What happens on Mustafar, stays on Mustafar
Before Obi-Wan tells Padmé of Anakin’s fall, the embattled Jedi Knight reveals to his wife that he is being sent to the Mustafar system. Now, the heavily pregnant senator had an idea of where her husband was going but didn’t know why.
When Kenobi shows up and asks when the last time she saw Anakin was, she tries to lie but Obi-Wan is quick to call her out. He then reveals why he needs to find his former student which Padmé deduces is to kill him. He then questions if Skywalker is the father of her unborn child. When Padmé doesn’t respond, he knows what the answer is before he leaves to confront the man he once considered to be his brother.
Amidala, knowing she has to do something and to bring her husband back to light, journeys to Mustafar, despite Captain Typho’s objections. Unbeknownst to her, Obi-Wan had hidden away on her ship which is later seen as a betrayal by an unhinged and dangerous Anakin.
While it’s not made clear, during the flight to Mustafar, Padmé has time to reflect on what she should say. She knows she wants to take her husband and their child to someplace that is safe and away from the Republic. However, when she tries to convince Anakin of this, he says he is more powerful than Palpatine and has the power to overthrow him.
What makes the situation even more complicated is the appearance of Obi-Wan on the ship’s ramp. This sends Anakin into a massive fury and he uses the Force to choke his wife into unconsciousness, which prompts her to go into premature labor.