TARTU, Estonia — As Lea Luik waited in a Soviet-era taxi, her husband, Henno, carried their newborns from the nursery. One, then two, then three.

In retellings, the punch line is always the taxi driver’s reaction: “Are you going to empty the whole hospital?”

The sisters Leila, Liina and Lily had been born a month premature. None weighed more than four and a half pounds. For several weeks, home was an intensive care unit. Thirty years later, the sisters are Olympic marathon runners for this tiny Baltic nation — and they are believed to be the first triplets to have qualified for the Winter or Summer Games.

The Trio to Rio, the alliterative sisters call themselves as they prepare to run the women’s marathon in Rio de Janeiro on Aug. 14.