Dong Fan
Did Dong Fan also become pregnant? She surely made a 180-degree turnaround, from planning to divorce Xiao Lu to sharing a rather cozy dinner with him at the very end of the film. The terms of their agreement were: if she got pregnant, she would quit her job as a flight attendant and become a stay-at-home wife and mother. So maybe that's what happened.
From what I gathered, there was an accident involving Dong Fan's plane and, just as she thought she was about to die, she had a vision of HeHe. That might be interpreted to mean that, in return for 'lending' her husband to Mei Zhu in order to save HeHe's life, she would achieve her own heart's desire--to have a baby herself.