Medically reviewed by
Ultrasounds can help you get a better understanding of your pregnancy and baby's health, as well as determine how far along you are in your pregnancy. Ultrasound is also used to measure the growth of your baby and ensure that he or she is growing as expected throughout this period. Ultrasounds are safe for both mother and child, with no evidence of negative effects.
In this article, we will explore the routine ultrasounds you may receive during your pregnancy.
A dating ultrasound is usually done in the first trimester between seven and 10 weeks of pregnancy. This is a routine ultrasound that is done to determine the gestational age of the fetus, determine an expected due date, and set a baseline for your baby’s growth. A dating ultrasound is the most accurate means to establish gestational age.
Using a transvaginal ultrasound probe, the ultrasound technician will measure the baby’s crown to rump length, measure their heart rate, and assess overall fetal health.
Between weeks 11 and 14 of your pregnancy, your provider may refer you for a nuchal translucency ultrasound. This scan measures the fluid-filled space at the back of your baby’s neck. This measurement can help determine and estimate the risk of the fetus having a chromosomal abnormality such as Down syndrome or Turner syndrome.
The chances of chromosomal abnormalities in pregnancy increase as you age, however, anyone can have a baby with chromosomal abnormalities, so this scan is routinely offered to pregnant parents.
The nuchal translucency ultrasound can be performed transvaginally or abdominally. The sonographer will determine the best method for you based on your body and gestational age.
The anatomy scan is a detailed ultrasound that looks at the baby's body and growth halfway through your pregnancy between 18-22 weeks. This scan is most commonly performed using transabdominal ultrasound, which means scanning through your lower abdomen.
Your anatomy scan is a comprehensive examination of the development of your baby’s bones, heart, brain, spinal cord, face, kidneys, and abdomen. The scan can also detect certain congenital abnormalities. In most cases, you can also learn the sex of your baby if you’d like.
The third trimester is a time of rapid fetal growth, with an average weight gain of about 1.5 lbs per week. After 27 weeks, your doctor may want to check on the health and development of your baby with a third-trimester ultrasound. This will help them assess any growth disorders that may be present, determine the baby’s presentation (how your baby is positioned), characterize the placenta and amniotic fluid (the fluid surrounding the baby in utero), and check the blood flow patterns in the umbilical cord, brain, and liver vein.
Measurements in ultrasound are precise, but the estimated weight given at the third-trimester scan can differ from the baby's true size by a pound in either direction. Research shows this stems from the fact that two babies of identical size can have differing weights (up to 1.1 lbs). Additional factors can widen the margin of error, such as the amount of time between the ultrasound and birth, and your baby’s individual growth rate, among other factors.
They allow care providers to detect and address issues as early as possible, which can help moms and babies have better outcomes.