Every Tuesday, TriangleMom2Mom's expert panel answers questions about your kid's health, your health and related issues. If you have a question, send it to me.

Today, Alice Chuang, MD, FACOG, assistant professor of obstetrics and gynecology at the N.C. Women's Hospital, fields a question from a mom with gestational diabetes.

The question: I have gestational diabetes and my doctor has recommended that I get a C-section two weeks before my due date. Is this standard procedure? How big is too big for a baby?

The response: Performing a C-section at 38 weeks gestation, two weeks before the due date, is NOT what is typically recommended for gestational diabetics. There are two issues here....when to deliver and how to deliver. Let me try to tackle them separately.

First, when to deliver...

Sometimes early delivery is necessary for fetal health and for maternal health because of an acute issue. These situations cannot be avoided and a physician should use his or her best judgement to weigh the risks of prematurity with the fetal and maternal health.

In general, diabetic or not, elective delivery, meaning a delivery that is being planned when both mother and fetus are stable, either by C-section or induction of labor, should not be performed prior to 39 weeks. All fetuses are at risk for respiratory complications, specifically respiratory distress syndrome. The later in gestation a fetus is born, the less likely this will occur. Even at 37-38 weeks, at a gestation that is generally considered "full term," 1 percent to 3 percent of infants have respiratory problems. At 39 weeks, the risk is around 1 percent.

Per the American College of Obstetrics and Gynecology, (ACOG) "fetal pulmonary maturity should be confirmed before elective delivery at less than 39 weeks of gestation unless fetal maturity can be inferred from any of the following criteria," (ACOG Educational Bulletin, No. 230, Nov 1996) and they go on to describe certain criteria which ensure that a pregnancy is actually dated correctly and is truly 39 weeks. There are tests for fetal lung maturity, all of which require amniocentesis. So for example, and this is a real example, we had a patient who was planning for a repeat Cesarean section (she was delivered by C-section for her first pregnancy). She wanted her repeat C-section scheduled for about 38 weeks and 4 days secondary to her family's schedule and planning flights into town, etc. We counseled her about the risk and the recommendation against this per ACOG unless she first had an amniocentesis to be sure her fetus's lung were mature. She opted for amniocentesis. The tests confirmed that her fetus's lungs were ok, and we delivered her prior to 39 weeks.

Unfortunately, fetuses of diabetic mothers have delayed lung maturity making this an even more important issue for this patient. Her fetus at 38 weeks, because she is diabetic, is more likely to have respiratory complications than the fetus of a non-diabetic mother at the same gestational age. In a stable diabetic, delivery at 38 weeks is not recommended unless amniocentesis first can confirm fetal lung maturity.

Now...how to deliver...

Maternal diabetes alone is not a reason for C-section, but the answer is a bit more complicated than that.

Macrosomia is the medical term for a baby that is "too large" or specifically 4000-4500 g which is 8 pounds 15 ounces to 9 pounds 9 ounces. The issue of size is generally not important if a C-section is being planned. It really has to do with the issue of vaginal delivery. The larger a baby is, the more difficult to achieve a successful vaginal delivery for all women. Some women can birth larger babies than others. There is such a thing as an infant who is too big to deliver vaginally. Diabetic babies tend to be larger, particularly if the diabetes is not well-controlled through the pregnancy. Larger babies can result in more difficult vaginal deliveries. The only problem is that our methods of estimating fetal weight are poor. These methods include guessing by physical exam, doing an ultrasound and asking the mother herself. When all of these methods are compared, second-time mothers can be better than physicians, using either physical exam or ultrasound, at guessing the weight of their second child. The bottom line is that it is difficult to acurately determine if a fetus is too large to be delivered vaginally by a mother.

ACOG does have a weight limit for vaginal deliveries. They state "Although the diagnosis of fetal macrosomia is imprecise, prophylactic cesarean delivery may be considered for suspected fetal macrosomia with estimated fetal weights greater than 5,000 g in women without diabetes and greater than 4,500 g in women with diabetes. " (ACOG Practice Bulletin No. 22, Nov 2000) "Prophylactic" refers to a C-section which is done without any attempt at vaginal delivery.

So given all of this, you would have to assess whether the mother's disease was in good control and how big the baby was before you made any type of decision about when and how to deliver. Per ACOG, in the diabetic patient, if you felt with the best data you had that the fetus was greater than 9 pounds 9 ounces, than you could outright offer the patient a C-section with no vaginal delivery attempt. It should be offered at 39 weeks. If offered prior to that, fetal lung maturity tests should be performed.

Remember that medicine is an art and even though there are guidelines and rules, each patient is an individual, and each medical situation must be carefully considered.

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