February 16, 2019

Do I get an ultrasound in my third trimester? The function of ultrasound in late pregnancy.

For many expectant parents, the first comment after seeing their baby onscreen in a detailed ultrasound for the first time is, “when do I get to SEE my baby again?”. This is a natural question- after all, ultrasound is a wonderful way for parents and family to get to know  and bond with a baby before the Birth day. However, ultrasound is a medical procedure and has limited use in the last few weeks of pregnancy.

Most women who have gotten prenatal care from an early stage of pregnancy get to see their babies at least once in the first trimester for a dating ultrasound and again for a genetic screening for down’s syndrome, if needed. In the second trimester of pregnancy, ultrasound is used to look at at the anatomy of the baby, make sure all the parts are there and functioning, and to look at the placenta, umbilical cord, and blood flow to the uterus. From a medical perspective, it is this ultrasound that really determines if the fetus is developing normally.

In the third trimester, ultrasound can be used to look at the health and functioning of the placenta and umbilical cord and to evaluate the baby’s growth. Unfortunately, the accuracy of ultrasound at predicting a baby’s weight diminishes later in the pregnancy so that an ultrasound can over or underestimate the weight by a pound. Late pregnancy ultrasound is essential for high risk pregnancies with conditions such as diabetes, high blood pressure, high or low amniotic fluid, and some twins. For most low risk pregnancies, ultrasound is mostly needed at the end if a baby is suspected of growing too much or not enough or if the baby isn’t moving as much as usual.

In conclusion, ultrasound is a vital and exciting tool during pregnancy. While it is most helpful at providing information about a fetus early in pregnancy, it can also be useful in selected pregnancies during the third trimester. Because there is no guarantee that ultrasound will be needed later in pregnancy, it is best to really enjoy and savor the second trimester ultrasound and to make sure and grab some good shots to start the baby album. We offer both early and late ultrasound in our Mesa ob gyn office.

Tamar Gottfried is a Board Certified Obstetrician/ gynecologist  practicing  general Ob/gyn in Mesa Arizona and affiliated with Banner Desert and Banner Gateway Medical Centers. She can be contacted at 480-545-0059. This is a general interest article only and is not intended to be medical advice. See a medical professional before making medical decisions





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