Does the position of the placenta in the uterus enable you to determine
the sex of a fetus? How do you determine the position of the placenta? Stay tuned
The point where an embryo implants will determine the position of the placenta
in the uterus. Early in a pregnancy when the size of the placenta is small,
there are 5 possible locations for a placenta. Right, left, anterior, posterior, and top. Later
in pregnancy the placenta grows larger so it can cover two or three locations at the same time.
Using ultrasound, the uterus can be seen and the placenta can be identified in the uterus. Most
of the time, this is a straightforward procedure. However, the uterus doesn't
always look the way it looks in the text books. Sometimes, the uterus can be flipped forward,
sometimes it can be flipped back. It can also be rotated clockwise or counterclockwise.
Is it possible to determine the genetic sex of a fetus by looking at the position of the placenta
in the uterus? Seems unlikely. The first question I had is why this would happen. Is one side of
the uterus better for a male or female embryo? Not likely. The uterus is symmetrical. That means that
the left and right side are the same. The anterior and posterior are the same. Embryo implantation is
one of the earliest events in pregnancy. It occurs several days after ovulation when the embryo is a
blastocyst. There are no known differences between male and female embryos at that point so how,
exactly, would this amazing phenomenon occur? Does the uterus pull embryos of a certain sex
to one side? Or does the embryo of a certain sex migrate in the uterus to find a location that it
likes? Or does the embryo implant anywhere but embryos of one sex are miscarried from
one side and embryos from the other sex are miscarrying from the opposite side?
Well, what does the scientific data say? I found three small studies on this topic. In
these studies, an ultrasound was performed during the 1st trimester. They then waited until birth
to determine the apparent sex of the baby. Study number 1 said that about 70% of the male babies
came from a right sided placenta and 70% of the females came from the left. Anterior and posterior
did not matter. Study #2 found that about 70% of the girls had an anterior placenta. Right and side
and left side did not matter. Exactly the opposite of the first study. It was also
very suspicious that there were no instances in which the location of the placenta was not clearly
on one side or the other. Study #3 which was the largest study of the three. This study seems the
best quality study. For example, they reported that in about one third of the ultrasounds,
the location of the placenta was not clearly one side or the other. This study did not
find any relationship between the location of the placenta and the sex of the fetus.
Our Infertility TV bottom line is this. There is no scientific reason for the location of the
placenta to be different based on the sex of an embryo when it implants. Furthermore, there is no
consistent high quality evidence that the location of the placenta will predict the sex of a baby
when born. Whatever the location of the placenta, you re likely to be correct about 50% of the time