I should firstly congratulate you. The process of conception through to bringing a child into this world is such a fascinating process - there are so many things that need to happen to create a healthy newborn. With this in mind, there are a few things your body will go through that you might not have expected. A lot of the changes that happen to your skeleton are reversible if you know what to do. I'll firstly run through a few of the key things to keep in mind whenever you're starting to exercise or strengthen after pregnancy and make some recommendations about where to start.
First of all, lets run through the harder parts of pregnancy. Humans have evolved to have larger brains than any other animal on the planet. What this means is that our heads have also needed to expand. When you compare a new born human with any other animal on the planet, they're very behind on milestones. Humans sleep up to 16 hours of the day and can take up to 18 months to start walking which is a stark difference to other mammals who can run away from predators from day one. Our bigger brains have been great for a multitude of reasons but we do pay a price. If you look at the pelvis to head ratio for humans compared with other animals you can understand how childbirth can come with some difficulties. It's not uncommon to experience pelvic floor tearing and trauma through a natural childbirth which can create a weakness or loss of elasticity (which the body will need to compensate for). The good news to this is you're often able to strengthen the pelvic floor or learn ways to adapt for the long term.
Secondly, whereas other animals generally walk on four legs, we walk on two. The 'core' system is made up of the ribcage, diaphragm, pelvis and abdominal wall. Our core muscles work a lot better on four legs than two (this is why a lot of core strengthening exercises happen to be on your hands and knees). Read this blog to understand a bit more about this. Pregnancy essentially affects your core muscles is in a multitude of ways:
There are changes in centre of mass (from having more weight in the tummy) often results in a flexed lower ribcage. This can create a loss of flexibility which changes how the diaphragm and abdominals control the pelvis.
A natural birth can create a weakness in the pelvic floor muscles.
A caesarean section can create a loss of stabilisation in the deep abdominals.
A hormone called 'relaxin' creates looser ligaments in the pelvis to prepare you for childbirth. It can take up to 12 months for this to normalise after childbirth.
There's a lot you can start doing within reason, just remember that slow and steady wins the race. Try to remember that your body likely won't handle big increases in load and intensity so don't lose your patience. Here's a few thing to remember as you start:
1. DO: Low intensity exercise, walking, cycling and water exercise.
DON'T DO: High intensity exercise or jumping.
Low intensity exercise can include a number of things. Yoga, Pilates, gentle water exercises and walking can all be great places to start. The reason is that low intensity exercise doesn't place a lot of stress through the abdominals and pelvis. It takes about 12 weeks to start moderate intensity exercise like jogging and even longer to get into high intensity exercises like lifting weights.
2. DO: Extension based exercise and exercises on your hands and knees/tummy.
DON'T DO: Abdominal crunches and exercises on your back for 12 weeks.
There's a couple of reasons to avoid crunches and anything flexion based (when the torso comes forward) for 12 weeks. The spine becomes flexed from pregnancy due to growing a baby in the uterus, carrying children following birth as well as an increase in slumping when breastfeeding. So if you encourage this type of movement through exercise, you're strengthening a dysfunctional movement pattern. This can put downward pressure through the pelvic floor and increase the risk of a uterine, umbilical or inguinal hernia. Early exercises should encourage a neutral spine and focus on abdominal and pelvis strength training. In addition to this, the ligaments around the pelvis are looser so the pelvis has less passive support. The ligaments of the pelvis are on stretch when you lie on your back so exercises on your back can cause a lot of unwanted movement compensation. This includes things like bridges, dead bugs, toe taps etc. You're much better starting off with exercises where gravity assists your pelvis. This acts to assist the pelvic floor while also making it easier for your abdominals and torso. This includes to be exercises on tummy, hands and knees or even on your side.
3. DO: Exercises that challenge your abdominal wall with a neutral spine and/or learn to use your inner abdominals with real time ultrasound.
DON'T DO: Don't get into the habit of tightening your tummy to get your core strong.
Often after childbirth, people can get in the habit of gripping their external abdominals. Whether they're told to do this from a friend, personal trainer or 'core' coach, a lot of what people think about the core muscles is misinformed. If you'd like to know more about this read this blog. Core strengthening is often complex and multifaceted and people have tried to simplify it to make money. What often happens is improper exercises will do more harm than good by creating layers of compensation. Our bodies are smarter than we give them credit for. More often than not, if you do gentle, graded abdominal exercises with good movement and body positioning (keeping in mind the points I've made above) then you'll get robust and resilient naturally. This often comes down to working with someone who looks at the body as a being interconnected rather than just looking at the abdominal muscles as a separate system.
What I will tell you is that no two people going through this are the same. Everyone has had their own lives, injuries, careers and hobbies before having children so if you're trying to rely on a 'one size fits all' like an online course or a book then you might run into trouble. Of course, in saying all this if you had no trouble with childbirth, no previous pain or injuries and were previously fit and healthy there's a good chance you'll have no problems adapting around the natural changes of pregnancy.