Look into the Paleo diet. You lose weight just because of the types of foods you combine. My husband lost 25 pounds quickly!
I agree with @Miyu19, walking helps a lot too. Add more lean meats, fresh veggies and fruits to your meals. And talk to your Dr. about recommending a nutritionists?
Maybe cutting gluten out eating lean meats, healthy fats, fruits, veggies, no sugar. That's just what I eat (sensitive to gluten anyway) and I weight train and swim.
Don't diet. And make sure to talk to your Dr before starting an work out regimes. If you're only overweight, your best bet will be to maintain your weight and to gain about 10 lbs or so during your pregnancy, and if you're obese your Dr may recommend you lose weight. Walking is a great way to ease into exercise, and there are plenty of prenatal workouts on YouTube. Just ask your Dr what's going to be healthiest for you and baby. As far as eating, aim to stick with fresh foods. Shop the perimeter of the grocery store, meal plan and don't be afraid to indulge now and then. With holding cravings is the best way to guarantee a binge
A healthy way to lose weight is to start drink shakeology and try 21 day fix or cize. If you are currently pregnant or just had the baby, it's best to start with the 21 day fix. It's easy, only 30 min a day and you can moderate. I drink my shakeology everyday and it gives me an extra boost of energy and curbs my cravings for junk. You can tell the difference after a month drinking it.