In your mom’s day, professional women were expected to quit their jobs (or were fired) as soon as they began to show.
Today, most jobs in the U.S. allow for 12 weeks of (unpaid) family leave, and most moms-to-be work for as long as they can to have maximum time to spend with the baby. How long you’ll be able to tolerate doing your job will depend a lot on your health and exactly what it is you do all day. Most women with desk jobs start to get seriously uncomfortable by about week 36, though if your job is physically demanding or involves exposure to dangerous chemicals you may need to leave sooner.
If you’re in robust health you might be able to push it to week 38, or even beyond, though after the start of the 38th week you’ll be “in the zone” for spontaneous labor, with about 40 percent of babies born between weeks 38 and 40.
If you do decide to stay at work beyond the 38th week, write down your hospital’s name and address and your partner and health care provider’s phone numbers, so if you do go into labor or your water breaks at work a trusted co-worker can more easily help you.