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 February 22nd, 2012.
| 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 January 18th, 2012 | 35W, 0D | 0.01% | 0.02% | -% | -% | -% | 0.1% | 0.1% | 0.2% |
| Thursday January 19th, 2012 | 35W, 1D | 0.01% | 0.03% | -% | -% | -% | 0.1% | 0.2% | 0.3% |
| Friday January 20th, 2012 | 35W, 2D | 0.02% | 0.05% | -% | -% | -% | 0.1% | 0.2% | 0.4% |
| Saturday January 21st, 2012 | 35W, 3D | 0.02% | 0.07% | -% | -% | -% | 0.1% | 0.3% | 0.6% |
| Sunday January 22nd, 2012 | 35W, 4D | 0.03% | 0.1% | -% | -% | -% | 0.2% | 0.4% | 0.7% |
| Monday January 23rd, 2012 | 35W, 5D | 0.04% | 0.13% | -% | -% | -% | 0.2% | 0.5% | 0.9% |
| Tuesday January 24th, 2012 | 35W, 6D | 0.06% | 0.19% | -% | -% | 0.1% | 0.3% | 0.6% | 1.2% |
| Wednesday January 25th, 2012 | 36W, 0D | 0.08% | 0.26% | -% | -% | 0.1% | 0.4% | 0.8% | 1.5% |
| Thursday January 26th, 2012 | 36W, 1D | 0.1% | 0.35% | -% | -% | 0.1% | 0.5% | 1% | 1.9% |
| Friday January 27th, 2012 | 36W, 2D | 0.14% | 0.47% | -% | -% | 0.1% | 0.6% | 1.3% | 2.4% |
| Saturday January 28th, 2012 | 36W, 3D | 0.18% | 0.62% | -% | -% | 0.2% | 0.8% | 1.7% | 3% |
| Sunday January 29th, 2012 | 36W, 4D | 0.22% | 0.82% | -% | -% | 0.2% | 1% | 2.1% | 3.7% |
| Monday January 30th, 2012 | 36W, 5D | 0.28% | 1.07% | -% | -% | 0.3% | 1.2% | 2.5% | 4.5% |
| Tuesday January 31st, 2012 | 36W, 6D | 0.35% | 1.39% | -% | -% | 0.4% | 1.5% | 3.1% | 5.4% |
| Wednesday February 1st, 2012 | 37W, 0D | 0.44% | 1.79% | -% | -% | 0.4% | 1.8% | 3.8% | 6.4% |
| Thursday February 2nd, 2012 | 37W, 1D | 0.54% | 2.28% | -% | -% | 0.6% | 2.2% | 4.5% | 7.6% |
| Friday February 3rd, 2012 | 37W, 2D | 0.66% | 2.87% | -% | -% | 0.7% | 2.7% | 5.4% | 8.9% |
| Saturday February 4th, 2012 | 37W, 3D | 0.79% | 3.59% | -% | -% | 0.8% | 3.2% | 6.3% | 10.4% |
| Sunday February 5th, 2012 | 37W, 4D | 0.94% | 4.46% | -% | -% | 1% | 3.8% | 7.4% | 11.9% |
| Monday February 6th, 2012 | 37W, 5D | 1.11% | 5.48% | -% | -% | 1.2% | 4.4% | 8.6% | 13.7% |
| Tuesday February 7th, 2012 | 37W, 6D | 1.3% | 6.68% | -% | -% | 1.4% | 5.2% | 9.8% | 15.5% |
| Wednesday February 8th, 2012 | 38W, 0D | 1.5% | 8.08% | -% | -% | 1.6% | 6% | 11.2% | 17.5% |
| Thursday February 9th, 2012 | 38W, 1D | 1.71% | 9.68% | -% | -% | 1.9% | 6.9% | 12.7% | 19.7% |
| Friday February 10th, 2012 | 38W, 2D | 1.94% | 11.51% | -% | -% | 2.2% | 7.8% | 14.3% | 21.9% |
| Saturday February 11th, 2012 | 38W, 3D | 2.18% | 13.57% | -% | -% | 2.5% | 8.8% | 16% | 24.2% |
| Sunday February 12th, 2012 | 38W, 4D | 2.42% | 15.87% | -% | -% | 2.9% | 9.9% | 17.8% | 26.6% |
| Monday February 13th, 2012 | 38W, 5D | 2.66% | 18.41% | -% | -% | 3.3% | 11.1% | 19.7% | 29% |
| Tuesday February 14th, 2012 | 38W, 6D | 2.9% | 21.19% | -% | -% | 3.7% | 12.3% | 21.6% | 31.5% |
| Wednesday February 15th, 2012 | 39W, 0D | 3.12% | 24.2% | -% | -% | 4.1% | 13.5% | 23.6% | 34% |
| Thursday February 16th, 2012 | 39W, 1D | 3.33% | 27.43% | -% | -% | 4.6% | 14.9% | 25.6% | 36.6% |
| Friday February 17th, 2012 | 39W, 2D | 3.52% | 30.85% | -% | -% | 5.1% | 16.2% | 27.7% | 39.2% |
| Saturday February 18th, 2012 | 39W, 3D | 3.68% | 34.46% | -% | -% | 5.6% | 17.6% | 29.8% | 41.7% |
| Sunday February 19th, 2012 | 39W, 4D | 3.81% | 38.21% | -% | -% | 6.2% | 19.1% | 31.9% | 44.2% |
| Monday February 20th, 2012 | 39W, 5D | 3.91% | 42.07% | -% | -% | 6.7% | 20.6% | 34% | 46.7% |
| Tuesday February 21st, 2012 | 39W, 6D | 3.97% | 46.02% | -% | -% | 7.4% | 22.1% | 36.2% | 49.2% |
| Wednesday February 22nd, 2012 | 40W, 0D | 3.99% | 50% | -% | -% | 8% | 23.6% | 38.3% | 51.6% |
| Thursday February 23rd, 2012 | 40W, 1D | 3.97% | 53.98% | 7.9% | 8% | 8.6% | 25.1% | 40.4% | 54% |
| Friday February 24th, 2012 | 40W, 2D | 3.91% | 57.93% | 7.8% | 15.9% | 9.3% | 26.7% | 42.5% | 56.2% |
| Saturday February 25th, 2012 | 40W, 3D | 3.81% | 61.79% | 7.6% | 23.6% | 10% | 28.2% | 44.5% | 58.5% |
| Sunday February 26th, 2012 | 40W, 4D | 3.68% | 65.54% | 7.4% | 31.1% | 10.7% | 29.8% | 46.6% | 60.6% |
| Monday February 27th, 2012 | 40W, 5D | 3.52% | 69.15% | 7% | 38.3% | 11.4% | 31.3% | 48.6% | 62.7% |
| Tuesday February 28th, 2012 | 40W, 6D | 3.33% | 72.57% | 6.7% | 45.1% | 12.1% | 32.9% | 50.5% | 64.7% |
| Wednesday February 29th, 2012 | 41W, 0D | 3.12% | 75.8% | 6.2% | 51.6% | 12.9% | 34.4% | 52.4% | 66.6% |
| Thursday March 1st, 2012 | 41W, 1D | 2.9% | 78.81% | 5.8% | 57.6% | 13.7% | 36% | 54.3% | 68.5% |
| Friday March 2nd, 2012 | 41W, 2D | 2.66% | 81.59% | 5.3% | 63.2% | 14.4% | 37.5% | 56.1% | 70.2% |
| Saturday March 3rd, 2012 | 41W, 3D | 2.42% | 84.13% | 4.8% | 68.3% | 15.2% | 39% | 57.9% | 71.9% |
| Sunday March 4th, 2012 | 41W, 4D | 2.18% | 86.43% | 4.4% | 72.9% | 16.1% | 40.5% | 59.6% | 73.5% |
| Monday March 5th, 2012 | 41W, 5D | 1.94% | 88.49% | 3.9% | 77% | 16.9% | 42% | 61.3% | 75.1% |
| Tuesday March 6th, 2012 | 41W, 6D | 1.71% | 90.32% | 3.4% | 80.6% | 17.7% | 43.4% | 62.9% | 76.4% |
| Wednesday March 7th, 2012 | 42W, 0D | 1.5% | 91.92% | 3% | 83.8% | 18.6% | 44.8% | 64.5% | 77.8% |
| Thursday March 8th, 2012 | 42W, 1D | 1.3% | 93.32% | 2.6% | 86.6% | 19.5% | 46.3% | 65.9% | 79.2% |
| Friday March 9th, 2012 | 42W, 2D | 1.11% | 94.52% | 2.2% | 89% | 20.3% | 47.6% | 67.3% | 80.5% |
| Saturday March 10th, 2012 | 42W, 3D | 0.94% | 95.54% | 1.9% | 91.1% | 21.1% | 48.9% | 68.8% | 81.6% |
| Sunday March 11th, 2012 | 42W, 4D | 0.79% | 96.41% | 1.6% | 92.8% | 22% | 50.1% | 70.2% | 82.7% |
| Monday March 12th, 2012 | 42W, 5D | 0.66% | 97.13% | 1.3% | 94.3% | 23% | 51.6% | 71.4% | 83.6% |
| Tuesday March 13th, 2012 | 42W, 6D | 0.54% | 97.72% | 1.1% | 95.4% | 23.7% | 53.1% | 72.8% | 84.6% |
| Wednesday March 14th, 2012 | 43W, 0D | 0.44% | 98.21% | 0.9% | 96.4% | 24.6% | 54.2% | 73.7% | 85.5% |
| Thursday March 15th, 2012 | 43W, 1D | 0.35% | 98.61% | 0.7% | 97.2% | 25.2% | 55.4% | 74.8% | 86.3% |
| Friday March 16th, 2012 | 43W, 2D | 0.28% | 98.93% | 0.6% | 97.9% | 26.2% | 56.1% | 75.7% | 87.9% |
| Saturday March 17th, 2012 | 43W, 3D | 0.22% | 99.18% | 0.4% | 98.4% | 26.8% | 57.3% | 76.8% | -% |
| Sunday March 18th, 2012 | 43W, 4D | 0.18% | 99.38% | 0.4% | 98.8% | 29% | 58.1% | 79% | -% |
| Monday March 19th, 2012 | 43W, 5D | 0.14% | 99.53% | 0.3% | 99.1% | 29.8% | 59.6% | -% | -% |
| Tuesday March 20th, 2012 | 43W, 6D | 0.1% | 99.65% | 0.2% | 99.3% | 28.6% | 62.9% | -% | -% |
| Wednesday March 21st, 2012 | 44W, 0D | 0.08% | 99.74% | 0.2% | 99.5% | 30.8% | -% | -% | -% |
| Thursday March 22nd, 2012 | 44W, 1D | 0.06% | 99.81% | 0.1% | 99.6% | 31.6% | -% | -% | -% |
| Friday March 23rd, 2012 | 44W, 2D | 0.04% | 99.87% | 0.1% | 99.7% | 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.