Besides the famous Putrakameshthi of Ramayan, there are other examples as well in the scriptures and every time it has resulted in the birth of sons.
Mahabharat Book 13 Anushasan Parva Section XXX mentions Rishi Bharadwaj performing a similar Yagnya for Divodas:
"Bhishma continued, 'Unto him who pleaded so piteously, Bharadwaja of great energy said, Do not fear! Do not fear! O son of Sudeva, let thy fears be dispelled. I shall perform a sacrifice, O monarch, in order that thou mayst have a son through whom thou shalt be able to smite thousands upon thousands of Vitahavya's party. After this, the Rishi performed a sacrifice with the object of bestowing a son on Divodasa. As the result thereof, unto Divodasa was born a son named Pratarddana.
(BTW Mahabharat also talks about Bharadwaj rishi beng involved in another Yagnya of this kind, the Marut-stoma where King Bharat receives a son.)
Again in the 26th Chapter of the Sahyadrikhanda of the Skanda Purana we come across the following:
Some may doubt that it could be the translator's bias but further verses give us direct proof:
In yet another example from the same book we see:
Again in the legend of Devi Meenakshi's birth, her king Malaydhwaj was advised by Indra to conduct a Putrakameshti for an heir:
This resulted in the emergence of a three-year old girl from the Yagnya Vedi but Malaydhwaj was disappointed since he was expecting a male heir:
Judging by these examples I would say that the Putrakmeshthi Yagnya was conducted specifically for obtaining Putra not Putri which kind of makes sense since all these kings were looking for heirs for their kingdoms.