This is serious stuff today, so let's start with a serious fact: your buttocks adipose tissue (aka fat) plays a very important role in the development of your baby's brain and eyes.

For real. I told you this was serious stuff. But more on that later.

You may know it as your heinie, or maybe your backside. Or your rump, duff, butt, buttocks, bum, cheeks, tush, booty or derrière. Or perhaps one of many un-Pg names that shan't be mentioned here.

It's an area that many mummas say they lose after having a babe or two, or five. I know I did. Mine just disappeared after my first baby. And this was shocking considering my genetic coding has a dedicated booty section. I distinctly recall the morning, I was about four months postnatal, when my husband asked me where it went. It had just vanished! I hadn't even noticed, likely because I was in the thick of new motherhood and checking myself out in a full length mirror was the last place you'd find me. I kindly thanked my husband for pointing out the departure of my rear-end and made a mental note to investigate it's whereabouts at a future date.

There is no medical term for this condition, but I call it Postnatal Flat-ass Syndrome.

Dear mummas, today is all about getting your postnatal bum back. Or maybe if you are lucky, preventing it from ever disappearing.

If you've ever seen me in my office you'll know that I prioritize the glutes right up there with the core. They are crucial for the health of your knees, hips, pelvis and spine. Low back pain will often melt away if you work your glutes alone. Unfortunately, this is a really common area for weakness.

HERE'S HOW TO GET YOUR POSTNATAL BUM BACK MUMMAS:

Step 1: Avoid "mom jeans" at all cost. Granted, bums come in all shapes and sizes (love the bum you're in!), but no bum looks good in "mom jeans" - the high-waisted, bum flattening variety. For some terrible reason these have made a reappearance in recent years. Please spare your bum the humiliation. High waisted is great, but ass pancakeing is not. It's kinda like wearing a bad bra. It's not good for anyone.

Step 2: Work it. This is unavoidable dear mumma. Your bum is mostly muscle, and another fine substance that I'll talk (positively!) about later. Just like all of the muscles in your body post-baby, they have likely lost a little bit of their ummmph. Bring them back to life with some great glute exercises that you can do at home. The fat may be redirected to elsewhere, but the muscles you can maintain.

Here are my favourite glute exercises:

1. CLAMSHELLS

I do this one often when I am just hanging out on the floor with my babes. It's simple and doesn't require too much focus - pretty sure I've done it half-asleep.

Lie on your side, legs stacked, knees bent to about 90 degrees. Lift the top leg off the bottom leg, keeping your feet together. Easy peasy. You should feel this behind your hip, in the deep glutes.

Easier: body weight only
Harder: with an elastic band (make sure you can still move through the full range of motion)
Reps: 10-20 (work to feel it); Sets: 2-3

2. HIP RAISE

This is also pretty straight forward, but requires a little more focus on your core, which makes it a great exercise.

Lie on your back with your feet flat on the floor, hip width apart. Engage your core, squeeze your glutes and lift your pelvis/butt off the floor. Give the glutes and extra little squeeze at the top of the movement. Slowly lower back down, without resting on the floor. Repeat. Try to keep your lower back neutral (small curve), avoid over-arching it by keep your core strong.

Easier: double leg
Harder: double leg with your baby on your pelvis (no photo, but they usually LOVE this!) or single leg
Reps: 15 (double), 10 single; Sets: 2-3

3. REAR FOOT ELEVATED SPLIT SQUAT

Any squat should get those glutes going nicely, but I like a single leg, rear foot elevated one. Watch that your front knee doesn't wobble inwards - keep it in line with your toes. Focus on squeezing the glutes when you are going back up. Keep the core strong!

Easier: shallow squat (1/4 way)
Harder: deep squat (half to full way)
Reps: 10-15 each side; Sets: 2-3

4. HYDRANTS

This one also requires some focus - really watch that your spine and pelvis stay neutral (square), trying to minimize any tilting or lateral shifting. Do this by engaging your core. Imagine a hot cup of coffee on your back (please don't actually do this *eye roll*).

You should feel this in your supporting glutes (if you are keeping good alignment!), as well as the rotating/moving leg. Respect your hip range of motion or else your pelvis will shift too much.

Easier: little dogs
Harder: big dogs
Reps: 10-15; Sets: 2-3

5. PULSES

This is another really simple and quick exercise, perfect when you only have a minute - like in between the 9th and 10th reading of the moo baaa lalala book.

Hold a good, stable table position (don't let the lower spine arch/extend beyond neutral here) with a strong core, while moving the bent leg up and down through a small range of motion. Keep the raised foot parallel to the ground and imagine stomping the ceiling. Squeeeeeze your glutes.

Reps: work to a burn, then add 10 more
Sets: likely only one because you'll have to read that damn book again

So you may be wondering about that bum baby brain fact that I mentioned earlier: where does the disappearing bum fat go?

Well, apparently Postnatal Flatass Syndrome has some scientific backing. Of course, muscle loss during pregnancy and postpartum are not uncommon as many women reduce their activity levels, but apparently there is more to the bum vanishing then just that.

Your gluteofemoral fat (bum and thigh fat) stores omega-3 fatty acids. When you are pregnant, your body hoards DHA (the brain building omega-3) in your butt and thigh fat. This is where it likes to hang out. This DHA is then passed to your babe during high-rate brain and eye development periods - in the third trimester, and to your little newbie via your breast milk.

Essentially, your bum fat nourishes your baby's brain during these crucial periods of development.

This might explain a bigger bum in the first phase of pregnancy (storing it up), and the seemingly rapid shrinkage of it in the third trimester and the first few months after delivery, as these fat stores are mobilized to fuel your baby's brain.

So there you go. At least it all went to a good cause!

How can this highly scientific knowledge help you (and your bum)? Many mummas focus on getting proper nutrients in during pregnancy, but we tend to let the healthy eating slide once the babe arrives. Being lax with your diet postpartum may mean less omega-3s going in, which might mean more bum fat being used up for baby's needs.

Weird, but true. All to say, keep the omega-3s going postpartum!

Wild fish (salmon, tuna, mackerel) is the most plentiful source of DHA. Pregnant and lactating women are often advised against eating too much fish due to mercury levels, but most health professionals recommend fish twice a week to meet your DHA recommended amounts. If you aren't a fish eater, consider a high-quality fish oil, but consult with your doctor before taking any supplements. Flax oil, walnuts, chia and hemp seeds are also good sources of omega-3, but fairly large quantities have to be eaten to meet the daily requirements, since your body has to convert these fatty acids into DHA. If you're not sure if you're getting enough omega-3 in your diet, talk to a registered nutritionist, your doctor/midwife or a naturopath.

Take home message: Eat well. Get your omega-3s in. Work your butt muscles.

And avoid flatassening jeans.