Test: Maternal physiology - NEET PG MCQ

Plasma volume increases by about 50% in a first pregnancy and 60% in subsequent pregnancies by the late third trimester.

A decrease in total peripheral resistance, dropping to about 40% by mid-pregnancy, is due to reduced afterload interpreted as circulatory underfilling, triggering compensatory mechanisms.

Cardiac output increases by 35–40% in a first pregnancy due to simultaneous increases in heart rate and stroke volume.

Progesterone drives the increase in tidal volume by lowering the CO2 threshold and increasing sensitivity in the medulla oblongata, resulting in a 30–50% rise by term.

Maternal CO2 levels drop to facilitate efficient placental CO2 transfer from the fetus, which has a higher CO2 level (~55 mmHg).

Red cell mass increases by 20–30% during pregnancy, with greater rises (~29%) when iron supplementation is provided.

Plasma fibrinogen levels double during pregnancy, contributing to the low-grade coagulopathy observed.

The glomerular filtration rate (GFR) increases by about 45% by the 9th week of pregnancy and remains stable until term.

The normal upper limit for total protein excretion during late pregnancy is 200 mg per 24-hour collection, attributed to increased GFR and altered glomerular function.

Insulin resistance in late pregnancy is primarily driven by elevated levels of cortisol or human placental lactogen (hPL), leading to higher plasma glucose levels despite increased insulin response.