This table attempts to estimate your probability of going into labor on different individual days based on your estimated due date. If you don't know your due date, or just want a handy daily page to tell you where you're at, use the pregnancy calendar.
It's based on the idea that the average pregnancy lasts 40 weeks with a standard deviation of about 10 days. This means you're more likely to go into labor on one of the days close to your due date. For instance, about half of all babies are born within a week of their date. Scroll to the bottom of this page if you want to know more about where I got these numbers.
The following dates are based on an estimated due date of September 25th, 2013.
| Date | Progress | Overall odds of spontaneous labor |
Current odds of spontaneous labor |
Odds of a pregnant woman at this stage going into labor | |||||
|---|---|---|---|---|---|---|---|---|---|
| On this date | By this date | On this date | By this date | On this date | Within 3 days | Within 5 days | Within 7 days | ||
| Wednesday August 21st, 2013 | 35W, 0D | 0.01% | 0.02% | 0.01% | 0.02% | -% | 0.1% | 0.1% | 0.2% |
| Thursday August 22nd, 2013 | 35W, 1D | 0.01% | 0.03% | 0.01% | 0.03% | -% | 0.1% | 0.2% | 0.3% |
| Friday August 23rd, 2013 | 35W, 2D | 0.02% | 0.05% | 0.02% | 0.05% | -% | 0.1% | 0.2% | 0.4% |
| Saturday August 24th, 2013 | 35W, 3D | 0.02% | 0.07% | 0.02% | 0.07% | -% | 0.1% | 0.3% | 0.6% |
| Sunday August 25th, 2013 | 35W, 4D | 0.03% | 0.1% | 0.03% | 0.1% | -% | 0.2% | 0.4% | 0.7% |
| Monday August 26th, 2013 | 35W, 5D | 0.04% | 0.13% | 0.04% | 0.13% | -% | 0.2% | 0.5% | 0.9% |
| Tuesday August 27th, 2013 | 35W, 6D | 0.06% | 0.19% | 0.06% | 0.19% | 0.1% | 0.3% | 0.6% | 1.2% |
| Wednesday August 28th, 2013 | 36W, 0D | 0.08% | 0.26% | 0.08% | 0.26% | 0.1% | 0.4% | 0.8% | 1.5% |
| Thursday August 29th, 2013 | 36W, 1D | 0.1% | 0.35% | 0.1% | 0.35% | 0.1% | 0.5% | 1% | 1.9% |
| Friday August 30th, 2013 | 36W, 2D | 0.14% | 0.47% | 0.14% | 0.47% | 0.1% | 0.6% | 1.3% | 2.4% |
| Saturday August 31st, 2013 | 36W, 3D | 0.18% | 0.62% | 0.18% | 0.62% | 0.2% | 0.8% | 1.7% | 3% |
| Sunday September 1st, 2013 | 36W, 4D | 0.22% | 0.82% | 0.22% | 0.82% | 0.2% | 1% | 2.1% | 3.7% |
| Monday September 2nd, 2013 | 36W, 5D | 0.28% | 1.07% | 0.28% | 1.07% | 0.3% | 1.2% | 2.5% | 4.5% |
| Tuesday September 3rd, 2013 | 36W, 6D | 0.35% | 1.39% | 0.35% | 1.39% | 0.4% | 1.5% | 3.1% | 5.4% |
| Wednesday September 4th, 2013 | 37W, 0D | 0.44% | 1.79% | 0.44% | 1.79% | 0.4% | 1.8% | 3.8% | 6.4% |
| Thursday September 5th, 2013 | 37W, 1D | 0.54% | 2.28% | 0.54% | 2.28% | 0.6% | 2.2% | 4.5% | 7.6% |
| Friday September 6th, 2013 | 37W, 2D | 0.66% | 2.87% | 0.66% | 2.87% | 0.7% | 2.7% | 5.4% | 8.9% |
| Saturday September 7th, 2013 | 37W, 3D | 0.79% | 3.59% | 0.79% | 3.59% | 0.8% | 3.2% | 6.3% | 10.4% |
| Sunday September 8th, 2013 | 37W, 4D | 0.94% | 4.46% | 0.94% | 4.46% | 1% | 3.8% | 7.4% | 11.9% |
| Monday September 9th, 2013 | 37W, 5D | 1.11% | 5.48% | 1.11% | 5.48% | 1.2% | 4.4% | 8.6% | 13.7% |
| Tuesday September 10th, 2013 | 37W, 6D | 1.3% | 6.68% | 1.3% | 6.68% | 1.4% | 5.2% | 9.8% | 15.5% |
| Wednesday September 11th, 2013 | 38W, 0D | 1.5% | 8.08% | 1.5% | 8.08% | 1.6% | 6% | 11.2% | 17.5% |
| Thursday September 12th, 2013 | 38W, 1D | 1.71% | 9.68% | 1.71% | 9.68% | 1.9% | 6.9% | 12.7% | 19.7% |
| Friday September 13th, 2013 | 38W, 2D | 1.94% | 11.51% | 1.94% | 11.51% | 2.2% | 7.8% | 14.3% | 21.9% |
| Saturday September 14th, 2013 | 38W, 3D | 2.18% | 13.57% | 2.18% | 13.57% | 2.5% | 8.8% | 16% | 24.2% |
| Sunday September 15th, 2013 | 38W, 4D | 2.42% | 15.87% | 2.42% | 15.87% | 2.9% | 9.9% | 17.8% | 26.6% |
| Monday September 16th, 2013 | 38W, 5D | 2.66% | 18.41% | 2.66% | 18.41% | 3.3% | 11.1% | 19.7% | 29% |
| Tuesday September 17th, 2013 | 38W, 6D | 2.9% | 21.19% | 2.9% | 21.19% | 3.7% | 12.3% | 21.6% | 31.5% |
| Wednesday September 18th, 2013 | 39W, 0D | 3.12% | 24.2% | 3.12% | 24.2% | 4.1% | 13.5% | 23.6% | 34% |
| Thursday September 19th, 2013 | 39W, 1D | 3.33% | 27.43% | 3.33% | 27.43% | 4.6% | 14.9% | 25.6% | 36.6% |
| Friday September 20th, 2013 | 39W, 2D | 3.52% | 30.85% | 3.52% | 30.85% | 5.1% | 16.2% | 27.7% | 39.2% |
| Saturday September 21st, 2013 | 39W, 3D | 3.68% | 34.46% | 3.68% | 34.46% | 5.6% | 17.6% | 29.8% | 41.7% |
| Sunday September 22nd, 2013 | 39W, 4D | 3.81% | 38.21% | 3.81% | 38.21% | 6.2% | 19.1% | 31.9% | 44.2% |
| Monday September 23rd, 2013 | 39W, 5D | 3.91% | 42.07% | 3.91% | 42.07% | 6.7% | 20.6% | 34% | 46.7% |
| Tuesday September 24th, 2013 | 39W, 6D | 3.97% | 46.02% | 3.97% | 46.02% | 7.4% | 22.1% | 36.2% | 49.2% |
| Wednesday September 25th, 2013 | 40W, 0D | 3.99% | 50% | 3.99% | 50% | 8% | 23.6% | 38.3% | 51.6% |
| Thursday September 26th, 2013 | 40W, 1D | 3.97% | 53.98% | 3.97% | 53.98% | 8.6% | 25.1% | 40.4% | 54% |
| Friday September 27th, 2013 | 40W, 2D | 3.91% | 57.93% | 3.91% | 57.93% | 9.3% | 26.7% | 42.5% | 56.2% |
| Saturday September 28th, 2013 | 40W, 3D | 3.81% | 61.79% | 3.81% | 61.79% | 10% | 28.2% | 44.5% | 58.5% |
| Sunday September 29th, 2013 | 40W, 4D | 3.68% | 65.54% | 3.68% | 65.54% | 10.7% | 29.8% | 46.6% | 60.6% |
| Monday September 30th, 2013 | 40W, 5D | 3.52% | 69.15% | 3.52% | 69.15% | 11.4% | 31.3% | 48.6% | 62.7% |
| Tuesday October 1st, 2013 | 40W, 6D | 3.33% | 72.57% | 3.33% | 72.57% | 12.1% | 32.9% | 50.5% | 64.7% |
| Wednesday October 2nd, 2013 | 41W, 0D | 3.12% | 75.8% | 3.12% | 75.8% | 12.9% | 34.4% | 52.4% | 66.6% |
| Thursday October 3rd, 2013 | 41W, 1D | 2.9% | 78.81% | 2.9% | 78.81% | 13.7% | 36% | 54.3% | 68.5% |
| Friday October 4th, 2013 | 41W, 2D | 2.66% | 81.59% | 2.66% | 81.59% | 14.4% | 37.5% | 56.1% | 70.2% |
| Saturday October 5th, 2013 | 41W, 3D | 2.42% | 84.13% | 2.42% | 84.13% | 15.2% | 39% | 57.9% | 71.9% |
| Sunday October 6th, 2013 | 41W, 4D | 2.18% | 86.43% | 2.18% | 86.43% | 16.1% | 40.5% | 59.6% | 73.5% |
| Monday October 7th, 2013 | 41W, 5D | 1.94% | 88.49% | 1.94% | 88.49% | 16.9% | 42% | 61.3% | 75.1% |
| Tuesday October 8th, 2013 | 41W, 6D | 1.71% | 90.32% | 1.71% | 90.32% | 17.7% | 43.4% | 62.9% | 76.4% |
| Wednesday October 9th, 2013 | 42W, 0D | 1.5% | 91.92% | 1.5% | 91.92% | 18.6% | 44.8% | 64.5% | 77.8% |
| Thursday October 10th, 2013 | 42W, 1D | 1.3% | 93.32% | 1.3% | 93.32% | 19.5% | 46.3% | 65.9% | 79.2% |
| Friday October 11th, 2013 | 42W, 2D | 1.11% | 94.52% | 1.11% | 94.52% | 20.3% | 47.6% | 67.3% | 80.5% |
| Saturday October 12th, 2013 | 42W, 3D | 0.94% | 95.54% | 0.94% | 95.54% | 21.1% | 48.9% | 68.8% | 81.6% |
| Sunday October 13th, 2013 | 42W, 4D | 0.79% | 96.41% | 0.79% | 96.41% | 22% | 50.1% | 70.2% | 82.7% |
| Monday October 14th, 2013 | 42W, 5D | 0.66% | 97.13% | 0.66% | 97.13% | 23% | 51.6% | 71.4% | 83.6% |
| Tuesday October 15th, 2013 | 42W, 6D | 0.54% | 97.72% | 0.54% | 97.72% | 23.7% | 53.1% | 72.8% | 84.6% |
| Wednesday October 16th, 2013 | 43W, 0D | 0.44% | 98.21% | 0.44% | 98.21% | 24.6% | 54.2% | 73.7% | 85.5% |
| Thursday October 17th, 2013 | 43W, 1D | 0.35% | 98.61% | 0.35% | 98.61% | 25.2% | 55.4% | 74.8% | 86.3% |
| Friday October 18th, 2013 | 43W, 2D | 0.28% | 98.93% | 0.28% | 98.93% | 26.2% | 56.1% | 75.7% | 87.9% |
| Saturday October 19th, 2013 | 43W, 3D | 0.22% | 99.18% | 0.22% | 99.18% | 26.8% | 57.3% | 76.8% | -% |
| Sunday October 20th, 2013 | 43W, 4D | 0.18% | 99.38% | 0.18% | 99.38% | 29% | 58.1% | 79% | -% |
| Monday October 21st, 2013 | 43W, 5D | 0.14% | 99.53% | 0.14% | 99.53% | 29.8% | 59.6% | -% | -% |
| Tuesday October 22nd, 2013 | 43W, 6D | 0.1% | 99.65% | 0.1% | 99.65% | 28.6% | 62.9% | -% | -% |
| Wednesday October 23rd, 2013 | 44W, 0D | 0.08% | 99.74% | 0.08% | 99.74% | 30.8% | -% | -% | -% |
| Thursday October 24th, 2013 | 44W, 1D | 0.06% | 99.81% | 0.06% | 99.81% | 31.6% | -% | -% | -% |
| Friday October 25th, 2013 | 44W, 2D | 0.04% | 99.87% | 0.04% | 99.87% | 30.8% | -% | -% | -% |
All percentages are estimates based on mathematical averages and should not be taken terribly seriously... just because you only have 5% chance of going into labor two weeks early, that doesn't mean you should schedule a trip to the bahamas that weekend (see xkcd to get what I mean here).
You should (obviously) listen to your doctor or midwife on all matters related to pregnancy and childbirth. Just because this chart tells you that a 42W pregnant woman has a high chance of delivering in the next seven days, it doesn't mean it's healthy for her to be pregnant for seven more days. If your doctor wants to increase odds of delivery by inducing labor, there's probably a good reason.
Finding good distribution statistics on spontaneous labor is interesting. I have not found a study with an exact daily breakdown of when babies are born. However I have read way too much on this topic, so I can tell you that my favorite published research is The length of human pregnancy as calculated by ultrasonographic measurement of the fetal biparietal diameter (H. Kieler, O. Axelsson, S. Nilsson, U. Waldenströ) which a very nice table of 10 published studies, which found various means between 272-283 days. The study contributes their own results as well, analyzing nearly 2000 mothers who went into labor spontaneously, and there's graphs of what they found. They found a mean around 280 days, and standard deviations between 8-11 days. There's a big list of other studies and answers in the Introduction to my due date survey results.
Which leads to this topic... I am also in the process of collecting my own statistics. If you have had a baby, please take my due date survey. Oddly enough, the numbers I've collected so far support my messy hunch that pregnancy length has a 40-week mean and 9-10 day standard deviation. So go me.
Anyway if you have better research, drop me an e-mail (spacefem@spacefem.com).
Charts are generated by flot.