If I were working for any ceo who decided to have a baby, but particularly a woman, I'd want to know about his or her commitment to the business that I'm investing my time, life, and money into. Being a ceo is generally not a 9-5 M-F job, so explaining how you're going to juggle that with the demands of childcare, breastfeeding should you chose to do so, business travel, business needs, etc is fair game when my personal financial results are entangled with the business outcome.
If you're planning on doing what Marissa did and installing a nanny next to your office, great. If you're planning on taking 4 months off for your personal project, I'm going to re-evaluate my dedication to the business if the ceo isn't more dedicated than me.
NB: I currently work for a female ceo; she and her partner have an au pair but he has damaged his career to provide more childcare than her.