Estimate by Birth Date 

* Please note: This is only an estimate based on averages.

Using Mittendorf’s Observations of Gestational Term.

•  288 days from conception to Birth.
•  Assumes white (add 5 days to the calculated conception date for non-white).
•  Assumes mother's 1st pregnancy (add 5 days to the calculated conception date if it is NOT the mothers 1st  pregnancy).
•  Assumes single birth (add 4 weeks to the calculated conception date for each additional baby).

Individual's Birth Date:              
                                         (MM/DD/YYYY format)


 

Estimated Conception Date:       

What is the "normal gestational term" for humans?

Mittendorf’s Observations of Gestational Term. In the 1980’s, Mittendorf noticed that birth dates for women in his practice, primarily second-generation Irish-Americans, averaged seven days past their “due dates”. He reviewed his records, then went on to review records of 17,000 births, and determined the average healthy, white, private-care, primiparous woman averaged 288 days from LMP to birth: 8 days longer than Naegele’s rule. Mittendorf and other researchers have further determined several factors that affect gestational term, including ethnicity, parity, nutrition, substance use, mother’s age, and mother’s size. Based on Mittendorf’s data, a more appropriate formula might be:

(LMP – 3 months) + 15* Days = Due Date

* Add 10, rather than 15, if mother is non-white, or multiparous

Normal Variations in Gestational Term:

From the wide range in birth dates, it is clear that some variation is normal. Some examples of known variations: Multiparous women average 283 days, versus the 288 days of primiparous women. (Mittendorf)  Black women averaged 8.5 days fewer than white women of similar socioeconomic status. (Mittendorf) Other studies indicate that for multiple births, each additional baby in the uterus shortens the pregnancy by 4 weeks on average.