The ligaments in your lower back are softened during pregnancy. This means they are more at risk of being damaged which can contribute to lower back pain when high heels are worn.
Flat shoes are your best bet on a daily basis as they minimise strain on your already weakened back but you don’t have to wear them all of the time. A kitten heel is a great alternative to the four inch Christian Louboutins, and pumps are in and work with practically all outfits.
Additionally, boots with low block heel give a balanced and steadied height. Remember though, you probably shouldn’t wear the heels all day, so have a back up flats on standby. If you’re lucky you might even get to wear your sparkly summer (flat) sandals.