Pregnant Jessica Simpson 'doing great'

Jessica Simpson is "doing great" with her pregnancy.

The 'I Wanna Love You Forever' star - who is expecting her third child with her husband Eric Johnson - has been documenting her tough pregnancy online and Jessica's sister Ashlee has revealed she is doing "great".

Speaking to Entertainment Tonight, she said: "She's doing good. She's doing great."

And in another interview with Extra, she added: "She's ready for that baby."

Meanwhile, Jessica - who also has Maxwell, six, and Ace, five - previously admitted he "doesn't understand" how she got pregnant again.

She admitted: "I thought about [having another baby], but I didn't really know that it could actually happen. We definitely always love to practice. We actually weren't practicing very much that month so I don't understand. We try [to figure it out]. This might be a miracle baby."

And Jessica's children are "so excited" to be a big brother and big sister.

She added: "They're so excited because they're only fourteen months apart, so they didn't get to experience the excitement of each other. But when I told them that we're having another baby, I know that they'll remember that for the rest of their lives. They are most excited about learning how to do the swaddle. Maxwell, my daughter is just so happy that it's a girl. They ask me the craziest questions that I can't say on TV ... 'How does the baby come out?' 'Where does the milk come from, I don't understand!' I'm a little bit too honest, and Eric's like, 'I don't think we need to give out ALL the information, Jessica. So, I'm scaring my kids, I think."