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 January 23rd, 2021.

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 December 19th, 2020 35W, 0D 0.01% 0.02% -% -% -% 0.1% 0.1% 0.2%
Sunday December 20th, 2020 35W, 1D 0.01% 0.03% -% -% -% 0.1% 0.2% 0.3%
Monday December 21st, 2020 35W, 2D 0.02% 0.05% -% -% -% 0.1% 0.2% 0.4%
Tuesday December 22nd, 2020 35W, 3D 0.02% 0.07% -% -% -% 0.1% 0.3% 0.6%
Wednesday December 23rd, 2020 35W, 4D 0.03% 0.1% -% -% -% 0.2% 0.4% 0.7%
Thursday December 24th, 2020 35W, 5D 0.04% 0.13% -% -% -% 0.2% 0.5% 0.9%
Friday December 25th, 2020 35W, 6D 0.06% 0.19% -% -% 0.1% 0.3% 0.6% 1.2%
Saturday December 26th, 2020 36W, 0D 0.08% 0.26% -% -% 0.1% 0.4% 0.8% 1.5%
Sunday December 27th, 2020 36W, 1D 0.1% 0.35% -% -% 0.1% 0.5% 1% 1.9%
Monday December 28th, 2020 36W, 2D 0.14% 0.47% -% -% 0.1% 0.6% 1.3% 2.4%
Tuesday December 29th, 2020 36W, 3D 0.18% 0.62% -% -% 0.2% 0.8% 1.7% 3%
Wednesday December 30th, 2020 36W, 4D 0.22% 0.82% -% -% 0.2% 1% 2.1% 3.7%
Thursday December 31st, 2020 36W, 5D 0.28% 1.07% -% -% 0.3% 1.2% 2.5% 4.5%
Friday January 1st, 2021 36W, 6D 0.35% 1.39% -% -% 0.4% 1.5% 3.1% 5.4%
Saturday January 2nd, 2021 37W, 0D 0.44% 1.79% -% -% 0.4% 1.8% 3.8% 6.4%
Sunday January 3rd, 2021 37W, 1D 0.54% 2.28% -% -% 0.6% 2.2% 4.5% 7.6%
Monday January 4th, 2021 37W, 2D 0.66% 2.87% -% -% 0.7% 2.7% 5.4% 8.9%
Tuesday January 5th, 2021 37W, 3D 0.79% 3.59% -% -% 0.8% 3.2% 6.3% 10.4%
Wednesday January 6th, 2021 37W, 4D 0.94% 4.46% -% -% 1% 3.8% 7.4% 11.9%
Thursday January 7th, 2021 37W, 5D 1.11% 5.48% -% -% 1.2% 4.4% 8.6% 13.7%
Friday January 8th, 2021 37W, 6D 1.3% 6.68% -% -% 1.4% 5.2% 9.8% 15.5%
Saturday January 9th, 2021 38W, 0D 1.5% 8.08% -% -% 1.6% 6% 11.2% 17.5%
Sunday January 10th, 2021 38W, 1D 1.71% 9.68% -% -% 1.9% 6.9% 12.7% 19.7%
Monday January 11th, 2021 38W, 2D 1.94% 11.51% -% -% 2.2% 7.8% 14.3% 21.9%
Tuesday January 12th, 2021 38W, 3D 2.18% 13.57% -% -% 2.5% 8.8% 16% 24.2%
Wednesday January 13th, 2021 38W, 4D 2.42% 15.87% -% -% 2.9% 9.9% 17.8% 26.6%
Thursday January 14th, 2021 38W, 5D 2.66% 18.41% -% -% 3.3% 11.1% 19.7% 29%
Friday January 15th, 2021 38W, 6D 2.9% 21.19% -% -% 3.7% 12.3% 21.6% 31.5%
Saturday January 16th, 2021 39W, 0D 3.12% 24.2% -% -% 4.1% 13.5% 23.6% 34%
Sunday January 17th, 2021 39W, 1D 3.33% 27.43% -% -% 4.6% 14.9% 25.6% 36.6%
Monday January 18th, 2021 39W, 2D 3.52% 30.85% -% -% 5.1% 16.2% 27.7% 39.2%
Tuesday January 19th, 2021 39W, 3D 3.68% 34.46% -% -% 5.6% 17.6% 29.8% 41.7%
Wednesday January 20th, 2021 39W, 4D 3.81% 38.21% -% -% 6.2% 19.1% 31.9% 44.2%
Thursday January 21st, 2021 39W, 5D 3.91% 42.07% -% -% 6.7% 20.6% 34% 46.7%
Friday January 22nd, 2021 39W, 6D 3.97% 46.02% -% -% 7.4% 22.1% 36.2% 49.2%
Saturday January 23rd, 2021 40W, 0D 3.99% 50% 8% 0% 8% 23.6% 38.3% 51.6%
Sunday January 24th, 2021 40W, 1D 3.97% 53.98% 7.9% 8% 8.6% 25.1% 40.4% 54%
Monday January 25th, 2021 40W, 2D 3.91% 57.93% 7.8% 15.9% 9.3% 26.7% 42.5% 56.2%
Tuesday January 26th, 2021 40W, 3D 3.81% 61.79% 7.6% 23.6% 10% 28.2% 44.5% 58.5%
Wednesday January 27th, 2021 40W, 4D 3.68% 65.54% 7.4% 31.1% 10.7% 29.8% 46.6% 60.6%
Thursday January 28th, 2021 40W, 5D 3.52% 69.15% 7% 38.3% 11.4% 31.3% 48.6% 62.7%
Friday January 29th, 2021 40W, 6D 3.33% 72.57% 6.7% 45.1% 12.1% 32.9% 50.5% 64.7%
Saturday January 30th, 2021 41W, 0D 3.12% 75.8% 6.2% 51.6% 12.9% 34.4% 52.4% 66.6%
Sunday January 31st, 2021 41W, 1D 2.9% 78.81% 5.8% 57.6% 13.7% 36% 54.3% 68.5%
Monday February 1st, 2021 41W, 2D 2.66% 81.59% 5.3% 63.2% 14.4% 37.5% 56.1% 70.2%
Tuesday February 2nd, 2021 41W, 3D 2.42% 84.13% 4.8% 68.3% 15.2% 39% 57.9% 71.9%
Wednesday February 3rd, 2021 41W, 4D 2.18% 86.43% 4.4% 72.9% 16.1% 40.5% 59.6% 73.5%
Thursday February 4th, 2021 41W, 5D 1.94% 88.49% 3.9% 77% 16.9% 42% 61.3% 75.1%
Friday February 5th, 2021 41W, 6D 1.71% 90.32% 3.4% 80.6% 17.7% 43.4% 62.9% 76.4%
Saturday February 6th, 2021 42W, 0D 1.5% 91.92% 3% 83.8% 18.6% 44.8% 64.5% 77.8%
Sunday February 7th, 2021 42W, 1D 1.3% 93.32% 2.6% 86.6% 19.5% 46.3% 65.9% 79.2%
Monday February 8th, 2021 42W, 2D 1.11% 94.52% 2.2% 89% 20.3% 47.6% 67.3% 80.5%
Tuesday February 9th, 2021 42W, 3D 0.94% 95.54% 1.9% 91.1% 21.1% 48.9% 68.8% 81.6%
Wednesday February 10th, 2021 42W, 4D 0.79% 96.41% 1.6% 92.8% 22% 50.1% 70.2% 82.7%
Thursday February 11th, 2021 42W, 5D 0.66% 97.13% 1.3% 94.3% 23% 51.6% 71.4% 83.6%
Friday February 12th, 2021 42W, 6D 0.54% 97.72% 1.1% 95.4% 23.7% 53.1% 72.8% 84.6%
Saturday February 13th, 2021 43W, 0D 0.44% 98.21% 0.9% 96.4% 24.6% 54.2% 73.7% 85.5%
Sunday February 14th, 2021 43W, 1D 0.35% 98.61% 0.7% 97.2% 25.2% 55.4% 74.8% 86.3%
Monday February 15th, 2021 43W, 2D 0.28% 98.93% 0.6% 97.9% 26.2% 56.1% 75.7% 87.9%
Tuesday February 16th, 2021 43W, 3D 0.22% 99.18% 0.4% 98.4% 26.8% 57.3% 76.8% -%
Wednesday February 17th, 2021 43W, 4D 0.18% 99.38% 0.4% 98.8% 29% 58.1% 79% -%
Thursday February 18th, 2021 43W, 5D 0.14% 99.53% 0.3% 99.1% 29.8% 59.6% -% -%
Friday February 19th, 2021 43W, 6D 0.1% 99.65% 0.2% 99.3% 28.6% 62.9% -% -%
Saturday February 20th, 2021 44W, 0D 0.08% 99.74% 0.2% 99.5% 30.8% -% -% -%
Sunday February 21st, 2021 44W, 1D 0.06% 99.81% 0.1% 99.6% 31.6% -% -% -%
Monday February 22nd, 2021 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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