Two weeks before you return to work, rent an efficient and comfortable breast pump and start building up a supply of frozen milk. If the day you are to return to work arrives, and you don't have a freezer full of breast milk, one bottle of formula fed to your baby is not the end of the world. After returning to work, express milk 2 or 3 times a day, every 2 to 3 hours to continue exclusively breastfeeding. If you can only get one break a day and you are unable to pump a full day's allotment in one pumping, a supplemental bottle of formula may be needed. Be aware however, if bottles of formula are given regularly, your milk supply will decrease accordingly.
Many mothers learn that their babies nurse more frequently in the evenings on days they work.
Feed on demand when you are with your baby. If possible, arrange to nurse your baby at lunch time. There are a number of breast pumps on the market, with varying degrees of comfort, efficiency and cost. Most require time to develop the skills to use them. Your local lactation consultant can help you make realistic plans and guide you to a supportive breast pump depot.