It’s not like your baby will notice whether you wear expensive unmentionables from Victoria’s Secret or cheap tight whities from Target. Instead, it’s the breathability that matters. When you become pregnant, you’ll notice an increase in the amount of vaginal discharge you have. The hormones your body produces will cause an imbalance in your vagina’s natural bacteria, so secretions will increase and you’ll be at a higher risk for a yeast infection. If you don’t wear breathable, cotton underwear during your pregnancy, that risk will be much greater. Though a yeast infection won’t directly harm your baby while he or she is still in utero, your pregnancy will make treatment more complicated. You won’t be able to use the usual medications recommended because they can harm your baby. Also, if you have a yeast infection when you give birth, your baby might take on an infection resulting in thrush. This is treatable, but it’s definitely an added complication that’s best to prevent in the first place.
Keeping yourself clean and dry is the best way to prevent a yeast infection, but avoiding thongs and silk underwear is another excellent solution. Anything but cotton panties will hold too much moisture and become a breeding ground for bacteria. For the duration of your pregnancy, only wear what you might otherwise consider “granny panties” to keep your genital area clean and dry. By saving the sexy underwear for your post-delivery outfits, you’ll prevent one of the most common infections during pregnancy, which will make those nine months a lot less stressful and easier on your body.
Source: Barbara Jo McGarry: Vaginal Discharge. Primary Care Procedures in Women’s Health pp. 79-94 2010