Good self-care helps keep your immunity strong. Eat nutritious foods and drink lots of water to stay hydrated. Make sure you’re taking your prenatal vitamin daily. If you feel rundown or think you’ve caught a cold, the best natural methods to boost your defenses are vitamin C and zinc, and as much rest as possible, advises Shirazian. Get a good night’s sleep, or take naps when you can, if you find it difficult to sleep at night.