First, please know that this is more common than you think. Many great CEOs are women who were pregnant and had kids during their tenure -- including Marissa Meyer who had 2 kids while CEO of Yahoo. In general, and all other matters that might have sensitivity -- is to take ownership of it and be proactive in presenting a plan. Investors usually have a much bigger issue if you obfuscate or shield them from the truth.
You can also get advice from others who've been down this path. Rachel Chalmers, a former female VC and mother, has office hours on Friday for advice.