How common is hyperthyroidism in pregnancy?

Hyperthyroidism is found in 1-2 per 1000 pregnancies. The most common form is Graves’ disease.

What are the risks of hyperthyroidism to the mother and the foetus?

Hyperthyroidism is associated with:

• premature birth
• miscarriage in the early stages of pregnancy
• pre-eclampsia
• intrauterine growth retardation
• fetal goiter
• foetal hydrops
• foetal and neonatal hypothyroidism
• congestive foetal heart failure
• foetal and neonatal hyperthyroidism
• stillbirths

As Graves’ disease-specific antibodies cross the placenta they can cause:

• fetal goitre, but also
• transient neonatal hyperthyroidism

How should the mother with hyperthyroidism and the newborn be treated?

The treatment of hyperthyroidism in pregnancy is complex and the intervention of the endocrinologist must be immediate and accurate in order to avoid the consequences of both hyperthyroidism and improper treatment. Indeed, antithyroid drugs cross the placenta and improper dosage can lead to fetal goitre and hypothyroidism to congestive heart failure and mental retardation of the new-born. The neonate should be monitored closely after birth for hypo- or hyperthyroidism and treated promptly.