Spacefem.com

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 3rd, 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
Wednesday July 30th, 2014 35W, 0D 0.01% 0.02% -% -% -% 0.1% 0.1% 0.2%
Thursday July 31st, 2014 35W, 1D 0.01% 0.03% -% -% -% 0.1% 0.2% 0.3%
Friday August 1st, 2014 35W, 2D 0.02% 0.05% -% -% -% 0.1% 0.2% 0.4%
Saturday August 2nd, 2014 35W, 3D 0.02% 0.07% -% -% -% 0.1% 0.3% 0.6%
Sunday August 3rd, 2014 35W, 4D 0.03% 0.1% -% -% -% 0.2% 0.4% 0.7%
Monday August 4th, 2014 35W, 5D 0.04% 0.13% -% -% -% 0.2% 0.5% 0.9%
Tuesday August 5th, 2014 35W, 6D 0.06% 0.19% -% -% 0.1% 0.3% 0.6% 1.2%
Wednesday August 6th, 2014 36W, 0D 0.08% 0.26% -% -% 0.1% 0.4% 0.8% 1.5%
Thursday August 7th, 2014 36W, 1D 0.1% 0.35% -% -% 0.1% 0.5% 1% 1.9%
Friday August 8th, 2014 36W, 2D 0.14% 0.47% -% -% 0.1% 0.6% 1.3% 2.4%
Saturday August 9th, 2014 36W, 3D 0.18% 0.62% -% -% 0.2% 0.8% 1.7% 3%
Sunday August 10th, 2014 36W, 4D 0.22% 0.82% -% -% 0.2% 1% 2.1% 3.7%
Monday August 11th, 2014 36W, 5D 0.28% 1.07% -% -% 0.3% 1.2% 2.5% 4.5%
Tuesday August 12th, 2014 36W, 6D 0.35% 1.39% -% -% 0.4% 1.5% 3.1% 5.4%
Wednesday August 13th, 2014 37W, 0D 0.44% 1.79% -% -% 0.4% 1.8% 3.8% 6.4%
Thursday August 14th, 2014 37W, 1D 0.54% 2.28% -% -% 0.6% 2.2% 4.5% 7.6%
Friday August 15th, 2014 37W, 2D 0.66% 2.87% -% -% 0.7% 2.7% 5.4% 8.9%
Saturday August 16th, 2014 37W, 3D 0.79% 3.59% -% -% 0.8% 3.2% 6.3% 10.4%
Sunday August 17th, 2014 37W, 4D 0.94% 4.46% -% -% 1% 3.8% 7.4% 11.9%
Monday August 18th, 2014 37W, 5D 1.11% 5.48% -% -% 1.2% 4.4% 8.6% 13.7%
Tuesday August 19th, 2014 37W, 6D 1.3% 6.68% -% -% 1.4% 5.2% 9.8% 15.5%
Wednesday August 20th, 2014 38W, 0D 1.5% 8.08% -% -% 1.6% 6% 11.2% 17.5%
Thursday August 21st, 2014 38W, 1D 1.71% 9.68% -% -% 1.9% 6.9% 12.7% 19.7%
Friday August 22nd, 2014 38W, 2D 1.94% 11.51% -% -% 2.2% 7.8% 14.3% 21.9%
Saturday August 23rd, 2014 38W, 3D 2.18% 13.57% -% -% 2.5% 8.8% 16% 24.2%
Sunday August 24th, 2014 38W, 4D 2.42% 15.87% -% -% 2.9% 9.9% 17.8% 26.6%
Monday August 25th, 2014 38W, 5D 2.66% 18.41% -% -% 3.3% 11.1% 19.7% 29%
Tuesday August 26th, 2014 38W, 6D 2.9% 21.19% -% -% 3.7% 12.3% 21.6% 31.5%
Wednesday August 27th, 2014 39W, 0D 3.12% 24.2% -% -% 4.1% 13.5% 23.6% 34%
Thursday August 28th, 2014 39W, 1D 3.33% 27.43% -% -% 4.6% 14.9% 25.6% 36.6%
Friday August 29th, 2014 39W, 2D 3.52% 30.85% -% -% 5.1% 16.2% 27.7% 39.2%
Saturday August 30th, 2014 39W, 3D 3.68% 34.46% -% -% 5.6% 17.6% 29.8% 41.7%
Sunday August 31st, 2014 39W, 4D 3.81% 38.21% -% -% 6.2% 19.1% 31.9% 44.2%
Monday September 1st, 2014 39W, 5D 3.91% 42.07% -% -% 6.7% 20.6% 34% 46.7%
Tuesday September 2nd, 2014 39W, 6D 3.97% 46.02% -% -% 7.4% 22.1% 36.2% 49.2%
Wednesday September 3rd, 2014 40W, 0D 3.99% 50% 8% 0% 8% 23.6% 38.3% 51.6%
Thursday September 4th, 2014 40W, 1D 3.97% 53.98% 7.9% 8% 8.6% 25.1% 40.4% 54%
Friday September 5th, 2014 40W, 2D 3.91% 57.93% 7.8% 15.9% 9.3% 26.7% 42.5% 56.2%
Saturday September 6th, 2014 40W, 3D 3.81% 61.79% 7.6% 23.6% 10% 28.2% 44.5% 58.5%
Sunday September 7th, 2014 40W, 4D 3.68% 65.54% 7.4% 31.1% 10.7% 29.8% 46.6% 60.6%
Monday September 8th, 2014 40W, 5D 3.52% 69.15% 7% 38.3% 11.4% 31.3% 48.6% 62.7%
Tuesday September 9th, 2014 40W, 6D 3.33% 72.57% 6.7% 45.1% 12.1% 32.9% 50.5% 64.7%
Wednesday September 10th, 2014 41W, 0D 3.12% 75.8% 6.2% 51.6% 12.9% 34.4% 52.4% 66.6%
Thursday September 11th, 2014 41W, 1D 2.9% 78.81% 5.8% 57.6% 13.7% 36% 54.3% 68.5%
Friday September 12th, 2014 41W, 2D 2.66% 81.59% 5.3% 63.2% 14.4% 37.5% 56.1% 70.2%
Saturday September 13th, 2014 41W, 3D 2.42% 84.13% 4.8% 68.3% 15.2% 39% 57.9% 71.9%
Sunday September 14th, 2014 41W, 4D 2.18% 86.43% 4.4% 72.9% 16.1% 40.5% 59.6% 73.5%
Monday September 15th, 2014 41W, 5D 1.94% 88.49% 3.9% 77% 16.9% 42% 61.3% 75.1%
Tuesday September 16th, 2014 41W, 6D 1.71% 90.32% 3.4% 80.6% 17.7% 43.4% 62.9% 76.4%
Wednesday September 17th, 2014 42W, 0D 1.5% 91.92% 3% 83.8% 18.6% 44.8% 64.5% 77.8%
Thursday September 18th, 2014 42W, 1D 1.3% 93.32% 2.6% 86.6% 19.5% 46.3% 65.9% 79.2%
Friday September 19th, 2014 42W, 2D 1.11% 94.52% 2.2% 89% 20.3% 47.6% 67.3% 80.5%
Saturday September 20th, 2014 42W, 3D 0.94% 95.54% 1.9% 91.1% 21.1% 48.9% 68.8% 81.6%
Sunday September 21st, 2014 42W, 4D 0.79% 96.41% 1.6% 92.8% 22% 50.1% 70.2% 82.7%
Monday September 22nd, 2014 42W, 5D 0.66% 97.13% 1.3% 94.3% 23% 51.6% 71.4% 83.6%
Tuesday September 23rd, 2014 42W, 6D 0.54% 97.72% 1.1% 95.4% 23.7% 53.1% 72.8% 84.6%
Wednesday September 24th, 2014 43W, 0D 0.44% 98.21% 0.9% 96.4% 24.6% 54.2% 73.7% 85.5%
Thursday September 25th, 2014 43W, 1D 0.35% 98.61% 0.7% 97.2% 25.2% 55.4% 74.8% 86.3%
Friday September 26th, 2014 43W, 2D 0.28% 98.93% 0.6% 97.9% 26.2% 56.1% 75.7% 87.9%
Saturday September 27th, 2014 43W, 3D 0.22% 99.18% 0.4% 98.4% 26.8% 57.3% 76.8% -%
Sunday September 28th, 2014 43W, 4D 0.18% 99.38% 0.4% 98.8% 29% 58.1% 79% -%
Monday September 29th, 2014 43W, 5D 0.14% 99.53% 0.3% 99.1% 29.8% 59.6% -% -%
Tuesday September 30th, 2014 43W, 6D 0.1% 99.65% 0.2% 99.3% 28.6% 62.9% -% -%
Wednesday October 1st, 2014 44W, 0D 0.08% 99.74% 0.2% 99.5% 30.8% -% -% -%
Thursday October 2nd, 2014 44W, 1D 0.06% 99.81% 0.1% 99.6% 31.6% -% -% -%
Friday October 3rd, 2014 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.

More tools