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 March 28th, 2020.

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