The first thing to remember is to always consult your healthcare professional first about what types of exercises you want to do while you’re pregnant. You should never perform exercises that involve being supine (laying on your back) when you’re pregnant. Also avoid any activities that increase your risk of falling, especially on your belly (such as box jumps and pull-ups).
If you already have experience lifting weights, you probably can continue to strength train as long as you understand your body and the changes that are happening to it. For example, pregnancy changes your overall body mass and center of mass, as well as your spinal curvature, which could cause spinal instability. Changes in balance and increased flexibility around joints are side effects of being pregnant that can affect your normal resistance-training routine. As long as you’re careful and listen to your body, weightlifting during your pregnancy can provide the same benefits it does when you’re not pregnant.
Finally, many doctors encourage their patients to hold off weightlifting until after they’re 12 weeks along in the pregnancy. However, talk to your doctor about your workout goals and your pregnancy to find out what’s right for you.