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MS WordPerinatologist Corner - C.E.U/C.M.E. Modules
Preconception Counseling for Women with Diabetes and Hypertension
Sponsored by The Indian Health Service Clinical Support Center
Step 6. Hypoglycemic Agents
What about her metformin?
Is it a teratogen? While the guidelines do not sanction its use at this time, prior experience outside the United States has been reassuring as far as an absence of any teratogenic effects, when corrected for severity of the pre-pregnancy disease. It has therefore been listed as an FDA Pregnancy “Class B” drug. It does cross the placenta; however, since it only works in hyperglycemic individuals, it should not cause fetal hypoglycemia. One would think that, since it works at the “post receptor” level, and type 2 and gestational diabetes are both hyperinsulinemic states with insulin resistance, that this would be the ideal drug for such patients.
In a motivated pregnant patient, willing to exercise and follow her diet strictly, it may provide very good control, but non-adherent women will usually need supplemental insulin. It may however be very effective in lowering the total insulin dose required for such women. In Ms. RY’s case, should it be stopped, and she be started on insulin?
That is certainly the safest, and the officially sanctioned, plan, but many patients are reluctant to “start shots”. Some women may have taken it for infertility secondary to polycystic ovarian syndrome, and have conceived with it. They may have heard it reduces the incidence of miscarriage, but the evidence for that is weak. If the patient is determined to stay on it, I would just document that fact, and observe her glucose logs to see if she will also eventually need insulin.
In PCOS, use of metformin is associated with a 10-fold reduction in gestational diabetes (31% to 3%). It also reduces insulin resistance and insulin secretion, thus decreasing the secretory demands imposed on pancreatic beta-cells by insulin resistance and pregnancy.
There is almost no current evidence supporting the efficacy or safety of metformin in pregnancy, and, if the patient needs an oral hypoglycemic agent, the contemporary evidence makes glyburide a much more defensible choice…. Metformin however probably has a better infant safety profile than glyburide (less infant hypoglycemia) if the diabetic mom wishes to breast feed.
Glyburide is well known for its use in glucose intolerance that develops during pregnancy, though it is started after 13 weeks gestation. Glyburide is pregnancy class B/C.
