Then I don’t think it works. Bellatrix’s pregnancy can work during book six, since she was absent for the entire book, but she showed up regularly throughout book seven.

Please take into account the second someone becomes pregnant that they don’t magically gain a beach ball under their shirt.

If Bellatrix became pregnant very late June or sometime in July than she’d be less than 3 months pregnant for her two appearances in the summer, and then by the time of her next appearance in Malfoy Manor she’d have already given birth a month previous.

Timeline definitely works.

I guess she could be a new mom by the time of Malfoy Manor. Its just hard to imagine her not mentioning to everyone within earshot that she has just become the mother of Voldemort’s child.

1. Because she is the "Cursed Child"

2. I make her overthrow Voldy, become the new main villain, and become the true Dark Lord herself (possibly fighting Snape over which one gets to be the Dark Lord) and then I would add Rayvena to the book and have them get married, that way not only can Bellatrix actually love someone romantically of her choice, but she would also be a far better villain than Voldy.

3. He probably didn't, it was most likely Bellatrix who love potioned Voldy and was the one who wanted a child possibly to raise her to kill Harry and all the "Mudbloods" or smth.

If Bellatrix had tried to give Voldemort a love potion, she would have been quickly murdered.

Who said she'd offer it to his face? She could've easily dropped it in his drink while he wasn't looking.

Voldemort would know. He doesn’t typically feel love or infatuation , so he would recognize if he was feeling atypical. Even if he was too infatuated to notice at the time, he would figure it out once it wore off.

That is a valid statement, I'll give you that, but why would he willingly want to have a child with Bellatrix?

It doesn’t make sense. I gave my theory earlier in the thread. It’s a stretch, but I think it works better than any other theory.

Resurrection plan. Voldemort needed the bone of his father to resurrect himself in GofF but it could be any blood relative and Wormtail and Voldemort chose Tom Riddle Senior out of convenience but what if it could be any blood relative. A daughter would count then. Also, the daughter could be trained into a loyal servant, maybe the most loyal of all who would give her right hand to resurrect her father, as well as maybe a vessel for his soul to posses . I think Delphini was conceived as a failsafe.