During baby's organ formation (first 4 months) one should make every effort to prevent toxins and chemicals from entering mothers body. The food she eats, the water she drinks and the air she breathes should be as clean as possible. Better to use mosquito net at night and mesh on windows to avoid mosquitoes. Keep the surroundings dry to prevent mosquito breeding. Rooms well lit from sunshine will also drive away mosquitoes. If it's hot, use a ceiling fan.