Their relationship would likely deepen. The impending arrival of a baby would bring them closer together on an emotional level. They'd have to communicate more about their hopes and fears for their family. For instance, they might have long talks about what kind of values they want to instill in their child.
In fanfiction, Gamora and Peter Quill's romance is often depicted as a complex and passionate relationship. Their different backgrounds, with Gamora being from a tough and war - like upbringing and Peter having his own Earth - influenced charm, create an interesting dynamic. Writers often explore how they overcome their differences and grow closer through shared adventures and mutual understanding.
Gamora is the last of her species. She was raised by Thanos. Thanos took her from her home planet when she was young. He trained her to be a deadly assassin.
One key element is the destruction of her home planet which left her alone. Then Thanos coming into her life and making her his protégé is crucial. Also, the training she received from Thanos which made her a force to be reckoned with in combat is an important part of her origin story.
The key elements are her origin from the Zen - Whoberi, Thanos killing half of her people and adopting her, and her transformation from being Thanos' assassin to a hero.
Another plot could involve them preparing for the arrival of the baby. They could be seen shopping for baby supplies in different alien markets. Quill would be clueless about most things, while Gamora has a more practical approach, leading to some comical situations.