Hypercalcaemia and pregnancy

Hypercalcaemia is uncommon in pregnancy. Mild degrees of hypercalcaemia can be masked by the physiological decline of serum total (not ionised) calcium in normal pregnancy. Severe hypercalcaemia can cause hyperemesis, dehydration, premature contractions and neuromuscular effects, threatening both the mother and neonate. In a pregnant woman with hypercalcaemia, exclude any factors that could be contributing to hypercalcaemia (eg supplements containing vitamin D).

Evidence to guide management of hypercalcaemia secondary to hyperparathyroidism (usually due to a parathyroid adenoma) during pregnancy is lacking. Mild, asymptomatic cases can be managed conservatively with hydration and correction of electrolyte abnormalities. Bisphosphonates should not be used during pregnancy. In symptomatic or severe cases, surgical removal of a parathyroid adenoma during the second trimester is indicated.

Hypercalcaemia in pregnancy can also be caused by pseudohyperparathyroidism, a rare cause of hypercalcaemia that results from physiological release of parathyroid hormone–related protein from the placenta and breasts during pregnancy. The increased parathyroid hormone–related protein stimulates skeletal resorption. Psuedohyperparathyroidism is usually asymptomatic, with mild hypercalcaemia and suppressed parathyroid hormone on testing. Management is similar to that for primary hyperparathyroidism.

In pregnant women with hyperparathyroidism or pseudohyperparathyroidism, the fetal serum calcium concentration is even higher than the maternal concentration, and can result in suppression of fetal parathyroid function in utero. The neonate is at risk of hypocalcaemia secondary to suppressed parathyroid activity, so must be assessed for hypocalcaemia on delivery and treated if necessary.