In the study, 108 3-week old infants whose mothers had low free thyroxine (Free T4) levels at 12 weeks gestation, and were compared to 96 infants born to mothers who had Free T4 levels in the 50th to 90th percentiles. According to the study, the infants of the mothers with hypothyroidism at 12 weeks gestation (this is typically toward the end of the first trimester of pregnancy) scored significantly lower on the Neonatal Behavioral Assessment Scale (NBAS) index, an evaluation used to assess neurological function in newborns. The research confirms that even mild hypothyroidism, as evidenced by low Free T4 levels in early pregnancy is a serious risk factor for neurodevelopmental problems in newborns, even as early as 3 weeks of age.
The results indicate that low thyroid hormone levels in the mother, even if they don't cause any symptoms, can have important neurological development consequences in the newborn.
Some experts are now agreeing that routine screening of thyroid function in pregnant women during the early part of the first trimester may be warranted, given these current findings.
For more information on the effects of maternal thyroid dysfunction in pregnancy, see the following selected resources:
- Fertility, Pregnancy & Thyroid Disease Information Center
- Thyroid Disease and Pregnancy: The Latest News -- Fall 2005
- Pregnant with Hypothyroidism? Increase Your Medication!!! Researchers Find Thyroid Hormone Needs Increase During Early Pregnancy -- July 2004
- New Guidelines Released Re: Thyroid Disease & Pregnancy -- May 2004
- Thyroid Guide to Fertility, Pregnancy and Breastfeeding
Source: Kooistra, Libbe, PhD et. al. "Neonatal Effects of Maternal Hypothyroxinemia During Early Pregnancy" Pediatrics, Vol. 117 No. 1 January 2006, pp. 161-167
Mary Shomon, About.com's Thyroid Guide since 1997, is a nationally-known patient advocate and best-selling author of 10 books on health, including "The Thyroid Diet: Manage Your Metabolism for Lasting Weight Loss," "Living Well With Hypothyroidism: What Your Doctor Doesn't Tell You...That You Need to Know," "Living Well With Graves' Disease and Hyperthyroidism," "Living Well With Autoimmune Disease," "Living Well With Chronic Fatigue Syndrome and Fibromyalgia," and the "Thyroid Guide to Fertility, Pregnancy and Breastfeeding Success." Click here for more information on Mary Shomon.