How does exercise have a positive effect on the fetus?

Exercising during pregnancy can help you manage your weight gain, reduce your risk of gestational diabetes, reduce discomfort, and make labor and delivery easier. Now, new research shows that sweating, especially after 29 weeks, also has major benefits for the unborn baby.

During pregnancy, exercise can have many benefits for both mother and baby including:
Relieves back pain, constipation, bloating and swelling; Change your mood and increase your energy levels; Help you sleep better; Prevent excessive weight gain; Promotes muscle growth, as well as muscle strength and endurance; Increase your baby's fitness. Exercising pregnant women may have other benefits when following a regular exercise program during pregnancy which may include:
Reduce the risk of gestational diabetes symptoms; Shorten labor; Reduce the risk of cesarean section.

Exercising during pregnancy can help you stay fit and prepare for labor and delivery.
Pregnancy seems like the perfect time to sit and relax. You may feel more tired than usual and your back may ache from carrying the extra weight. But unless you're having complications, sitting still won't do you any good at this point. In fact, pregnancy can be a great time to be active
Before you start an exercise program, make sure you get advice from a therapist and choose activities that are right for you. your actual situation. Although exercise during pregnancy is generally good for both mother and baby, your doctor may advise against exercise if you experience some of the following:
Certain forms of heart and lung disease; Preeclampsia or high blood pressure may form in the first pregnancy; Cervical problems; Persistent vaginal bleeding during the 2nd or 3rd trimester. Exercising during pregnancy may also be unsafe if you have any of the following complications:
Preterm labor; Multiple pregnancies may increase the risk of preterm labor; premature rupture of membranes; Severe anemia.

For most pregnant women, at least 30 minutes of moderate-intensity exercise is recommended on most, if not all, days of the week.
Walking, a great exercise for beginners. Walking provides moderate aerobic conditioning with minimal stress on your joints. Other good options include: Swimming, low-impact aerobics, and stationary bike cycling. Endurance training is fine, as long as you're training with relatively low weights.
Before performing the exercises you need to remember to warm up, stretch and cool down. At the same time, you should drink plenty of water to stay hydrated and be careful not to overheat.
Intense exercise increases oxygen and blood flow to your muscles and out of your uterus. You can continue to chat while exercising. If you can't speak normally during exercise, you're probably trying too hard. Depending on your fitness level, consider the following guidelines:
For a long time you have not done exercise. So, to get you started again, you should start with at least 10 minutes of physical activity each day. Then gradually increase to 15 minutes, 20 minutes, and so on, until you reach at least 30 minutes a day. You used to exercise before you got pregnant. You can continue to exercise to the same extent while you're pregnant, as long as you feel comfortable and don't harm your unborn baby.

If you are unsure whether a particular activity is safe during pregnancy, check with your healthcare provider and you should also consider avoiding:
Any exercise forcing you to lie on your back after the first trimester; Scuba diving, which can put the fetus at risk of decompression sickness; Contact sports, such as ice hockey, football, basketball and volleyball; Activities with a high risk of falling - such as downhill skiing, ice skating, gymnastics and horseback riding; Activities that can cause you to hit the water with great force, such as water skiing, surfing, and diving. Other activities to avoid include:
Exercise at altitude; Activities that can expose you to direct abdominal trauma, such as kickboxing; Hot Yoga or Hot Pilates. If you exercise at high altitude, make sure you know the signs and symptoms of altitude sickness, such as: Headache, fatigue, and nausea. If you experience symptoms of altitude sickness, return to a lower altitude as soon as possible and seek medical attention.

You are more likely to stick with an exercise plan if it involves activities you love and fits into your daily schedule. Consider these simple tips:
Start small: You don't have to join a gym or wear expensive workout clothes to get in shape. Just move. Try a daily walk through your neighborhood or walk around the grocery store a few times. Or take the stairs instead of the elevator. Find a travel companion: Exercising can be more enjoyable if you use the time to chat with a friend. Better yet, join the whole family. Try a class: Many fitness centers and hospitals offer classes, such as prenatal yoga, designed for pregnant women. Choose a class that fits your interests and schedule.

Exercise is equally important, also need to look out for signs of problems. Stop exercising and contact your healthcare provider if you have:
Vaginal bleeding; Dizzy ; Headache; Shortness of breath increases before you start exercising. Chest tightness Other warning signs to look out for include:
Painful uterine contractions that continue after rest; Fluid leaking or spewing from your vagina; calf pain or swelling; Weakness affects balance. Healthy Choices: Regular exercise can help you cope with the physical changes of pregnancy and build stamina for the challenges ahead. If you don't exercise regularly, use pregnancy as an incentive to get started.

References: mayoclinic.org, parents.com