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