As we explained in the article about the first-trimester ultrasound, ultrasound scans use the ability of sound waves to pass through tissues and rebound on them depending on their density. The ultrasound then turns that bounce of sound or echo into an image that allows the specialist to make a diagnosis as accurate as possible.
During pregnancy, two types of ultrasound scans are performed: transabdominal or transvaginal. The transvaginal ultrasounds are performed during the first trimester, while transabdominal are preferred for the second and third trimesters, although sometimes they are also necessary during the first to complement the information obtained through transvaginal ultrasound.
Before going on to describe the specifications of the second-trimester ultrasound, it is important to state that, unlike X-rays, ultrasound is completely safe for both the mother and the fetus.
It is, without a doubt, one of the most important during pregnancy.
Between weeks 18 and 22 of gestation, both the size of the baby and the abundance of amniotic fluid will allow a morphological diagnosis, aimed at observing the fetal anatomy —its structure and biometry of the organs (number, location, size and shape)— in order to make sure it is growing correctly.
Purposes of the second-trimester ultrasound
Although it seems obvious, one of the primary purposes of second-trimester ultrasound is to confirm fetal life and to check the structures and development of all the baby’s organs.
This correct development will be verified through the aforementioned fetal biometry, by measuring, mainly:
- the baby’s head (biparietal diameter)
- the baby’s leg (femur length)
- the baby’s abdomen (abdominal circumference)
The baby’s anatomy will be thoroughly examined, and possible malformations will be diagnosed. However, and despite the accuracy of the new equipment, sometimes the position of the fetus or the overweight of the woman could alter the results and the prenatal diagnosis cannot be considered infallible. Also, certain malformations appear later and are not detectable in this ultrasound.
Finally, second-trimester ultrasound can also detect pathologies in the umbilical cord, the placenta and the amniotic fluid.
We hope this article has been useful for you. You will find further information at the website of the Unidad de la Mujer. You can also contact us at the number (+34) 917 303 673