The females, Moja and Savannah, are both 25 years old and both about 20 months along in their pregnancies after mating with the zoo's bull elephant, Jackson.
A blood analysis from the two elephants shows it's 80 percent likely that both calves are females.
The zoo is continuing to draw and analyze blood from both elephants to check for progesterone levels. When the hormone level drops, that means birth is imminent.
The Pittsburgh Zoo plans to increase its elephant herd by using a 724-acre conservation center in Somerset County.
