Most women will experience increased breast size during pregnancy and breastfeeding. The size change will vary from woman to woman, but generally it will increase at least one bra and one cup size (for example, an average woman's normal size 36B will increase to 38C). However, there are those of us who can truly go from a 34B to a 40DD too. Expanding ribcage to accommodate growing baby and beginning of milk production are responsible for this change. We recommend measuring yourself before purchasing new lingerie during this exciting time of your life. Please note that, for hygenic reasons, returns are not accepted.