Dear Doc:

I am 27 weeks pregnant.  Yesterday I received a call from my doctor’s office telling me that I had “failed” my glucose testing and I need to complete a three-hour long test to determine if I have diabetes.  This is my third pregnancy and I never had diabetes before.  Why do women get diabetes in pregnancy?  If I do have it, what are the risks to my baby?

Dear Reader:

There are many factors that contribute to the development of gestational diabetes (GDM).  Normally when a woman eats, her pancreas produces the perfect amount of insulin to keep her blood sugar normal.  In pregnancy, the growing fetus needs sugar from the mother. To meet this need, the placenta produces a hormone called human placental lactogen (HPL).  As the pregnancy progresses, the placenta grows and the amount of HPL produced increases.  The HPL prevents the woman’s body from responding as well to the insulin produced by the pancreas, leaving more sugar for the baby.  For the vast majority of women this process allows the baby to receive what he or she needs, and the mother maintains a normal blood sugar by producing more insulin.  If the pancreas in unable to make enough insulin to keep the women’s blood sugar normal, she develops diabetes.    

Every pregnant woman should be screened for diabetes in the third trimester between 24-28 weeks.   There are different ways of doing this test, but the most common screening test is a one-hour glucose tolerance.  The woman drinks a 50g glucose solution and her blood sugar is tested one hour later.  If that blood sugar level is above 140mg/dL (or 130 mg/dl depending on the cutoff used by your lab) then the woman is asked to complete a three-hour test.  In the three-hour test, the woman’s blood sugar is tested while fasting and again one, two and three hours after drinking a 100g glucose solution.  If two of those four values are elevated, the woman is considered a gestational diabetic. 

In the Unites States between six and seven percent of pregnancies are complicated by diabetes and about 90 percent of those are women who develop diabetes during the pregnancy (GDM).  Women who are obese, have a history of gestational diabetes, or have a history of insulin resistance (for example some women with polycystic ovarian syndrome) are at higher risk of gestational diabetes.  It is recommended that these women undergo screening in the first trimester and again between 24-28 weeks. There has been a steady increase in the rate of gestational diabetes as Americans grow more obese and sedentary.   

According to the US Preventative Service Task Force and the American College of Obstetrics and Gynecology, treatment of gestational diabetes has been found to reduce the risk of complications such as preeclampsia (a condition that can lead to seizures and strokes), large babies (over 4,000g), shoulder dystocia (where the baby’s shoulders are stuck in the birth canal) and the need for cesarean delivery.   For these reasons it is critical that we identify and treat women with this condition.  Initial treatment often includes nutritional counseling along with home glucose monitoring.  Most women with GDM will be able to normalize their blood sugar levels with healthy changes to their diet and exercise regimen.  Some women will require medication either as an oral hypoglycemic or injections of insulin.  It is not uncommon for the doses of medication to be changed frequently during pregnancy in response to the changing hormone levels.   It is critical for the woman to be seeing her medical provider frequently during this time.

While it is not possible to prevent all cases of gestational diabetes, we know that there is a lot that we can do to reduce the risk.  The most important factor is obesity.  Women planning for pregnancy should work to be a healthy weight prior to conception.  It is also important to get regular cardiovascular exercise prior to pregnancy and to maintain an exercise regimen in consultation with a medical provider during the pregnancy. 

Tara Gellasch, MD, is the Chief of Obstetrics and Gynecology at Newark-Wayne Community Hospital (NWCH) and sees patients at The Women’s Center at NWCH, a Rochester General Medical Group practice.  Dr. Gellasch earned her Medical Doctorate from McGill University in Montreal, Quebec and completed her residency in Obstetrics and Gynecology at Emory University. This column is meant to be educational and not intended to be used to make individual treatment decisions. Prior to starting or stopping any treatment, please confer with your own health care provider. To send questions on women’s health, please email Dr. Tara Gellasch’ s assistant, Monica Decory at Monica.Decory@rochesterregional.org and write “Ask a Doc” in the subject line. The Women’s Center at NWCH is located at 1250 Driving Park Avenue, Newark. Call (315) 332-2427 to schedule an appointment.