Reduced insulin sensitivity in adult life has been reported in subjects born at term small for gestational age (SGA) and in those born prematurely with very low birth weight (LBW) (<1,500 g). We assessed whether LBW (<2,500 g) young women, irrespective of whether they were born SGA or adequate for gestational age (premature AGA), exhibited a reduction in insulin sensitivity through a prospective historical design. The risk of developing biochemical and clinical features of polycystic ovary syndrome was also investigated. The study population included 35 LBW women (19 SGA [BW range, 1,000-2,400 g] and 16 premature AGA [BW range, 1,700-2,440 g]) aged 21.8 +/- 1.8 years and 35 term AGA controls, of similar age, recruited from a neonatal registry. All women underwent clinical, ultrasonographic, hormonal, and metabolic evaluations, including the composite insulin sensitivity index. Women under hormonal contraception (21.4%) were excluded from hormonal and metabolic analyses. Composite insulin sensitivity index was significantly lower in LBW women even when the 2 LBW subgroups, SGA and premature AGA, were analyzed separately (4.4 +/- 2.2 and 4.0 +/- 1.7, respectively) than in controls (6.9 +/- 4.4). The LBW women showed a significantly higher incidence proportion of irregular menses (14/35 [40%] vs 2/35 [5.7%]) and a significantly higher free androgen index (5.8 +/- 3.5 vs 3.9 +/- 3.2). They also showed a nonsignificantly higher proportion of hirsutism, acne, and polycystic ovaries. In conclusion, LBW (<2,500 g) young women, irrespective of whether they were SGA and premature AGA, exhibited a reduction in insulin sensitivity as compared with born at term AGA women. Furthermore, they exhibited an increased risk of developing clinical and biochemical features of polycystic ovary syndrome.