Trying to determine what gender a fetus is can be stressful for many parents. Although some parents prefer for the baby's gender to be a surprise at birth, others prefer to know it in advance so they can begin to think of the unborn child as a boy or a girl. One of the difficulties with this, however, is that ultrasound testing can sometimes be incorrect.
Identification
Ultrasound uses high frequency sound waves to examine soft tissue structures, which includes the developing fetus. The sound waves bounce off structures and are reflected back where they are absorbed by a detector. These sound waves are then processed by a computer to develop an image that can be used to, among other things, determine a baby's gender.
Typical Gender Determination
Although an ultrasound can determine gender in either the first, second, or third trimesters, it is usually checked during the 20th week of gestation. This is because doctors typically schedule the ultrasound around this time to monitor the fetus' growth and to make sure that the baby and the uterus are healthy. In addition to using the ultrasound to check the baby's development and to ensure that there are no abnormalities in the uterus, the ultrasound technician can also determine the baby's gender at the parents' request.
Accuracy Timeline
According to a study done in Brazil, the United Kingdom and Israel, gender can be ascertained via ultrasound with high accuracy as early as at the 12-week mark. This study looked at the effectiveness of determining gender by looking at the angle of the "genital tubercle" (the precursor to the genitals) at 11, 12, 13, and 14 weeks. This study found that at 12 weeks this technique could accurately predict the baby's gender 84 percent of the time (compared to at 11 weeks when the accuracy was at 50 percent).
Factors That Influence Accuracy
The time at which a fetus' gender can be accurately determined depends on a number of factors. The type of ultrasound can affect when gender can be determined (3-D ultrasound provides three dimensional images and 4-D ultrasound provides three dimensional images over time). The position of the fetus is another important aspect; if the fetus has its legs crossed or is in a position that hides the genitals, the gender cannot be determined. Finally, the skill of the technician plays a role. A more-experienced ultrasound technician may be able to determine the fetus' gender earlier than a less experienced technician. According to several studies summarized by Consumergenetics.com, accuracy in correctly predicting if the baby is a male or a female varies depending on where the ultrasound is performed. In one of the studies, reported in 2005, a prediction of a female is more likely to be correct than a prediction of a male.
Amniocentesis
Amniocentesis is another way of determining gender, and according to Pregnancy-info.net, it is also the most accurate method. With amniocentesis, some of the amniotic fluid that surrounds the infant is extracted and analyzed. Because this fluid contains some cells from the fetus, physicians can look for the presence or absence of the Y chromosome (which, when present, causes a person to be male).
