I would assume they relax and stretch along with the uterus, since the uterus is a muscle as well. In certain cases though you can have a diastasis recti which is when the most outer layer of muscle splits in the middle and this can cause what looks like a valley in the abs later on after baby is born.
The Eastern Time (ET) or Eastern Standard Time (EST) is also known as North American Eastern Standard Time. It is the time zone that pertains to the east coast of North America. The clock time in the Eastern Time is based on the mean solar time of the 75th meridian west of the Greenwich Observatory in London.
What does it refer to? The Eastern Standard Time, abbreviated EST, refers to the standard time on the 5th time zone west of the Greenwich Meridian. This time zone is reckoned 75 degrees west of the Greenwich and it encompasses most of the eastern parts of the United States. It is also the timezone used in Canada, the Caribbean, and in a few countries of South America. All places using it are five hours before the universal time, UTC-05:00.