Factors that affect maternal insulin resistance and modify fetal growth and body composition.

Fetal growth is multifactorial and can be altered by a variety of extrinsic and intrinsic factors. The maternal, placental, and fetal contribution to growth must all be considered. Of particular interest are maternal metabolic regulation and the availability of nutrients to the developing fetus. Weight gain, hyperlipidemia, and insulin resistance occur as a normal adaptation to pregnancy. Obesity and underlying insulin resistance among women of reproductive age are rapidly increasing, and the contribution of pregnancy on this abnormal metabolic background poses additional maternal and fetal challenges. Many components of the metabolic syndrome have been associated with changes in fetal growth, including obesity, dyslipidemia, hypertension, and insulin resistance or glucose intolerance. Additional factors affect fetal growth and include diet, exercise, and smoking. In this review, we briefly discuss the importance and descriptions of fetal growth, followed by a discussion of several of the extrinsic and intrinsic established factors affecting fetal growth. We highlight factors that may modify fetal growth and body composition directly or indirectly through alterations in maternal metabolism.