Continuity mistake: After the baby is born and Bridget is holding him in her arms, the baby is shown bare headed. After Pamela arrives, the baby is suddenly wearing a hat on his head.
Suggested correction: There could be quite a time lapse before Pamela enters. It is not necessarily the very next second.
Plot hole: When Bridget phones Mr. Darcy, she is told that he has left and is in a taxi on his way home, so Bridget decides to walk to his house where she sees him get out of the taxi and meet his ex-wife at the door, and Bridget thinks they are back together. The problem with this is that she is heavily pregnant and she walks a fair bit across London - hard enough to do at the best of times - and that Mr. Darcy was already in the taxi going home, but she managed to arrive at the same time at his house.
Suggested correction: Mr. Darcy may not have gone straight home. He made have needed the taxi to take him to do an errand, he just doesn't mention this when leaving. Plus, there could have been heavier traffic that we don't see which he could have been stuck in.
Ever gone through traffic in London? During the day it's a nightmare. But in BJ Diary, Mark's mum tells Mark Bridget lives not so far from him, if I'm not mistaken.