According to Noonan, there are five big mistakes women often make when approaching fitness as a new mom. The first is the most dangerous: starting too soon. "Give your body time to heal and ensure you have had your 6 week check up before starting any exercise routine," she writes, conceding, however, that it could take longer. It's most important that women slow down and listen to their body, because ignoring those signs could lead to real problems. "Don't over do it," she writes. "This will cause so much muscle tension and tightness you won't be able [to] sit on the toilet [or] bend down to pick up the baby and will turn you off going back." When you are finally ready to ease in, Noonan says, there are some exercises you definitely want to avoid: sit-ups and crunches, which aren't a great idea when you're pregnant, either. That's because working your rectus abdominis muscle (aka your "six-pack" muscle) during pregnancy can increase your risk for abdominal separation, and can make it harder to heal after you give birth. "This applies to every pregnant woman, the first 6 months PP [postpartum] for everyone and for any one with any abdominal separation until it heals," Noonan writes. "Other abdominal exercises to avoid include — leg lifts, mountain climbers, chin-ups, jack-knives or any abdominal exercise that feels uncomfortable or causes a bulge to pop through." While a safe and smart fitness routine can be a great way to help a new parent's body recover its strength after delivery, the bottom line is to always check with your doctor — when and how you can exercise after giving birth can vary from person to person.