Decreased birth weight, length, and head circumference in children born by women years after treatment for hyperthyroidism.

Context: Whether hyperthyroidism influences the birth characteristics of children born several years after treatment is unknown. Objective: The objective of the study was to compare birth characteristics in singleton newborns delivered by women previously treated for Graves' disease (GD), toxic nodular goiter (TNG), or nontoxic goiter (NTG). Design: This was a nested case-control design within a national cohort registry study from 1950 through 2006. Setting: The study was conducted at a university and a hospital center in collaboration. Patients: The birth characteristics of newborns (n = 3421) delivered in a cohort of 43 633 women treated for GD or toxic nodular goiter by radioiodine or surgery (exposed group) at least 1 year prior to pregnancy were compared with newborns (n = 2914) of 45 655 mothers, previously operated for NTG (unexposed group). Main Outcome: The primary outcome was birth weight, length, and head circumference. The secondary outcome was malformations, gestational age, and type of hyper...