Mastering the many complications of pregnancy in the obese patient. (VBAC Especially Risky in this Population).

SARASOTA, FLA. -- Obesity is the most common chronic condition complicating pregnancies in developed countries.

Up to 10% of pregnant women are obese, weighing at least 200 pounds, and up to 3% are massively obese, weighing at least 300 pounds, Dr. Haywood L. Brown said at a perinatal symposium sponsored by Symposia Medicus.

Chronic hypertension, gestational diabetes, preeclampsia, pregestational diabetes, obstructive sleep apnea--and all the adverse effects such conditions can have on a fetus--are among common complications that occur more in obese women than in women of normal weight, said Dr. Brown, professor and chair of the department of ob.gyn. at Duke University, Durham, N.C.

Furthermore, evidence suggests that obese women are at greater risk of having babies with birth defects, particularly neural tube defects. Folate deficiency, which is common in obese patients and is a factor that contributes to increased risk for neural tube defects, may be partly to blame, he said.

Complicating the matter is the difficulty in using diagnostic imaging in obese women. Image quality with ultrasound for aneuploidy screening can be quite poor due to tissue density and decreased velocity in traveling sound waves. One possible solution is to use a transvaginal probe in the umbilicus.

This technique requires practice, and it is important to counsel patients that imaging is less than ideal under such circumstances, but it may offer some advantages for viewing the heart and other structures or even for simpler tasks such as identifying the baby's position.

Given the increased risks for complications and difficulties in prenatal diagnosis, it is not surprising that adverse outcomes are also more common with obesity, Dr. Brown said. In one study of nearly 168,000 women, obese gravidas were found to have a higher risk of late neonatal death and, at least among nulliparas, a higher risk of very pre-term delivery.