Your breasts and ribcage will begin noticeable expansion. You might invest in 1–2 transitional nursing bras now, but ensure they have room to grow.
Your ribcage naturally widens during pregnancy; if the band digs in even on the loosest hook, you need to size up. Shopping and Sizing Tips
Red marks on your shoulders or torso, or underwire pinching breast tissue.
Most women find that their bra needs evolve throughout their pregnancy and nursing journey:
Do not wait for a specific week if you experience these indicators of a poor fit: