Obstetric ultrasound uses sound waves to develop images of an unborn baby. To generate the picture, sound waves of high frequency ranging from 3.5 MHz to 7 MHz are used. The high waves are generated by a transducer which is placed on the mother’s abdomen. It works like a torch that reveals the internal content of the uterus. Ultrasound uses a real time scanner and it can develop moving picture of the fetus on a TV monitor. Introduced in 1950s, it was later used as a tool for scanning pregnancy.
Sonography is used for the assessment of the fetal size and gestational age. The measurement of gestational age is based on the crown rump length, the Biparietal diameter, the femur length, and the abdominal circumference. The viability scan of the fetus is done about 6 to 10 weeks of the pregnancy. Pulse Doppler ultrasound is used to measure the heart beat and it confirms continued pregnancy by 95%.
The location of pregnancy can be determined by sonography. There are two types of locations: intrauterine and ectopic. Intrauterine pregnancy refers to the condition when the pregnancy is within the uterus. If the pregnancy is implanted outside the uterine cavity, it’s called ectopic pregnancy. The site of the placenta and the lower edges of the placenta can be determined using ultrasound. An assessment of cervix can be made. For instance, a short cervix indicates preterm and therefore, extra caution may be required to reduce the risk. Multiple pregnancies can be determined by examining the number of fetuses by using ultrasound. It also provides data related to the fetal growth, fetal anomaly, and placental abnormalities.
Ultrasound before 20th week can be used to determine structural abnormalities in the fetus. Certain medical conditions such as hydrocephalus, myelomeningocoele, anencephaly, Gastroschisis, and fetal hydrops can be examined using ultrasound. Problems of cleft lips and congenital cardiac abnormalities can also be diagnosed in the early stages. The growth of fetus can be recorded in various stages using ultrasound. It helps in the diagnosis of intrauterine growth retardation (IUGR), a condition in which the birth weight is below ten percentile of the gestational age. In such cases, it means that the fetus fails to achieve the possible genetically determined size.
Fetal heart starts beating on the 23rd day after conception but it can vary in the gestational age. Normal heart beat is measured in the 6th week. The human embryo can move its back and neck in the sixth week but fetal movement is not reflexive in the initial stages. The movement in legs and arms can be detected through ultrasound in the 7th week of pregnancy. The sex of the fetus can be determined in the 16th week of pregnancy but there must be extra care to ensure an accurate scan.
The use of ultrasound in pregnancy is almost a standard procedure in modern hospitals. It’s very useful for expecting parents who want know more about the unborn baby.
Follow these links to learn more about ultrasound and pregnancy.