
Fat (fatty acids become main energy source and stores increase by 4 kg)