Exercise during pregnancy is generally encouraged, not restricted; for most people with an uncomplicated pregnancy, staying active helps manage weight gain, eases aches, and supports better sleep and mood. The commonly cited target is around 150 minutes of moderate activity a week, spread across most days rather than saved for the weekend, though "moderate" is doing a lot of work in that sentence and looks different depending on your fitness level going in. Moderate activity is movement that raises your heart rate and makes you sweat, where you can still talk normally but cannot sing.
Walking, swimming, and stationary cycling are close to universally fine. Modified strength training (bodyweight or light resistance work, adjusted as balance and belly size shift) is generally safe too, with the caveat that after the first trimester, exercises done flat on your back for extended periods are usually best avoided, since the weight of the uterus can compress a major vein and reduce blood flow. Anything with a high fall risk (downhill skiing, horseback riding, contact sports) or a risk of abdominal trauma is worth setting aside for the duration, and activities involving major pressure changes, scuba diving in particular, are a hard no throughout pregnancy.
The signal to stop and check in, rather than push through, is anything that feels like more than expected effort should: vaginal bleeding, dizziness, chest pain, contractions, fluid leaking, or a headache that doesn't ease. None of this is exotic advice; it's the same "listen to your body, stay hydrated, don't overheat" guidance that applies to exercise generally, just with a slightly lower threshold for stopping.
The pelvic floor deserves a specific mention here, because it's doing extra work through pregnancy and generic fitness advice tends to skip past it entirely. It's worth building the same kind of pelvic floor awareness into a pregnancy fitness routine as any other muscle group: a minute of guided practice fits alongside a walk or a swim without needing its own separate plan. Pelvic floor exercises by trimester.
Adjusting as pregnancy goes on
Most people can keep doing what they did before pregnancy, scaled down as the bump grows. Balance changes as your center of gravity moves forward, so activities that rely on quick changes of direction get harder. Ligaments are looser, which makes deep stretching tempting but not always wise; aim for a comfortable range rather than your old limits. Overheating is worth avoiding, so skip hot yoga and hard exercise in very hot, humid weather, drink water, and slow down if you feel hot or breathless.
When exercise isn't advised
Some conditions mean your provider may advise against exercise or limit it: for example certain heart or lung conditions, a cervix that's been flagged as weak or has a stitch (cerclage), placenta previa after 26 weeks, ongoing bleeding, preterm labor, waters that have broken, preeclampsia, or severe anemia. ACOG's guidance lists these in full. If any apply to you, follow your own provider's plan.
Pelvic floor exercises alongside the rest
Pelvic floor training fits into any routine because it needs no equipment and very little time. Starting it early in pregnancy probably lowers the chance of leaking later in pregnancy. Practice both halves: the lift up and in, and a full release, which becomes more important as birth gets closer.