T R5.35. Twin births In 2000, the Journal of the American Medical Association published a study that examined a sample of pregnancies that resulted in the birth of twins. Births were classified as preterm with intervention (induced labor or ce- sarean), preterm without such procedures, or term or post- term. Researchers also classified the pregnancies by the level of prenatal medical care the mother received (inade- quate, adequate, or intensive). The data, from the years 1995-1997, are summarized in the table below. Figures are in thousands of births. (JAMA 284 [2000]: 335-341) Twin Births, 1995-1997 (in thousands) Preterm Preterm (induced or (without Term or cesarean) procedures) Postterm Total Intensive 18 15 28 61 Care Level of Prenatal Adequate 46 43 65 154 Inadequate 12 13 38 63 Total 76 71 131 278 Is there evidence of an association between the duration of the pregnancy and the level of care received by the mother