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I’m currently in the home stretch of my pregnancy and can’t stop stressing about everything, even though I’m healthy and the baby’s growth is on track. How common is it for someone with no risk factors to go into labor way too early?
—Help Me Stop Googling
This is an extremely common worry, even when there is nothing in your history or medical experience suggesting you’re at elevated risk. I remember breathing a sigh of relief in each of my pregnancies when I reached particular milestones — 22 weeks, 25, 28, 34.
The good news is that we have a very comprehensive answer to this question, because the CDC collects detailed data about birth timing and maternal risk factors. The graph below shows the share of births, by week, beginning at 22 weeks for women with no pregnancy risk factors cited in birth certificate data. This means no gestational diabetes, hypertension, or preeclampsia; no history of preterm birth and no pre-pregnancy hypertension or diabetes. This represents about half of births in the U.S. in 2023 (the year of this data).
Among this group, most babies are born in week 39 of pregnancy (about 30%), with week 40 being a close second (20%). There are births at all weeks in the data, but, as you can see, there are so few before about 32 weeks that it is difficult to see in the graph. Only about 1 in 2,000 births, or 0.05% of births, occur in the 22nd week of pregnancy among this group.
Overall, 2.5% of births in this group occurred before 34 weeks, and 9.5% before 37 weeks.
I hope this provides some reassurance that very preterm birth is rare, and more so if you do not have complications. Even with this, some worry is common — almost inevitable — so please take care of yourself.
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Is there any data surrounding pre-term labor if there are risk-factors present? I’m assuming the data will differ based on which risk factor(s), but thought it was worth asking!