Your odds of spontaneous labor at 37, 38, 39, 40, and 41+ weeks
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These numbers help you plan. All estimates are for spontaneous labor in singleton pregnancies, from NHS Maternity Statistics 2023-24 and CDC data.
37 Weeks
Early Term3-5%
This week
~10%
Cumulative
Early term. Lungs are usually mature. Labor now is common and generally safe, though some babies need extra monitoring.
38 Weeks
Full Term8-10%
This week
~20%
Cumulative
Full term begins. Baby is ready for birth. Braxton Hicks often get stronger around now.
39 Weeks
Full Term15-18%
This week
~35%
Cumulative
Peak readiness. The ARRIVE trial found benefits to induction at 39 weeks for some women. Spontaneous labor becomes more common.
40 Weeks
Due Date20-25%
This week
~55%
Cumulative
Due date week. Statistically the most likely week for spontaneous labor. About half of pregnancies have delivered by now.
41 Weeks
Late Term25-35%*
This week
~80%
Cumulative
Late term. Daily odds are high if you haven't delivered. Most providers discuss induction. *Conditional probability given still pregnant.
42 Weeks
Post-TermVery high*
This week
~100%
Cumulative
Post-term. Nearly all remaining pregnancies deliver this week, spontaneously or with induction. NICE recommends offering induction between 41+0 and 42+0.
What the * means
Probabilities marked * are conditional—'given that you're still pregnant.' At 41 weeks, if you haven't delivered, your odds that week are much higher than the population average. Why? Most women have already had their babies by then.
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Enter your due date to see your personalized odds
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