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Journal of Thyroid Research
Volume 2014, Article ID 160780, 5 pages
Research Article

Maternal Hypothyroidism in Early Pregnancy and Infant Structural Congenital Malformations

1Tornblad Institute, Lund University, Biskopsgatan 7, 223 62 Lund, Sweden
2National Board of Health and Welfare, 10630 Stockholm, Sweden
3Karolinska Institutet, Department of Medicine, Centre for Pharmacoepidemiology, 17176 Stockholm, Sweden

Received 27 November 2013; Revised 9 January 2014; Accepted 9 February 2014; Published 12 March 2014

Academic Editor: Noriyuki Koibuchi

Copyright © 2014 Bengt Källén and Birgitta Norstedt Wikner. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Background. The question is debated on whether maternal hypothyroidism or use of thyroxin in early pregnancy affects the risk for infant congenital malformations. Objectives. To expand the previously published study on maternal thyroxin use in early pregnancy and the risk for congenital malformations. Methods. Data from the Swedish Medical Birth Register were used for the years 1996–2011 and infant malformations were identified from national health registers. Women with preexisting diabetes or reporting the use of thyreostatics, anticonvulsants, or antihypertensives were excluded from analysis. Risk estimates were made as odds ratios (ORs) or risk ratios (RRs) after adjustment for year of delivery, maternal age, parity, smoking, and body mass index. Results. Among 23 259 infants whose mothers in early pregnancy used thyroxin, 730 had a major malformation; among all 1 567 736 infants, 48012 had such malformations. The adjusted OR was 1.06 (95% CI 0.98–1.14). For anal atresia the RR was 1.85 (95% CI 1.00–1.85) and for choanal atresia 3.14 (95% CI 1.26–6.47). The risk of some other malformations was also increased but statistical significance was not reached. Conclusions. Treated maternal hypothyroidism may be a weak risk factor for infant congenital malformations but an association with a few rare conditions is possible.