it a boy or a girl? This is one of the first questions asked
by a new mom-to-be. Until recently, the ultrasound was the
only non-invasive, scientific way to learn the gender of the
unborn baby. Other highly accurate methods such as chorionic
villus sampling (CVS) and amniocentesis (“amnio”)
are invasive, carry a risk to the mom and/or baby and are
only prescribed by a doctor for older moms or for pregnancies
with risk of genetic disorders.
The Pink or Blue® test is a new, non-invasive DNA-based
gender test based on detecting small amounts of the baby’s
DNA in the expectant mother’s blood. If small amounts
of the Y-chromosome are detected, then the baby is a boy.
If no significant amount of Y-chromosomal DNA is detected
then the mom is expecting a baby girl.
Many questions arise about ultrasounds and gender
1. How early can an ultrasound scan show the gender of the
2. How accurate is the gender prediction from an ultrasound?
Before we can answer those questions, we must first understand
what an ultrasound is.
What is an ultrasound?
An ultrasound (also called sonogram) scan uses high frequency,
low power, sound waves sent through the mom’s belly
into the uterus. As these energy waves encounter internal
surfaces (uterus, placenta, fetus) they bounce back and are
detected by the scanner. The amount of ultrasound waves bouncing
back varies as the surface which they hit changes e.g. folds,
texture, and density. The computer monitor uses this information
to generate a picture of the fetus and its environment which
can be viewed on the monitor.
The ultrasound image can be used to measure the size of the
baby to assess its development and growth. The ultrasound
is used to detect certain fetal developmental abnormalities
such as cleft palate, Down Syndrome, spina bifida, cardiac
anomalies, and other physical malformations.
Ultrasound and Gender Detection
Gender is determined by visually inspecting the ultrasound
image for the genital tubercle (developing reproductive tissues)
in the first trimester, or penis/labial folds in later stages
of pregnancy. The accuracy of this method of gender determination
depends on the position of the baby as well as the skill of
the technician performing the scan. Several studies have been
conducted to determine the accuracy of gender prediction at
different stages of pregnancy.
Here are brief summaries of a few of these studies:
Michailidis et. al. “The use of three-dimensional
ultrasound for fetal gender determination in the first trimester.”
Br J Radiol. 2003
- Study included 200 participants in the first trimester;
2 technicians independently reviewed the ultrasound data
to determine gender
- gender was determined in 81.5% of participants (18.5%
- In cases where both examiners agreed on gender determination,
they were 85.3% accurate.
- Of the 14.7% error rate: 6.7% were cases where both examiners
predicted the incorrect gender, and 8% were cases where
one of the examiners predicted the wrong gender.
Adeyinka et. al. “Ultrasonographic assessment
of fetal gender” Afr J Med Med Sci. 2005.
- Study included 415 participants ranging from 15-40 weeks
- Gender was determined in 87.5% of participants (12.5%
- 90.6% of female predictions were correct while 83.2%
of male predictions were correct
Efrat et. al. “Fetal gender assignment by first-trimester
ultrasound.” Ultrasound in Obstetrics and Gynecology.
- Study included 656 participants ranging from 12-14 weeks
- Gender was determined in 93% of participants (7% inconclusive
- At 12 weeks, 99% of male gender predictions were correct,
and 91% of female predictions were correct
- At 14 weeks, 100% of both male and female predictions
Hsiao et. al. “Fetal gender screening by ultrasound
at 11 to 13(+6) weeks.” Acta Obstet Gynecol Scand. 2008
- Study included 496 participants who were 11-14 weeks gestation
- Gender was determined in 89% of participants (11% inconclusive
- A t 11 weeks gestation, gender predictions were 71.9%
accurate, at 12 weeks accuracy was 92%, while at 13 weeks
the accuracy increased to 98.3%
The results of these and other studies vary greatly, and
no general consensus exists on an overall accuracy rate for
ultrasound gender detection. The inconclusive rate for gender
determination is also quite high. Many message boards can
be found online with confused expectant moms who try to read
each other’s ultrasounds after a technician was hesitant
to assign a gender to the fetus. Many messages can also be
found from women who received conflicting ultrasound results
on subsequent visits, or found out in the delivery room that
multiple ultrasounds had been wrong.
It is important to go into an ultrasound with proper expectations.
The real usefulness of the ultrasound is in determining the
overall health of development of the baby. The gender prediction
made at an ultrasound scan, especially one performed early
in the pregnancy, should not be assumed to be 100% correct.
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