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:
EDIT: Found another example where a daughter emerged from the Yagna instead of a son even though the original intention was to get a male heir. The Devi Bhagwat Puran Book 6, Chapter 21 mentions the story of Ekavali born as a result of a Putrakameshthi Yagna by a king called Rabhya:
When the queen thus spoke very distressedly, the king called the Brāhmaṇas, versed in the Vedas, and began to perform an excellent sacrificial ceremony, in due accordance with the Vedic rules. With a desire to get a son, he made many presents in profuse quantities. When copious quantities of ghee were offered as oblations, there arose, from the fire, a girl beautiful in all respects and endowed with all auspicious signs.........When the girl arose from the fire, the priest (Hotā) took that lean and thin lady of a nice waist by her arms and presented her to the King and said :-- O King! Accept this daughter, endowed with all auspicious signs. When Homa was being performed, the daughter came up like the garland Ekāvalī; therefore this girl became famous in this world by the name Ekāvalī. O Ruler of the earth! Take this girl, resembling a son and be happy.
O King! Viṣṇu, the Deva of the Devas, has given you this Jewel, this daughter; so be contented. Hearing thus the words of the priest, the King saw this good-looking girl and with gladdened heart took the beautiful daughter from his hands.
Thus with that lovely daughter he went to his wife Rukmarekhā and said :-- O Beautiful One! Take this daughter. The queen Rukmarekhā felt the pleasure of having a son when she got in her arms that lotus eyed beautiful daughter.
The King next performed the natal and other ceremonies of the daughter and did all other acts as if she had been a son to him duly in accordance with the rules. The King performed his own sacrificial ceremonies and gave away lots of Dakṣiṇās to the Brāhmins and dismissed them and became very glad. That beautiful girl was nursed and cared after like a son and she grew older day by day.
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.