Scary. Like aliens. That is how Kerry Mastera remembers her twins, Max and Wes, in the traumatic days after they were born nine weeks early. Machines forced air into the infants’ lungs, pushing their tiny chests up and down in artificial heaves. Tubes delivered nourishment. They were so small her husband’s wedding band fit around an entire baby foot.

Having a family had been an elusive goal for Jeff and Kerry Mastera, a blur of more than two years, dozens of doctor visits and four tries with a procedure called intrauterine insemination, all failures. In one year, the Masteras spent 23 percent of their income on fertility treatments.

The couple had nearly given up, but last year they decided to try once more, this time through in-vitro fertilization. Pregnancy quickly followed, as did the Mastera boys, who arrived at the Swedish Medical Center in Denver on Feb. 16 at 3 pounds, 1 ounce apiece. Kept alive in a neonatal intensive care unit, Max remained in the hospital 43 days; Wes came home in 51.

By the time it was over, medical bills for the boys exceeded $1.2 million.

Eight months later, the extraordinary effort seems worth it to the Masteras, who live in Aurora, Colo. The babies are thriving and developing their own personalities  Wes, the noisy and demanding; Max, the quiet and serious. Like many other twins conceived through in-vitro fertilization, the Mastera boys will go down in the record books as a success  both for the fertility clinic that helped create them and the neonatologists who nursed them to health.