As previously reported, O'Hara, who received a Tony nomination for her portrayal of Ensign Nellie Forbush, will depart the production March 7 in anticipation of the birth of her first child.
O'Hara, it has also been announced, will return to the Tony-winning revival of South Pacific on Oct. 6.
Laura Osnes made her Broadway debut as Sandy in the 2007 revival of Grease following a talent search on the reality-television competition "Grease: You're The One That I Want." She was also recently seen in the Kennedy Center's Broadway: Three Generations concerts.
Tony winner Bartlett Sher directed the Tony-winning South Pacific revival.
Tickets for the Lincoln Center Theater revival of South Pacific are available at the Vivian Beaumont box office (150 West 65th Street), at Telecharge.com or by visiting www.lct.org.