Ultrasound is an imaging technique that uses sound waves (similar to radar) and is commonly used in medicine. During pregnancy, three ultrasound examinations are performed to monitor the development of the fetus. Ultrasounds are conducted in medical offices by ultrasound physicians who have sufficient experience to detect any medical risks. It's often during the first ultrasound that prospective parents fully realize the pregnancy.
How Ultrasound Works
During an ultrasound, the patient lies down. The ultrasound physician applies a transparent gel that acts as a conductor for the sound waves, improving their passage for better interpretation. Ultrasound is a painless technique and has no known side effects on the health of the fetus. However, as a precautionary measure, it is recommended not to overuse ultrasounds unless necessary. Artistic and commercial ultrasounds, which are performed solely for entertaining pregnancy images, are discouraged.
The First Ultrasound
This typically occurs between the 10th and 12th week of pregnancy. It is used to determine the number of embryos and accurately date the pregnancy. Several criteria are evaluated to detect possible anomalies: the closure of the skull and abdomen, the number of limbs, the thickness of the neck (abnormal thickness may indicate a genetic disorder), and the appearance and position of the placenta.
The Second Ultrasound
Also known as the morphological ultrasound, it takes place between the 20th and 22nd weeks of pregnancy. It allows for a more detailed study of the fetus's development. All vital organs (heart, kidneys, liver, lungs, brain) and limbs are visualized, measured, and compared to reference data (skull, femur, arms, legs, number of fingers and toes, skeletal elements). The ultrasound physician conducting the examination evaluates the quality of exchanges between the fetus and the mother (oxygenation and nutrient transfer), the volume of amniotic fluid, and the placenta. It is usually during this second ultrasound that the baby's sex can be revealed.
The Third Ultrasound
It takes place between the 30th and 32nd weeks of pregnancy. It assesses the fetus's growth: weight, size, and development of vital organs. Some anomalies may only be visible at this stage. The ultrasound physician checks that everything is ready for birth: the fetus's position, the placenta's position, and the umbilical cord. This information, systematically transmitted to the healthcare professional monitoring the pregnancy, is invaluable for childbirth preparation (especially if the baby has not turned and still retains a head-up position, which may indicate a breech presentation, for example).