Pregnancy Due Date.

Say What

What is my due date?

Your “due date”, also known as your EDC(estimated date of confinement) or EDD(estimated date of delivery) is the gestational age at which the onset of labor is expected to spontaneously occur. In weeks gestation, this is usually the 40 week mark.

While there are numerous ways to arrive at the EDC/EDD, Naegele’s rule remains a personal favorite!

Naegele’s rule states that we can determine the due date by adding a year, subtracting 3 months, and adding 7 days to the first day of a woman’s last menstrual period. For example, lets say your last menstrual period was October 10, 2014. According to Naegele’s rule, your due date would be July 17, 2015.

Though Naegele’s rule is a bit “old school” by most standards, I LOVE OLD SCHOOL! It’s a quick and easy way for me to approximate a due date being that when I initially see patient’s for an establish pregnancy or a new obstetric visit, the couple is soooo excited about the pregnancy that the first question I’m usually asked is, “WHEN’S THE DUE DATE”?!?!

While I just mentioned a quick and easy way to determine the due date, when I see patient’s for an establish pregnancy visit, the main purpose of said visit is for me to determine, not only a due date, but also how far along into the pregnancy the patient currently is. This is most commonly accomplished by obtaining an ultrasound measurement known as a crown-rump length.

A crown rump length is a measurement typically obtained by transvaginal ultrasound and looks at the distance between the crown or head, and the rump or buttocks of the fetus.

In my practice, in a woman with a known last menstrual period, we typically use the due date determined by the last menstrual period; the crown-rump length measurement is used more for confirmatory purposes.

If, however, there is more than a week’s discrepancy; i.e., seven day difference between the date obtained by using the last menstrual period and that obtained using the crown-rump length, we go with the dating determined using the crown-rump length. Got it? Hoping I didn’t lose you on that one…..

More simply put, as long as the dating is congruent, we use the dating obtained by last menstrual period; if there is more than a 7 day discrepancy in the dating obtained by the aforementioned methods, we go with the dating determined by using the crown-rump length measurement.

Hoping this blog post adds value to your day!

Until Next Time,

Look Better. Feel Better. Be Better.

Dr. Angela

About Dr. Angela

Mother, Midwesterner, and award-winning OB/GYN, Dr. Angela is equal parts best girlfriend and bold professional, supporting women’s health with innovative approaches to care and heavy doses of humor. Dr. Angela has done more than launch a successful practice, she has defined herself as a voice for a new generation of womanhood, established her ASK DR. ANGELA brand committed to authenticity, and built a community rooted in trust, candor, and compassion.


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