Ultrasound Series: Part 4 Begin Small

August 2, 2021

As a nurse, I have always thought of my job as purely medical. Performing tests, doing physical assessments, carrying out doctors’ orders – to name some of my obvious responsibilities. Never in my wildest dreams would I have added “blogger” to that list. Writing a blog was something that “creative” people did. I’m a nurse, I like facts. To prepare for this new job responsibility, I researched how to write. Some of this research suggested that I “begin small”. Many of the best things in life begin small: written articles, gardens, people, etc…

As a nurse trained in limited obstetric ultrasound, I can identify with the word “small”. Part of what I do is to measure the baby to find out its gestational age and thus a due date. Many women do not keep track of their menstrual cycles and they have no idea how far they could be.  Ultrasound can answer that question. 

As with everything growing, the younger the baby is, the smaller it is. In the first trimester (0-13 weeks), the baby is measured by using a CRL (crown-rump length), this is accomplished by measuring from the top of the baby’s head to the end of the baby’s bottom. Last week, I measured a baby that measured 6 weeks and 1 day gestational age. The length was less than half a centimeter! This size looks like a diamond ring on the ultrasound, with the yolk sac being the ring and the baby and heartbeat the diamond. To me, a diamond ring represents the promise of a beautiful life spent with someone that you love. This ultrasound picture represents the same promise–a beautiful life spent with someone that you love.

Babies grow very quickly at this point in your pregnancy, going from 0.40 centimeters at 6 weeks gestational age to around 6 centimeters at 12 weeks gestational age. 1

After 14 weeks gestation, babies are too mobile (they like to stretch) to continue measuring in this manner. In our clinics, we will utilize a BPD (biparietal diameter) and an FL (femur length) at this time. A BPD is a measurement of a cross-section of a certain area on the baby’s head (different landmarks are utilized to make sure that the measurement is at the correct location and angle). A “femur length” is a measurement of the baby’s thigh bone. 

When a woman is early in her pregnancy, it can sometimes feel a little abstract in that she can’t feel any movement yet; she hasn’t visibly started “showing” yet; she hasn’t started with any of the usual symptoms of pregnancy. It doesn’t feel “real”. During the ultrasound, if I have a baby model of correlating age, I will place the model on the mother’s abdomen in the position that the baby is inside the uterus. These baby models accurately depict the size, weight, and development of the baby that she’s carrying and gives her a more realistic picture of her pregnancy. 

Knowing the gestational age of your baby is especially important in today’s world where the “abortion pill” is becoming easier than ever to obtain and utilize. Medical guidelines dictate that the RU-486 should be taken prior to 10 weeks gestational age, but that topic (the abortion pill) will be reviewed in my next blog.