Valley Medical Center’s baby boom is a driving force behind finishing two floors in the center’s emergency services tower.

A flow chart is necessary to keep track of how that will happen.

First comes the tower work, then comes the move of 2 West, a surgical recovery wing, to the tower and then comes the expansion of the busy Birth Center into 2 West.

Work on the South Tower, home of the Margarita Prentice Level II Trauma Center, is under way.

The thousands of vehicles driving by every day on South 43rd Street will occasionally see a crane but no actual work, which is happening in the interiors of floors six and seven. The crane will lift materials and equipment to the work area.

The medical center expects to finish work in the South Tower next May, said Todd Thomas, the medical center’s director of facilities. The entire project will cost about $18.4 million.

Design work is under way for the expansion of the Birth Center, where about 4,000 babies are born each year. The center routinely runs at near capacity, or, translated, that means it needs more beds for mom and baby.

The intent is to begin the Birth Center expansion immediately after the 2 West patients move, Thomas said, sometime in the first quarter of 2012. It’s too early to put a cost on the expansion, he said.

The Birth Center and the surgical wing share a wall, so the center will remain one continuous space once the work is done. The old emergency room on the second floor also is being repurposed.