AMAG Pharmaceuticals Inc. is buying the stem-cell storage company Cord Blood Registry for $700 million from private equity firm GTCR.

Waltham, Massachusetts-based AMAG focuses on specialty drugs for maternal health and anemia. Its products include Makena, which helps reduce the risk of preterm birth. Cord Blood Registry provides services which allow for the preservation of a child's umbilical cord blood stem cells and cord tissue samples for potential future medical use.

AMAG said the acquisition would expand its suite of maternal health offerings. Cord Blood Registry had revenue of about $126 million in 2014, the company said.

Newborn stem cells have been used for more than 20 years in patients with over 80 serious diseases, including congenital diseases and those that present in childhood, AMAG said.