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 September 5th, 2019.

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
Thursday August 1st, 2019 35W, 0D 0.01% 0.02% -% -% -% 0.1% 0.1% 0.2%
Friday August 2nd, 2019 35W, 1D 0.01% 0.03% -% -% -% 0.1% 0.2% 0.3%
Saturday August 3rd, 2019 35W, 2D 0.02% 0.05% -% -% -% 0.1% 0.2% 0.4%
Sunday August 4th, 2019 35W, 3D 0.02% 0.07% -% -% -% 0.1% 0.3% 0.6%
Monday August 5th, 2019 35W, 4D 0.03% 0.1% -% -% -% 0.2% 0.4% 0.7%
Tuesday August 6th, 2019 35W, 5D 0.04% 0.13% -% -% -% 0.2% 0.5% 0.9%
Wednesday August 7th, 2019 35W, 6D 0.06% 0.19% -% -% 0.1% 0.3% 0.6% 1.2%
Thursday August 8th, 2019 36W, 0D 0.08% 0.26% -% -% 0.1% 0.4% 0.8% 1.5%
Friday August 9th, 2019 36W, 1D 0.1% 0.35% -% -% 0.1% 0.5% 1% 1.9%
Saturday August 10th, 2019 36W, 2D 0.14% 0.47% -% -% 0.1% 0.6% 1.3% 2.4%
Sunday August 11th, 2019 36W, 3D 0.18% 0.62% -% -% 0.2% 0.8% 1.7% 3%
Monday August 12th, 2019 36W, 4D 0.22% 0.82% -% -% 0.2% 1% 2.1% 3.7%
Tuesday August 13th, 2019 36W, 5D 0.28% 1.07% -% -% 0.3% 1.2% 2.5% 4.5%
Wednesday August 14th, 2019 36W, 6D 0.35% 1.39% -% -% 0.4% 1.5% 3.1% 5.4%
Thursday August 15th, 2019 37W, 0D 0.44% 1.79% -% -% 0.4% 1.8% 3.8% 6.4%
Friday August 16th, 2019 37W, 1D 0.54% 2.28% -% -% 0.6% 2.2% 4.5% 7.6%
Saturday August 17th, 2019 37W, 2D 0.66% 2.87% -% -% 0.7% 2.7% 5.4% 8.9%
Sunday August 18th, 2019 37W, 3D 0.79% 3.59% -% -% 0.8% 3.2% 6.3% 10.4%
Monday August 19th, 2019 37W, 4D 0.94% 4.46% -% -% 1% 3.8% 7.4% 11.9%
Tuesday August 20th, 2019 37W, 5D 1.11% 5.48% -% -% 1.2% 4.4% 8.6% 13.7%
Wednesday August 21st, 2019 37W, 6D 1.3% 6.68% -% -% 1.4% 5.2% 9.8% 15.5%
Thursday August 22nd, 2019 38W, 0D 1.5% 8.08% -% -% 1.6% 6% 11.2% 17.5%
Friday August 23rd, 2019 38W, 1D 1.71% 9.68% -% -% 1.9% 6.9% 12.7% 19.7%
Saturday August 24th, 2019 38W, 2D 1.94% 11.51% -% -% 2.2% 7.8% 14.3% 21.9%
Sunday August 25th, 2019 38W, 3D 2.18% 13.57% -% -% 2.5% 8.8% 16% 24.2%
Monday August 26th, 2019 38W, 4D 2.42% 15.87% -% -% 2.9% 9.9% 17.8% 26.6%
Tuesday August 27th, 2019 38W, 5D 2.66% 18.41% -% -% 3.3% 11.1% 19.7% 29%
Wednesday August 28th, 2019 38W, 6D 2.9% 21.19% -% -% 3.7% 12.3% 21.6% 31.5%
Thursday August 29th, 2019 39W, 0D 3.12% 24.2% -% -% 4.1% 13.5% 23.6% 34%
Friday August 30th, 2019 39W, 1D 3.33% 27.43% -% -% 4.6% 14.9% 25.6% 36.6%
Saturday August 31st, 2019 39W, 2D 3.52% 30.85% -% -% 5.1% 16.2% 27.7% 39.2%
Sunday September 1st, 2019 39W, 3D 3.68% 34.46% -% -% 5.6% 17.6% 29.8% 41.7%
Monday September 2nd, 2019 39W, 4D 3.81% 38.21% -% -% 6.2% 19.1% 31.9% 44.2%
Tuesday September 3rd, 2019 39W, 5D 3.91% 42.07% -% -% 6.7% 20.6% 34% 46.7%
Wednesday September 4th, 2019 39W, 6D 3.97% 46.02% -% -% 7.4% 22.1% 36.2% 49.2%
Thursday September 5th, 2019 40W, 0D 3.99% 50% -% -% 8% 23.6% 38.3% 51.6%
Friday September 6th, 2019 40W, 1D 3.97% 53.98% -% -% 8.6% 25.1% 40.4% 54%
Saturday September 7th, 2019 40W, 2D 3.91% 57.93% -% -% 9.3% 26.7% 42.5% 56.2%
Sunday September 8th, 2019 40W, 3D 3.81% 61.79% -% -% 10% 28.2% 44.5% 58.5%
Monday September 9th, 2019 40W, 4D 3.68% 65.54% -% -% 10.7% 29.8% 46.6% 60.6%
Tuesday September 10th, 2019 40W, 5D 3.52% 69.15% -% -% 11.4% 31.3% 48.6% 62.7%
Wednesday September 11th, 2019 40W, 6D 3.33% 72.57% -% -% 12.1% 32.9% 50.5% 64.7%
Thursday September 12th, 2019 41W, 0D 3.12% 75.8% -% -% 12.9% 34.4% 52.4% 66.6%
Friday September 13th, 2019 41W, 1D 2.9% 78.81% -% -% 13.7% 36% 54.3% 68.5%
Saturday September 14th, 2019 41W, 2D 2.66% 81.59% -% -% 14.4% 37.5% 56.1% 70.2%
Sunday September 15th, 2019 41W, 3D 2.42% 84.13% -% -% 15.2% 39% 57.9% 71.9%
Monday September 16th, 2019 41W, 4D 2.18% 86.43% -% -% 16.1% 40.5% 59.6% 73.5%
Tuesday September 17th, 2019 41W, 5D 1.94% 88.49% -% -% 16.9% 42% 61.3% 75.1%
Wednesday September 18th, 2019 41W, 6D 1.71% 90.32% -% -% 17.7% 43.4% 62.9% 76.4%
Thursday September 19th, 2019 42W, 0D 1.5% 91.92% -% -% 18.6% 44.8% 64.5% 77.8%
Friday September 20th, 2019 42W, 1D 1.3% 93.32% -% -% 19.5% 46.3% 65.9% 79.2%
Saturday September 21st, 2019 42W, 2D 1.11% 94.52% -% -% 20.3% 47.6% 67.3% 80.5%
Sunday September 22nd, 2019 42W, 3D 0.94% 95.54% -% -% 21.1% 48.9% 68.8% 81.6%
Monday September 23rd, 2019 42W, 4D 0.79% 96.41% -% -% 22% 50.1% 70.2% 82.7%
Tuesday September 24th, 2019 42W, 5D 0.66% 97.13% -% -% 23% 51.6% 71.4% 83.6%
Wednesday September 25th, 2019 42W, 6D 0.54% 97.72% -% -% 23.7% 53.1% 72.8% 84.6%
Thursday September 26th, 2019 43W, 0D 0.44% 98.21% -% -% 24.6% 54.2% 73.7% 85.5%
Friday September 27th, 2019 43W, 1D 0.35% 98.61% -% -% 25.2% 55.4% 74.8% 86.3%
Saturday September 28th, 2019 43W, 2D 0.28% 98.93% -% -% 26.2% 56.1% 75.7% 87.9%
Sunday September 29th, 2019 43W, 3D 0.22% 99.18% -% -% 26.8% 57.3% 76.8% -%
Monday September 30th, 2019 43W, 4D 0.18% 99.38% -% -% 29% 58.1% 79% -%
Tuesday October 1st, 2019 43W, 5D 0.14% 99.53% -% -% 29.8% 59.6% -% -%
Wednesday October 2nd, 2019 43W, 6D 0.1% 99.65% -% -% 28.6% 62.9% -% -%
Thursday October 3rd, 2019 44W, 0D 0.08% 99.74% -% -% 30.8% -% -% -%
Friday October 4th, 2019 44W, 1D 0.06% 99.81% -% -% 31.6% -% -% -%
Saturday October 5th, 2019 44W, 2D 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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