Influence of frequency of previous pregnancies on the prevalence of thyroid nodules in women without clinical evidence of thyroid disease.

In a region with insufficient alimentary iodine supply (Kiel, Northern Germany) the prevalence of thyroid nodules was studied by means of ultrasonography in 212 healthy women (36-50 years old) in four groups of 53 women each with 0, 1, 2, and 3-5 previous pregnancies. Goiters were found in 28.3% (15 of 53) of the women without children and in 28.9% (46 of 159) of the women with children. There was no significant increase of goiter prevalence according to the number of pregnancies. We detected thyroid nodules in 21.2% (45 of 212). Only 9.4% (5 of 53) of the women without previous pregnancies had thyroid nodules, but 25.1% (40 of 159) of the women with pregnancies in the past had nodules, the difference being statistically significant (p < 0.05). We observed nodules in 11 of 53 women with 1 child (20.7%), in 11 of 53 women with 2 children (20.7%), and in 18 of 53 women with 3-5 previous pregnancies (33.9%). We propose that, in regions with borderline or insufficient alimentary iodine supply, accentuated iodine deficiency during pregnancies due to increase of iodine requirement is a probable cause for the higher prevalence of thyroid nodules in women with previous pregnancies.