metabolic changes

Last reviewed 01/2018

During pregnancy there is an increase in metabolic rate which is largely due to the demands of the fetus. Thyroid gland hypertrophy occurs in about 70% of pregnant mothers and there is an increase in oxygen consumption of about 20% in pregnancy.

The secretion of human placental lactogen - HPL - by the placenta affects the mother's carbohydrate metabolism. This hormone acts as an insulin antagonist and thus raises the maternal blood sugar levels. The action of HPL causes the mother to require increased levels of insulin to be produced by her own pancreas. Thus pregnancy may sometimes cause the exposure of previously latent diabetes.

There is a net increase in protein production during pregnancy and this indicates that the mother must have a high protein diet.

The main source of energy for the mother during pregnancy is fat and thus the levels of blood lipid are seen to rise during pregnancy.

The average weight gain that should occur during pregnancy is about 12.5 kg or 28 lb. The majority of the weight gain is during the latter half of pregnancy.

Note that as regards metabolism of drugs, there is an increase in the maternal hepatic clearance of drugs.