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Pregnancy Due Date Ranges

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 October 24th, 2014.

Change due date:
Month Day Year
Date Progress Overall probability of
spontaneous labor
Current probability of
spontaneous labor
probability 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
Friday September 19th, 2014 35W, 0D 0.01% 0.02% -% -% -% 0.1% 0.1% 0.2%
Saturday September 20th, 2014 35W, 1D 0.01% 0.03% -% -% -% 0.1% 0.2% 0.3%
Sunday September 21st, 2014 35W, 2D 0.02% 0.05% -% -% -% 0.1% 0.2% 0.4%
Monday September 22nd, 2014 35W, 3D 0.02% 0.07% -% -% -% 0.1% 0.3% 0.6%
Tuesday September 23rd, 2014 35W, 4D 0.03% 0.1% -% -% -% 0.2% 0.4% 0.7%
Wednesday September 24th, 2014 35W, 5D 0.04% 0.13% -% -% -% 0.2% 0.5% 0.9%
Thursday September 25th, 2014 35W, 6D 0.06% 0.19% -% -% 0.1% 0.3% 0.6% 1.2%
Friday September 26th, 2014 36W, 0D 0.08% 0.26% -% -% 0.1% 0.4% 0.8% 1.5%
Saturday September 27th, 2014 36W, 1D 0.1% 0.35% -% -% 0.1% 0.5% 1% 1.9%
Sunday September 28th, 2014 36W, 2D 0.14% 0.47% -% -% 0.1% 0.6% 1.3% 2.4%
Monday September 29th, 2014 36W, 3D 0.18% 0.62% -% -% 0.2% 0.8% 1.7% 3%
Tuesday September 30th, 2014 36W, 4D 0.22% 0.82% -% -% 0.2% 1% 2.1% 3.7%
Wednesday October 1st, 2014 36W, 5D 0.28% 1.07% -% -% 0.3% 1.2% 2.5% 4.5%
Thursday October 2nd, 2014 36W, 6D 0.35% 1.39% -% -% 0.4% 1.5% 3.1% 5.4%
Friday October 3rd, 2014 37W, 0D 0.44% 1.79% -% -% 0.4% 1.8% 3.8% 6.4%
Saturday October 4th, 2014 37W, 1D 0.54% 2.28% -% -% 0.6% 2.2% 4.5% 7.6%
Sunday October 5th, 2014 37W, 2D 0.66% 2.87% -% -% 0.7% 2.7% 5.4% 8.9%
Monday October 6th, 2014 37W, 3D 0.79% 3.59% -% -% 0.8% 3.2% 6.3% 10.4%
Tuesday October 7th, 2014 37W, 4D 0.94% 4.46% -% -% 1% 3.8% 7.4% 11.9%
Wednesday October 8th, 2014 37W, 5D 1.11% 5.48% -% -% 1.2% 4.4% 8.6% 13.7%
Thursday October 9th, 2014 37W, 6D 1.3% 6.68% -% -% 1.4% 5.2% 9.8% 15.5%
Friday October 10th, 2014 38W, 0D 1.5% 8.08% -% -% 1.6% 6% 11.2% 17.5%
Saturday October 11th, 2014 38W, 1D 1.71% 9.68% -% -% 1.9% 6.9% 12.7% 19.7%
Sunday October 12th, 2014 38W, 2D 1.94% 11.51% -% -% 2.2% 7.8% 14.3% 21.9%
Monday October 13th, 2014 38W, 3D 2.18% 13.57% -% -% 2.5% 8.8% 16% 24.2%
Tuesday October 14th, 2014 38W, 4D 2.42% 15.87% -% -% 2.9% 9.9% 17.8% 26.6%
Wednesday October 15th, 2014 38W, 5D 2.66% 18.41% -% -% 3.3% 11.1% 19.7% 29%
Thursday October 16th, 2014 38W, 6D 2.9% 21.19% -% -% 3.7% 12.3% 21.6% 31.5%
Friday October 17th, 2014 39W, 0D 3.12% 24.2% -% -% 4.1% 13.5% 23.6% 34%
Saturday October 18th, 2014 39W, 1D 3.33% 27.43% -% -% 4.6% 14.9% 25.6% 36.6%
Sunday October 19th, 2014 39W, 2D 3.52% 30.85% -% -% 5.1% 16.2% 27.7% 39.2%
Monday October 20th, 2014 39W, 3D 3.68% 34.46% -% -% 5.6% 17.6% 29.8% 41.7%
Tuesday October 21st, 2014 39W, 4D 3.81% 38.21% -% -% 6.2% 19.1% 31.9% 44.2%
Wednesday October 22nd, 2014 39W, 5D 3.91% 42.07% -% -% 6.7% 20.6% 34% 46.7%
Thursday October 23rd, 2014 39W, 6D 3.97% 46.02% -% -% 7.4% 22.1% 36.2% 49.2%
Friday October 24th, 2014 40W, 0D 3.99% 50% -% -% 8% 23.6% 38.3% 51.6%
Saturday October 25th, 2014 40W, 1D 3.97% 53.98% 7.9% 8% 8.6% 25.1% 40.4% 54%
Sunday October 26th, 2014 40W, 2D 3.91% 57.93% 7.8% 15.9% 9.3% 26.7% 42.5% 56.2%
Monday October 27th, 2014 40W, 3D 3.81% 61.79% 7.6% 23.6% 10% 28.2% 44.5% 58.5%
Tuesday October 28th, 2014 40W, 4D 3.68% 65.54% 7.4% 31.1% 10.7% 29.8% 46.6% 60.6%
Wednesday October 29th, 2014 40W, 5D 3.52% 69.15% 7% 38.3% 11.4% 31.3% 48.6% 62.7%
Thursday October 30th, 2014 40W, 6D 3.33% 72.57% 6.7% 45.1% 12.1% 32.9% 50.5% 64.7%
Friday October 31st, 2014 41W, 0D 3.12% 75.8% 6.2% 51.6% 12.9% 34.4% 52.4% 66.6%
Saturday November 1st, 2014 41W, 1D 2.9% 78.81% 5.8% 57.6% 13.7% 36% 54.3% 68.5%
Sunday November 2nd, 2014 41W, 2D 2.66% 81.59% 5.3% 63.2% 14.4% 37.5% 56.1% 70.2%
Monday November 3rd, 2014 41W, 3D 2.42% 84.13% 4.8% 68.3% 15.2% 39% 57.9% 71.9%
Tuesday November 4th, 2014 41W, 4D 2.18% 86.43% 4.4% 72.9% 16.1% 40.5% 59.6% 73.5%
Wednesday November 5th, 2014 41W, 5D 1.94% 88.49% 3.9% 77% 16.9% 42% 61.3% 75.1%
Thursday November 6th, 2014 41W, 6D 1.71% 90.32% 3.4% 80.6% 17.7% 43.4% 62.9% 76.4%
Friday November 7th, 2014 42W, 0D 1.5% 91.92% 3% 83.8% 18.6% 44.8% 64.5% 77.8%
Saturday November 8th, 2014 42W, 1D 1.3% 93.32% 2.6% 86.6% 19.5% 46.3% 65.9% 79.2%
Sunday November 9th, 2014 42W, 2D 1.11% 94.52% 2.2% 89% 20.3% 47.6% 67.3% 80.5%
Monday November 10th, 2014 42W, 3D 0.94% 95.54% 1.9% 91.1% 21.1% 48.9% 68.8% 81.6%
Tuesday November 11th, 2014 42W, 4D 0.79% 96.41% 1.6% 92.8% 22% 50.1% 70.2% 82.7%
Wednesday November 12th, 2014 42W, 5D 0.66% 97.13% 1.3% 94.3% 23% 51.6% 71.4% 83.6%
Thursday November 13th, 2014 42W, 6D 0.54% 97.72% 1.1% 95.4% 23.7% 53.1% 72.8% 84.6%
Friday November 14th, 2014 43W, 0D 0.44% 98.21% 0.9% 96.4% 24.6% 54.2% 73.7% 85.5%
Saturday November 15th, 2014 43W, 1D 0.35% 98.61% 0.7% 97.2% 25.2% 55.4% 74.8% 86.3%
Sunday November 16th, 2014 43W, 2D 0.28% 98.93% 0.6% 97.9% 26.2% 56.1% 75.7% 87.9%
Monday November 17th, 2014 43W, 3D 0.22% 99.18% 0.4% 98.4% 26.8% 57.3% 76.8% -%
Tuesday November 18th, 2014 43W, 4D 0.18% 99.38% 0.4% 98.8% 29% 58.1% 79% -%
Wednesday November 19th, 2014 43W, 5D 0.14% 99.53% 0.3% 99.1% 29.8% 59.6% -% -%
Thursday November 20th, 2014 43W, 6D 0.1% 99.65% 0.2% 99.3% 28.6% 62.9% -% -%
Friday November 21st, 2014 44W, 0D 0.08% 99.74% 0.2% 99.5% 30.8% -% -% -%
Saturday November 22nd, 2014 44W, 1D 0.06% 99.81% 0.1% 99.6% 31.6% -% -% -%
Sunday November 23rd, 2014 44W, 2D 0.04% 99.87% 0.1% 99.7% 30.8% -% -% -%

Probability of labor on a given day

Probability of labor by a given day

Notes and disclaimers

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 probability 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.

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