In recent years, there has been an explosion in the number of adolescent pregnancies in the United States. The U.S. rate of adolescent childbearing is the highest among the industrial nations; double that of England, three times higher than in France or Sweden and nearly 20 times higher than Japan's. Each day in the United States about 1,300 babies are born to teen-age mothers.

Pregnancy in an adolescent comes at a time when she is often not ready for the responsibilities and confinement that it entails. In addition, in many adolescents, pregnancy comes before her body has matured to optimally support a pregnancy and before she is psychologically ready to accept motherhood. Finally, the support systems that usually accompany a pregnancy are often not there. The baby's father may shirk future responsibility, and the parents of the adolescent may view her pregnancy as a disaster. The girl herself often has nowhere to turn and feels guilt rather than happiness as she approaches motherhood.

Teen-age mothers have an increased risk for anemia, urinary tract infections, high blood pressure, early bleeding and complications during labor and delivery. And their infants are more likely to be born prematurely or to have grown poorly in the womb. They are far less likely than the average infant to survive.

Certainly society's goal must be to prevent adolescent pregnancy. However, in spite of many different programs aimed at prevention, the number of adolescent pregnancies remains high. Measures are necessary, in fact urgent, to ensure that an adolescent who becomes pregnant has the best chance to deliver a normal infant while at the same time continuing her own growth and development in an appropriate fashion. Among the special considerations for pregnant teen-agers are these: :: Weight gain. An adolescent must gain more weight during pregnancy than an adult woman. How much more depends on how much growth of her own can be expected during the nine months that she is carrying her baby. This will vary with the age and maturity of the teen-ager. The younger and less mature she is, the more weight she will need to gain. Maximum growth (often called the growth spurt) usually occurs early in adolescence. Thus, if an adult woman should gain 25-30 pounds during pregnancy, a 13-year-old must gain the same amount -- and perhaps another 10 pounds to cover the amount she would have gained if she were not pregnant. Iron. Certain nutrients are in short supply during adolescence, and for some these are the same nutrients that are limited dur- ing pregnancy. Probably the most important is iron. Iron requirements increase during adolescence as the body grows and must make more blood to cover its needs. Iron requirements also increase during pregnancy as the mother expands her blood supply and the fetus develops its own blood supply. Therefore, when pregnancy occurs in an adolescent, iron requirements are extremely high and iron deficiency is extremely common. All pregnant adolescents should take an iron supplement and follow a diet high in iron. Calcium. During adolescence, strong bones are being developed as calcium is rapidly deposited. Pregnancy can slow this process unless the pregnant adolescent is consuming enough calcium. Her diet must contain generous amounts of dairy foods. If this is not possible, then she should take a calcium supplement. Because all vitamins are needed in greater amounts both during adolescence and during pregnancy, the pregnant teen-ager should follow a balanced diet and take a prenatal vitamin supplement daily. Alcohol and tobacco. Both alcohol and tobacco smoke can be very dangerous to the developing fetus. Many adolescents smoke or drink; they must be convinced that continuing these habits during pregnancy is very dangerous. They must be helped to stop -- a difficult task for anyone and particularly for a teen-age girl who is pregnant and possibly uncertain and frightened of the future. Drugs. Recreational drugs, of course, are dangerous to the mother and fetus. For the pregnant adolescent on drugs, an extensive treatment program is needed to help her stop.

Myron Winick, MD, is the Williams Professor of Nutrition at the Columbia College of Physicians and Surgeons, Columbia University, New York.