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All Woman
The benefits of ultrasounds
Donna Hussey- Whyte
Monday, March 16, 2009
OBSTETRIC sonography (ultrasonography) is the application of ultrasound to visualise the embryo or foetus in its mother's uterus (womb) and is often a standard part of prenatal care.
Ultrasounds can detect a variety of information regarding the health of the mother and the foetus, as well as the progress of the pregnancy and to detect developmental defects before birth.
Gynaecologist, Dr Wesley Bernard, from the Nuttall Medical Centre, says a standard ultrasound should be done during the first trimester (14 weeks) in order to determine the date of delivery.
"The doctor can work out the date of delivery based on the ovulation date given by the mother, but she may have miscalculated so the ultrasound will detect the correct date," Dr Bernard said.
He said based on the normalcy of the first ultrasound, there may be no need for another during the pregnancy.
However at 20 to 26 weeks' gestation, an ultrasound can determine certain types of abnormalities with the foetus. This includes abnormalities of the brain.
Many of these abnormalities can be fixed in the womb, but unfortunately, none of these procedures are done in Jamaica.
One of the most common types of abnormalities detected in Jamaica, which can be fixed in the womb, is spina bifida (opening in the spinal cord).
Ultrasounds include checking the status of the limbs and vital organs, as well as (sometimes) specific tests for abnormalities. Some abnormalities detected by ultrasound can be addressed by medical treatment in utero, though indications of other abnormalities can lead to a decision regarding abortion.
Ultrasounds may also detect foetal organ anomaly. Usually scans for this type of detection are done around 18 to 20 weeks of gestational age.
"If patients have bleeding during pregnancy, it is necessary to do an ultrasound," Dr Bernard warns. "The ultrasound will determine the position of the placenta whether or not it is too low. In this case the woman may need to do more than one ultrasounds for this."
The gestational sac can sometimes be visualised as early as four and a half weeks of gestation (approximately two and a half weeks after ovulation) and the yolk sac at about five weeks gestation. The embryo can be observed and measured by about five and a half weeks. The heartbeat may be seen as early as six weeks, and is usually visible by seven weeks gestation.
The sex of the baby can usually be determined by ultrasound at 20 weeks' gestation. This is also the best time to have an ultrasound done as most infants are the same size at this stage of development.
Depending on the skill of the sonographer, ultrasounds may suffer from a high rate of false negatives and false positives, which means care has to be taken in interpreting the accuracy of the scan.
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