Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Because of the capability of ultrasound to be able to make images on the item being scanned, this technology has been applied in medicine.

Pregnancy Ultrasound scans is one of the manifestations of this technology. This is being used to determine the health conditions of the baby in the womb.

Pregnancy scans although may have the same purposes and results, pregnancy ultrasound has several varieties. This depends on the process used to do the ultrasound.

Transvaginal ultrasound is the traditional means of doing pregnancy scans. This is done by placing a transducer in the woman's vagina. A transducer is a probe that emits high frequency waves to determine the condition of the fetus in the womb.

Transvaginal ultrasound is being used for women who are obese and also in scanning in early pregnancies. The transvaginal ultrasound has been very effective in diagnosis of ectopic pregnancy.

On the otherhand, there is another procedure in doing pregnancy scans. This is used to used to evaluate the pulsations in the fetal heart and bloods vessels for signs of abnormalities. Such ultrasound is called Doppler ultrasound.

Doppler ultrasound is used to examine the progression of the well being of the baby inside the womb and also in diagnosis of cardiac malformations.

Obstetric sonography (ultrasonography) is the application of medical ultrasonography to obstetrics, in whichultrasoundscans is used to visualize the embryo or fetus in its mother's uterus (womb). The procedure is often a standard part of prenatal care, as it yields a variety of information regarding the health of the mother and of the fetus, as well as regarding the progress of the pregnancy.

-- wikipedia

Pregnancy scans ultrasound is being done by placing a transducer at the abdomen. To be able to see the images clearly, gel is spread at the abdomen. This way the radiation is spread in an effective manner resulting to a more concise image and movement of the fetus.

4d scans is like the 3d scan only that the fetal movements could be monitored. Because the procedure rapidly capture the image, it produces the 4d baby ultrasound scans.

Here is a guide from pregnancy-and-baby-ultrasoundscan.co.uk on when and why should you have your pregnancy scans at a specific time interval during your pregnancy.

When to have a Scan

Scans may be performed in the First Trimester to:

• Confirm a normal pregnancy
• Confirm viability
• Assess the baby's age (gestation)
• Assess potential problems such as threatened miscarriage, ectopic pregnancy etc.
• Assess the baby's heartbeat
• Confirm number of embryos/fetuses
• Identify any abnormalities of the placenta, uterus, and other pelvic structures

In the Second Trimester (after 13 weeks)

• Assess the baby's age, growth, position, and sometimes gender.
• A detailed look at the baby’s vital organs and limbs to identify or rule out any possible congenital problems.
• Identify any developmental (growth) problems
• Rule out multiple pregnancies
• Evaluate the placenta, amniotic fluid, and other pelvic organs.

In the Third Trimester (after 26 weeks): Scans not normally required at this stage except when monitoring pregnancy development and fetal wellbeing in special situations: these may include:

• Multiple pregnancy
• Suspected fetal growth problems
• Chronic medical conditions such as diabetes, hypertension, epilepsy etc.
• Pre-eclampsia Other situations where a scan may be called for are when there is a need to:
• Detect cervical changes that might predict preterm labour.
• Verify breech presentation or other uncommon fetal or cord position before delivery.
• Get valuable information leading to treatment of any conditions arising in the course of a pregnancy in a bid to improve a woman’s chances of having a healthy baby.