"Hypanus americanus" are ovoviviparous. Mother's bodies protect unborn offspring, while they are developing inside their mother's body. The embryos receive nutrients from the yolk sack early in development. Later in development, however, when the yolk sac is absorbed, the embryos obtain nutrients from the histotroph (the mother's uterine milk). After the "Hypanus americanus" offspring are born, and are outside of the mother's body, parental care ceases. In captivity, gestation lasted 135 to 226 days, after which a litter of two to ten young were born.