This article quotes several parts of an article by Ceridwen Morris and posted on Yahoo.com
What a picture of a fairytale story come true! We all rejoiced in the birth of the first prince of this century with pictures of "a beautiful, healthy baby, a doting, proud father, and a glowing, serene mother. But wait! Look closely. When Kate passes the swaddled heir to her charming William, she reveals a real-life new mom belly. Round as a six month pregnancy. Clear as day."
What's up with that?
"Can anyone tell me why Kate's stomach still looks pregnant after the baby isn't inside her anymore? I had no idea that happened … Is it fluid or something?"
"Women are often surprised to learn that looking very pregnant is not only normal for the first few hours or days after giving birth but for weeks or more. Women have 40-50% more blood volume during pregnancy; all that excess fluid doesn't go down overnight. Also, the uterus must shrink back down to a fraction of the size it was during pregnancy. But it can take about a month or so."
Studies have shown that compression helps to heal wounds faster, even post baby-bod bellies, but it has to be the correct amount of compression. To facilitate healing there should be enough elastic in the garment to compress the belly without pressing so hard that the garment takes over the work of the abdominal muscles.
Many of you may have seen articles written about celebrities who claim wearing very tight abdominal binders for a few months helped them to develop a flat tummy after childbirth. Nothing could be further from the truth!
As a physical therapist who specializes in treating postpartum women, I would like to give a warning that tight abdominal binders will not help to flatten your tummy; and using an abdominal binder actually weakens stomach muscles. Another problem with abdominal binders is that they create compressive downward forces which push internal organs down towards the worn out muscles at the bottom of the pelvis (pelvic floor muscles). This can lead to problems such as chronic urinary leakage and pelvic organ prolapse.
The answer to how to help heal and flatten your post baby bod tummy is to wear a compressive garment that will help to encourage your abdominal and pelvic floor muscles to contract and to hold your organs "up and in". So, you need to wear a garment that will offer compressive support at the bottom of your pelvis and your tummy. As I mentioned before, you need to use just the right amount of compression. “Shape wear" under garments, the ones we see advertised all over the internet, are too tight and can weaken the abdominal muscles. To date, I am not aware of a garment available on the market that I can recommend. So, for now, try using a sports top, like a yoga top, and underpants with enough elastic to give your pelvic floor support.