During pregnancy, 3 ultrasounds are required, one in each trimester.

Currently, it is recommended to perform genetic screening ultrasound or nuchal translucency, which is performed between 12 and 14 weeks of gestation. This evaluates the risk that each mother has of a chromosomal disease, risk of preeclampsia, intrauterine growth retardation and preterm birth. This ultrasound is part of the mandatory health plan, however, it is often restricted to high-risk patients.

Between 12 and 14 weeks, fetal sex can be determined by 70 - 95%, however, the total development of the fetal genitalia occurs between 16 and 18 weeks.

The second trimester ultrasound seeks to evaluate the already developed fetus and rule out possible malformations or abnormalities.

The last ultrasound or the third trimester ultrasound is basically to evaluate fetal growth to prepare for delivery.

3D or 4D ultrasound is not necessary and is used solely for recreational purposes, in an attempt to show the face of the new being in a photograph that will be a nice memory.

The prenatal doctor will determine if it is necessary to perform obstetric ultrasounds
additional. This will depend on the gain in centimeters of the maternal belly and, if there is any additional risk factor for the fetus to have inadequate weight gain, as occurs in patients with hypertension and gestational diabetes.