Nursing Student
New Grad

02.01 Gestation

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  1. Gestation refers to the time period of carrying the pregnancy
  2. Nägele’s Rule is used to estimate date of delivery
  3. It is also estimated by ultrasound measurement

Nursing Points


  1. Gestation is around 40 weeks long
  2. Estimation of due date is most accurate if ovulation day is known
  3. Nägele’s Rule is most accurate for the patient that has normal 28-day menstrual cycle
  4. Ultrasound (U/S) can be used in early pregnancy to measure the gestational age of the fetus
    1. Crown to rump length
    2. Can be off by 7-10 days


  1. Nägele’s Rule
    1. Find out when the last menstrual period happened (LMP)
    2. Subtract 3 months, Add 7 days to the first day of the last period, add a year
    3. Add 7 days to the first day of the last period, then count ahead 9 months
  2. Obtain measurement of embryo length to estimate gestational age
    1. Position woman comfortably on U/S table
    2. Transvaginal or external U/S performed

Therapeutic Management

  1. No medical treatment is necessary.
  2. Comfort can be offered in explaining transvaginal ultrasound to ease the patient’s mind since this is intrusive.

Nursing Concepts

  1. Human Development
  2. Reproduction

Patient Education

  1. Educate on what due date is calculated and give necessary pregnancy education

Reference Links

Study Tools

Video Transcript

Okay guys, in this lesson, we’re going to talk about gestation. Let’s talk about the basics first. Gestation refers to the time period of carrying pregnancy so that is when we say, “How many weeks is she/you?”. A pregnancy is 40 weeks longs. Now we have to be able to figure out how far someone is in gestation. One of the ways is to do Nägele’s Rule. This is a little math equation and is most accurate on someone that has a normal 28 day cycle. It is done by asking the pating the first day of her last menstrual cycle. We take that day and subtract 3 months, add 7 days, add a year. So for example December 1st 2018 was the first day of the last cycle. We subtract 3 months which would be September 1, 2018. We add 7 days, which is September 8th, 2018 and then add 1 year. This is September 8, 2019. So what happens in cases where the patient is irregular or doesn’t know when her last cycle started. With this a ultrasound can be done. The crown to rump or head to bottom is measured. This measurement will give an estimated gestion of the fetus. This can be off by 7-10 days and this is because it all depends on when implantation has actually occurred.

Let’s compare the two ways to obtain the gestational age. So for Nägele’s again we subtract 3 months from the last menstrual period, add 7 days, and add 1 year. Keep in mind if this patient’s last menstrual period was in January then you have to pay careful attention to subtracting the year with it and re-adding or you will end up with someone being pregnant for 2 years and that wouldn’t be right. This could be tricky on a test so make sure to subtract the year so it does not mess you up. With an ultrasound the patient should be comfortable at an incline and the ultrasound will either be external or internal depending on how far along they believe the patient to be.. Usually if they are 6-11 weeks it will be internal because the fetus is so small.

There is not medical management necessary. It is important to help explain to the patient what we are doing with ultrasound. An external ultrasound is not as intrusive but a transvaginal can be intrusive so we want to educate on the process and ease any discomforts. It will be important to educate on why we are calculating the due date and what it means. We should also educate on the importance of coming back for future prenatal appointments and caring for herself during pregnancy.

Pregnancy gestation deals with human development so this is a nursing concept and pregnancy had to deal with reproduction so this is another concept.
Let’s review our key points. Length of pregnancy is what gestation is referring to. Nägele’s rule is done to estimate the due date. Again we ask the last menstrual cycle started, subtract 3 months, add 7 days, add a year. Ultrasound will either be transvaginal or external. This will be done to get a measurement of the embryo/fetus from crown to rump length. This measurement will determine the gestational age.

Make sure you check out the resources attached to this lesson. Now, go out and be your best selves today. And, as always, happy nursing.