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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 December 20th, 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
Saturday November 15th, 2014 35W, 0D 0.01% 0.02% 0.01% 0.02% -% 0.1% 0.1% 0.2%
Sunday November 16th, 2014 35W, 1D 0.01% 0.03% 0.01% 0.03% -% 0.1% 0.2% 0.3%
Monday November 17th, 2014 35W, 2D 0.02% 0.05% 0.02% 0.05% -% 0.1% 0.2% 0.4%
Tuesday November 18th, 2014 35W, 3D 0.02% 0.07% 0.02% 0.07% -% 0.1% 0.3% 0.6%
Wednesday November 19th, 2014 35W, 4D 0.03% 0.1% 0.03% 0.1% -% 0.2% 0.4% 0.7%
Thursday November 20th, 2014 35W, 5D 0.04% 0.13% 0.04% 0.13% -% 0.2% 0.5% 0.9%
Friday November 21st, 2014 35W, 6D 0.06% 0.19% 0.06% 0.19% 0.1% 0.3% 0.6% 1.2%
Saturday November 22nd, 2014 36W, 0D 0.08% 0.26% 0.08% 0.26% 0.1% 0.4% 0.8% 1.5%
Sunday November 23rd, 2014 36W, 1D 0.1% 0.35% 0.1% 0.35% 0.1% 0.5% 1% 1.9%
Monday November 24th, 2014 36W, 2D 0.14% 0.47% 0.14% 0.47% 0.1% 0.6% 1.3% 2.4%
Tuesday November 25th, 2014 36W, 3D 0.18% 0.62% 0.18% 0.62% 0.2% 0.8% 1.7% 3%
Wednesday November 26th, 2014 36W, 4D 0.22% 0.82% 0.22% 0.82% 0.2% 1% 2.1% 3.7%
Thursday November 27th, 2014 36W, 5D 0.28% 1.07% 0.28% 1.07% 0.3% 1.2% 2.5% 4.5%
Friday November 28th, 2014 36W, 6D 0.35% 1.39% 0.35% 1.39% 0.4% 1.5% 3.1% 5.4%
Saturday November 29th, 2014 37W, 0D 0.44% 1.79% 0.44% 1.79% 0.4% 1.8% 3.8% 6.4%
Sunday November 30th, 2014 37W, 1D 0.54% 2.28% 0.54% 2.28% 0.6% 2.2% 4.5% 7.6%
Monday December 1st, 2014 37W, 2D 0.66% 2.87% 0.66% 2.87% 0.7% 2.7% 5.4% 8.9%
Tuesday December 2nd, 2014 37W, 3D 0.79% 3.59% 0.79% 3.59% 0.8% 3.2% 6.3% 10.4%
Wednesday December 3rd, 2014 37W, 4D 0.94% 4.46% 0.94% 4.46% 1% 3.8% 7.4% 11.9%
Thursday December 4th, 2014 37W, 5D 1.11% 5.48% 1.11% 5.48% 1.2% 4.4% 8.6% 13.7%
Friday December 5th, 2014 37W, 6D 1.3% 6.68% 1.3% 6.68% 1.4% 5.2% 9.8% 15.5%
Saturday December 6th, 2014 38W, 0D 1.5% 8.08% 1.5% 8.08% 1.6% 6% 11.2% 17.5%
Sunday December 7th, 2014 38W, 1D 1.71% 9.68% 1.71% 9.68% 1.9% 6.9% 12.7% 19.7%
Monday December 8th, 2014 38W, 2D 1.94% 11.51% 1.94% 11.51% 2.2% 7.8% 14.3% 21.9%
Tuesday December 9th, 2014 38W, 3D 2.18% 13.57% 2.18% 13.57% 2.5% 8.8% 16% 24.2%
Wednesday December 10th, 2014 38W, 4D 2.42% 15.87% 2.42% 15.87% 2.9% 9.9% 17.8% 26.6%
Thursday December 11th, 2014 38W, 5D 2.66% 18.41% 2.66% 18.41% 3.3% 11.1% 19.7% 29%
Friday December 12th, 2014 38W, 6D 2.9% 21.19% 2.9% 21.19% 3.7% 12.3% 21.6% 31.5%
Saturday December 13th, 2014 39W, 0D 3.12% 24.2% 3.12% 24.2% 4.1% 13.5% 23.6% 34%
Sunday December 14th, 2014 39W, 1D 3.33% 27.43% 3.33% 27.43% 4.6% 14.9% 25.6% 36.6%
Monday December 15th, 2014 39W, 2D 3.52% 30.85% 3.52% 30.85% 5.1% 16.2% 27.7% 39.2%
Tuesday December 16th, 2014 39W, 3D 3.68% 34.46% 3.68% 34.46% 5.6% 17.6% 29.8% 41.7%
Wednesday December 17th, 2014 39W, 4D 3.81% 38.21% 3.81% 38.21% 6.2% 19.1% 31.9% 44.2%
Thursday December 18th, 2014 39W, 5D 3.91% 42.07% 3.91% 42.07% 6.7% 20.6% 34% 46.7%
Friday December 19th, 2014 39W, 6D 3.97% 46.02% 3.97% 46.02% 7.4% 22.1% 36.2% 49.2%
Saturday December 20th, 2014 40W, 0D 3.99% 50% 3.99% 50% 8% 23.6% 38.3% 51.6%
Sunday December 21st, 2014 40W, 1D 3.97% 53.98% 3.97% 53.98% 8.6% 25.1% 40.4% 54%
Monday December 22nd, 2014 40W, 2D 3.91% 57.93% 3.91% 57.93% 9.3% 26.7% 42.5% 56.2%
Tuesday December 23rd, 2014 40W, 3D 3.81% 61.79% 3.81% 61.79% 10% 28.2% 44.5% 58.5%
Wednesday December 24th, 2014 40W, 4D 3.68% 65.54% 3.68% 65.54% 10.7% 29.8% 46.6% 60.6%
Thursday December 25th, 2014 40W, 5D 3.52% 69.15% 3.52% 69.15% 11.4% 31.3% 48.6% 62.7%
Friday December 26th, 2014 40W, 6D 3.33% 72.57% 3.33% 72.57% 12.1% 32.9% 50.5% 64.7%
Saturday December 27th, 2014 41W, 0D 3.12% 75.8% 3.12% 75.8% 12.9% 34.4% 52.4% 66.6%
Sunday December 28th, 2014 41W, 1D 2.9% 78.81% 2.9% 78.81% 13.7% 36% 54.3% 68.5%
Monday December 29th, 2014 41W, 2D 2.66% 81.59% 2.66% 81.59% 14.4% 37.5% 56.1% 70.2%
Tuesday December 30th, 2014 41W, 3D 2.42% 84.13% 2.42% 84.13% 15.2% 39% 57.9% 71.9%
Wednesday December 31st, 2014 41W, 4D 2.18% 86.43% 2.18% 86.43% 16.1% 40.5% 59.6% 73.5%
Thursday January 1st, 2015 41W, 5D 1.94% 88.49% 1.94% 88.49% 16.9% 42% 61.3% 75.1%
Friday January 2nd, 2015 41W, 6D 1.71% 90.32% 1.71% 90.32% 17.7% 43.4% 62.9% 76.4%
Saturday January 3rd, 2015 42W, 0D 1.5% 91.92% 1.5% 91.92% 18.6% 44.8% 64.5% 77.8%
Sunday January 4th, 2015 42W, 1D 1.3% 93.32% 1.3% 93.32% 19.5% 46.3% 65.9% 79.2%
Monday January 5th, 2015 42W, 2D 1.11% 94.52% 1.11% 94.52% 20.3% 47.6% 67.3% 80.5%
Tuesday January 6th, 2015 42W, 3D 0.94% 95.54% 0.94% 95.54% 21.1% 48.9% 68.8% 81.6%
Wednesday January 7th, 2015 42W, 4D 0.79% 96.41% 0.79% 96.41% 22% 50.1% 70.2% 82.7%
Thursday January 8th, 2015 42W, 5D 0.66% 97.13% 0.66% 97.13% 23% 51.6% 71.4% 83.6%
Friday January 9th, 2015 42W, 6D 0.54% 97.72% 0.54% 97.72% 23.7% 53.1% 72.8% 84.6%
Saturday January 10th, 2015 43W, 0D 0.44% 98.21% 0.44% 98.21% 24.6% 54.2% 73.7% 85.5%
Sunday January 11th, 2015 43W, 1D 0.35% 98.61% 0.35% 98.61% 25.2% 55.4% 74.8% 86.3%
Monday January 12th, 2015 43W, 2D 0.28% 98.93% 0.28% 98.93% 26.2% 56.1% 75.7% 87.9%
Tuesday January 13th, 2015 43W, 3D 0.22% 99.18% 0.22% 99.18% 26.8% 57.3% 76.8% -%
Wednesday January 14th, 2015 43W, 4D 0.18% 99.38% 0.18% 99.38% 29% 58.1% 79% -%
Thursday January 15th, 2015 43W, 5D 0.14% 99.53% 0.14% 99.53% 29.8% 59.6% -% -%
Friday January 16th, 2015 43W, 6D 0.1% 99.65% 0.1% 99.65% 28.6% 62.9% -% -%
Saturday January 17th, 2015 44W, 0D 0.08% 99.74% 0.08% 99.74% 30.8% -% -% -%
Sunday January 18th, 2015 44W, 1D 0.06% 99.81% 0.06% 99.81% 31.6% -% -% -%
Monday January 19th, 2015 44W, 2D 0.04% 99.87% 0.04% 99.87% 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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