As adjectives the difference between premature and immature is that premature is occurring before a state of readiness or maturity has arrived while immature is not fully formed or developed, unripe, not mature. Those are some differences between a preemie and a full term baby. Although, at age 5, there should cease to be any difference between them. You can permanently use their real age, and forget the corrected age, like i have. Preterm birth is the birth of a baby before the 37th week of pregnancy (3 or more weeks before your due date). The ideal pregnancy is 40 weeks but any birth between 37 and 42 weeks is classed as full term and only those before 37 weeks is classed a preterm or premature birth. Just as all pregnancies are different so are all premature babies. Premature infants can experience a range of medical problems. The lungs are one of the last organ systems to mature and preterm babies might significantly struggle with breathing independently. A very preterm baby also is at risk for bleeding into his brain. Premature birth is the leading cause of death among newborns. Premature babies may have developmental problems or reach milestones later than full-term babies do. In an ideal pregnancy, you give birth once you hit week 40 of your pregnancy, but as many moms can attest, that isnt always the case. According to the center for disease control and prevention (cdc), in 2018, one in 10 babies in the u. While many women are more than ready to be done toward the latter half of pregnancy, the goal always is.