One common theme could be the protection of the pregnant character. The growls might signify the male character's determination to safeguard the pregnant female. Another theme could be the anticipation of new life in a rather unique, often fantasy - based setting.
In some cases, the stomach growl might be part of a magical or cursed situation. Maybe a character has been cursed so that their stomach growls at inopportune times, causing trouble or embarrassment. Or it could be a side - effect of some supernatural power they've acquired. This can add an interesting twist to the story and explore how the characters deal with this strange new development within the framework of the Supernatural series.
One common theme could be hunger and the search for food. Since the stomach growl indicates hunger, the fanfic might focus on ponies trying to find something to eat in their magical world.
One common theme is survival. Since 'The 100' is set in a harsh world, the pregnancy adds another layer of challenge. The characters have to ensure the survival of the mother and the unborn child in a world full of danger.
I'm not sure specifically which 'pregnant growl fanfiction' is good. You could try searching on popular fanfiction websites like Archive of Our Own. There might be some stories related to werewolves (which could involve growls) and pregnancy themes in their vast collections.
Love and support are common themes. Usually, Bella's relationship with Edward or other important characters deepens as they support her through the pregnancy.
Another theme is the relationship changes. Her relationship with the baby's father might be explored, whether it's a new relationship or an existing one. There could also be changes in her friendships as she focuses more on her upcoming motherhood.
Family support is also a big theme. It shows how their friends and family react to the news, whether it's with joy, concern, or a mix of both. In some garmau pregnant fanfiction, the family members play an important role in helping the couple prepare for the baby.
One common theme could be the relationship changes. With the pregnancy, the characters' dynamics might shift in many ways.
One common theme could be the challenges of pregnancy. Since Undyne is a strong character, it might be interesting to see how she copes with the physical and emotional changes that come with pregnancy. Another theme could be the relationship between Undyne and her partner during this time, like how they support each other.
One common theme might be the anticipation and excitement within the family and the community. Since Neytiri is an important character in the Avatar universe, her pregnancy would likely have a big impact on those around her.