Look, eating anything in excess is bad, okay? Lychees are totally fine in moderation, just wash them thoroughly to remove chemicals. Don't listen to random people telling you to avoid every fruit.
Yes, you can have a few lychees, but don't eat too many at once because they are very sweet. I had a C-section and was told to eat a balanced diet during pregnancy for smooth recovery later. Just wash them properly before eating.
Listen to me, don't worry so much about every little fruit. Lychees are fine and give you good vitamin C, but they can spike sugar if you eat too many. Have a few as a treat, wash them well, and stay happy.