Society or the community they live in could also act as antagonists. If they live in a judgmental community that looks down on unmarried couples having a baby, they could face a lot of ostracism and negative comments. This would make their journey through the pregnancy even more difficult.
It could be an ex - partner of either Leah or Jasper. For instance, if Jasper has an ex - girlfriend who is jealous of Leah and the new baby, she might try to cause trouble between them. Maybe she spreads false rumors about Leah to make Jasper doubt her.
Their families could potentially be antagonists in a sense. If their families have different values or expectations, they could create conflict. For example, if Jasper's family is very traditional and doesn't approve of Leah because she's from a different background and now she's pregnant, they could put a lot of pressure on the couple.
The Capitol could still be the main antagonists. They might see Katniss's pregnancy as a threat, either because they fear the child could grow up to be a symbol of resistance like Katniss or just because they want to maintain control over her. They could try to harm her or the baby in some way.
In some cases, there could be a rogue vampire with a vendetta against the Cullen family. This vampire might target Alice and Jasper specifically because of their unique abilities and importance within the family. They could try to disrupt their relationship or harm them in other ways.
In some Bella and Jasper military fanfictions, the main antagonists could be rival military groups. These groups might have different ideologies or goals and be in direct competition or conflict with Bella and Jasper's unit. For example, they could be fighting over territory or resources. Another type of antagonist could be a power - hungry military leader within their own ranks who is willing to sacrifice the well - being of the soldiers for personal gain.
Often, the Volturi can be antagonists. They might not approve of Jasper and Bella's relationship for some reason, like they think it goes against vampire laws or traditions. Another possible antagonist could be a rogue vampire who has a vendetta against the Cullens and sees Jasper and Bella's relationship as a way to get to them.
It could be a group of mean girls in their school who are jealous of Bella and Leah's friendship. They try to spread rumors about them, like saying that Leah is only using Bella to get good grades or that Bella is trying to steal Leah's popularity. But Bella and Leah are smart enough to see through their lies and stand up to them together.
The main antagonists could be some of the more traditional pure - blood families who look down on Ron and Luna's relationship. They might see Luna as an oddity and Ron as not being from a high - enough status family. They could try to interfere with the pregnancy, either by spreading false rumors or trying to separate the couple.
It could be the traditional enemies from Naruto's world, like the Akatsuki. They might see the union of Naruto and Rias and their unborn child as a threat to their plans for world domination. They could try to kidnap Rias to use her as a bargaining chip against Naruto or to study the unique nature of their child.
The old enemies of Percy and Annabeth like the Titans or some of the more vengeful monsters could be the main antagonists. They might see the unborn child as a threat or an opportunity to get back at Percy and Annabeth.
Their friends could also be antagonists in a sense. For example, if there's a friend who has always had a crush on Freddie and is jealous of Sam. This friend could spread rumors about Sam being a bad influence or try to convince Freddie that he's making a huge mistake by staying with Sam and having a baby. Another scenario could be that their friends don't take the situation seriously and keep pressuring them to act like they used to, which makes it hard for Freddie and Sam to focus on the pregnancy.
It could be the jealous servants in the Beast's castle. They might not like Casey in the first place, and her pregnancy could make them fear that she will gain even more power and influence. So, they could try to sabotage her pregnancy in secret ways.