Hi starshaker
Thrush is very common, I don't think a cs is necessary if that is the only reason.
I found this info on ivillage for you:
Candida, a fungal organism, and the most common cause of vaginitis, is more common in women during pregnancy. It has been found that 20 per cent of healthy, non-pregnant women have vaginal candida, and significantly more would have it during pregnancy. Since not all women show symptoms, many no doubt are carrying candida when they give birth. If the baby picked up oral thrush during his birth, he may easily transmit it to his mother through breastfeeding, especially if her nipples have suffered any trauma.
Breastfeeding need not be interrupted if either mother or baby has been diagnosed with a yeast infection. If the mother has nipple or breast candidiasis, or the baby has oral thrush, it is very important for both mother and baby to be treated at the same time. Treatment with anti-fungal medication needs to continue for one to two weeks once the symptoms have cleared. A mother with a yeast infection can give her baby thrush, if she is not careful about hygiene. Thrush is easily transmitted from one family member to another. If a mother has a vaginal yeast infection and is being treated with anti-fungal medication, it is very important that she washes her hands frequently with hot, soapy water, especially after going to the toilet, after nappy changes, and before breastfeeding or pumping. She needs to be on the lookout for any symptoms of nipple thrush, such as suddenly sore nipples once breastfeeding is well established. Also check the baby's mouth regularly for white plaques that cannot be easily removed. If a mother suspects that she or her baby have developed nipple or oral thrush, it is important that they are seen by their GP so that it can be properly treated.
Try not to worry, if you have properly treated your infection you and bub will be fine! I think it recommends continuing to treat the infection even after symptoms clear up.
And if you or bub do get thrush, help is at hand! HTH.