September 12, 2000
Family Planning, Thyroid
Question from Georgia, USA:
I am 31 and have had diabetes since age 13. I want to become pregnant soon. I also have thyroid problems and glaucoma. What are the effects of diabetes and thyroid problems during pregnancy? What are the most important months of tight control during pregnancy?
If diabetes is not controlled during pregnancy, there can be significant effects on the fetus (defects in the heart and spine for example). Resistance to insulin is increased during pregnancy, so close monitoring of blood glucose is important to maintain proper insulin dosing. To reduce the risks of diabetes to the fetus, good glucose control, in the month or so prior to conception and during the first 10 weeks of pregnancy, are essential. Fasting blood sugar should be less than 105 mg/dl [5.8 mmol/L] and one-hour after meal blood sugar less than 130 mg/dl [7.2 mmol/L].
Thyroid disease can be managed during the pregnancy. Thyroid replacement does not cross the placenta, but correcting thyroid function in pregnancy is important for neurologic development of the fetus as well as the newborn.
[Editor’s comment: It’s not clear from your letter if your thyroid condition is underactive (hypothyroid), which Dr. Jones discusses in his reply, or overactive (hyperthyroid). Treatment of hyperthyroidism during pregnancy is a bit more complicated, but is something that endocrinologists routinely deal with.