The potential of mid-trimester maternal plasma alpha-fetoprotein measurement in predicting infants of low birth weight.

Maternal plasma alpha-fetoprotein (AFP) was measured at mid-trimester in 113 women who subsequently were delivered of a singleton liveborn infant weighing less than 2.5 kg and in 113 matched controls whose infants weighed more than 2.5 kg. Plasma AFP levels were significantly higher in the subjects than in the controls, while 10 of the subjects and only 3 of the controls had values above 2.0 times the median. The higher AFP concentrations were seen both in pregnancies in which the outcome was a small premature infant and in those in which it was a small-for-dates baby.