Haemoglobin

g/L · Full blood count & differentials

Haemoglobin carries oxygen in red cells — the headline marker for pregnancy anaemia screening.

Physiological haemodilution lowers concentration in the second trimester even when iron status is adequate. Values below local pregnancy thresholds trigger further iron studies.

How to read it

Interpret alongside ferritin and MCV: microcytic patterns suggest iron deficiency; normocytic low Hb may reflect dilution or mixed causes.

Trimester context

Stage	For the mother	For the baby
First trimester	Baseline establishes pre-dilution status.	Early hypoxia risk is low but maternal symptoms matter.
Second trimester	Dilution nadir — many guidelines use lower Hb cut-offs than non-pregnant adults.	Rising fetal oxygen demand tracks placental growth.
Third trimester	Pre-delivery optimisation reduces transfusion risk.	Iron accretion continues until term.