Singapore, like other newly industralized countries, has seen a dramatic transformation in the social standards of its population in a particularly short space of time. Unfortunately, this period of development has been accompanied by an escalation in the number of pregnancies to unmarried teenage girls. This paper examines the obstetric and social implications of 150 such pregnancies in younger and older teenagers. Poor intrauterine growth in the younger teenager appears to be the most important adverse obstetric outcome in that mean birthweight was significantly reduced (2738 g compared to 3054 g; P less than 0.02). We believe this to be an important explanation for the five-fold increase in perinatal mortality seen in this group of mothers. Unlike some other reports, we found no significant increase in the incidence of cephalopelvic disproportion, anemia or pregnancy induced hypertension in these mothers. The social implications of teenage pregnancy in Singapore are also examined and recommendations made for methods to curb the problem.