arriving, existing, happening, or done too early, before the intended, proper, or usual time;
e.g. Because of their premature arrival, we had not finished making all the necessary arrangements.
(adjective)
born before the full gestation period, especially at or before 37 weeks, often leading to complications, used to describe the timing of a baby's birth;
e.g. She went into labor a month early and gave birth to a premature baby.