The bizarre phenomenon is actually well-known among mothers, who all experience the growth throughout the day.
According to birth doula Susannah Birch, ab muscles also play a role.
Birch told Trimester Talk, "At night time, your abdominal muscles are tired from holding your bump [and they] loosen as they grow more tired, which allows your bump to sit out further and appear larger."
"When you go to sleep, your muscles get a chance to rest and recuperate so they're refreshed and ready to maintain your bump's position when you wake."
Everybody's muscles adapt throughout the night-day cycle of the time zone you live in.
Your muscles relax in the evening, recuperating so they can be strong and responsive during your active hours.
Meghan's sudden growth could also be due to her experiencing "the pop."
Amanda Kallen, MD, assistant professor in the division of reproductive endocrinology and infertility at the Yale School of Medicine, told Women's Health that this has to do with the uterus expanding above the pubic bone.
"At this point, you may start to feel—and even see—your pregnant belly pop because it's no longer hiding behind the bony pelvis," Dr Kallen said.