26.     Physiological changes in pregnancy.

Home Page

MCQ Paper 1

Sample MCQs

 

a. blood volume increases by about 10% in pregnancy. False
b. red cell mass and plasma volume increase by similar amounts. False
c. cardiac output increases from ~4.5  to ~6 litres per minute. True
d. blood pressure is a function of cardiac output and peripheral resistance, so peripheral resistance must fall in pregnancy. True
e. the pulse rate rises in normal pregnancy. True
f. the glomerular filtration rate increases in pregnancy. True
g. the white cell count rises in normal pregnancy. True

See also MCQ1, question 43 "Iron & Pregnancy". 

Total blood volume increases by about 30% in normal pregnancy.

The increase is mainly in plasma volume ~ 50%.

The red cell mass rises, but only by about 20%.

This leads to the well-known haemodilution of pregnancy.

A bit like the publican watering the beer.

It also leads to differing views of what constitutes anaemia in pregnancy.

Nelson-Piercy in the Handbook of Obstetric Medicine says that levels < 10.5 gm. / dl. should be regarded as abnormal.

Multiple pregnancy exaggerates these changes.

 

Blood pressure does not rise significantly.

Indeed, it tends to fall in the second trimester.

So there must be a substantial fall in peripheral resistance to accommodate the increased cardiac output.

Uterine blood flow increases hugely.

And the uterine vasculature is low-resistance if trophoblastic invasion of the spiral arteries has occurred properly.

See MCQ2, question 3 "Pre-eclampsia" and MCQ10, question 1 "Trophoblasic invasion of the spiral arteries".

There is also the 50% increase in renal blood flow to reduce peripheral resistance.

 

The pulse rate rises by about ten beats per minute.

 

Renal blood flow increases by up to 50% and is reflected in lower urea and creatinine levels in pregnancy.

 

The white cell count rises during pregnancy and further in the puerperium.

Nelson-Piercy (page 311) gives figures of:

    4 11 for the non-pregnant,

    and 6 16 in pregnancy.

James (page 1680) gives figures of:

    4 9 for the non-pregnant,

    9 for pregnancy,

    and 16 for the puerperium.

The relevant units are 109 /litre.

 

Next question
Return to MCQ1, answer 43. "Iron & Pregnancy"
Return to MCQ5, answer 10. "Thrombocytopenia"

MCQ Paper 1

Return to DRCOG Page

Return to MRCOG page

List of topics covered by the MCQs

Return to "how to pass the MRCOG"

Home Page