The placenta is the organ that transfers oxygen and nutrients from the mother’s blood to the baby’s blood. It is connected to the mother’s uterus on a large surface. The baby is connected to the mother’s placenta via the umbilical cord. The placenta can be located anywhere on the surface of the uterus. What matters most is where the lower edge of the placenta extends because if it is too low in the uterus it can cause bleeding and prevent the fetal head from descending during labor.
The location of the placenta can change during pregnancy for a number of reasons, as follows:
- By mid-gestation, the placenta occupies 50% of the uterine surface. By 40 weeks of gestation, the placenta occupies only 17-25% of the uterine surface. It does not shrink, but the rest of the pregnancy grows more, and the uterine surface expands.
- In the third trimester the baby’s head begins to descend into the pelvis in preparation for labor. The pressure of the fetal head on the lower part of the uterus (the lower uterine segment) causes it to stretch and lose weight. The site of placental attachment then appears to increase.
For these reasons, many pregnancies have a low placenta at 18-20 weeks gestation, but do not have a low placenta at the end of pregnancy.
If the placenta remains low, it is called ; placenta previa;. If the placenta completely covers the cervix, then there is no way that the baby can give birth vaginally without causing massive bleeding from the mother and baby. In this situation, caesarean section is the only sure way to deliver the baby.
For the rest, as for the positions of the placenta, whether it is located in the back or front, it does not mean anything in particular. However, parents often have questions about the position of the placenta, the correlation between the placenta and the sex of the baby, the best position for a normal birth and so on. Let’s try to give an answer to the most frequently asked questions and doubts.
What is the posterior placenta?
The term posterior placenta describes the attachment of the placenta to the posterior wall of the uterus.
If the ultrasound shows that you have a posterior placenta, you don’t have to worry. This is completely normal. The upper (or fundamental) portion of the posterior wall of the uterus is one of the best locations where the fetus is located. It allows them to move to the anterior position just before birth.
In addition, a posterior placenta does not affect or interfere with the growth and development of the fetus.
Does having posterior placenta mean you’re going to have a boy?
There is no evidence that the location of the placenta affects or is indicative of the sex of the unborn child. On this topic there are many theories and even some limited studies, but more research is needed to really find a link (if it exists) between the sex of the baby and the position of the placanta. The best way to find out your baby’s sex is if it can be seen on an ultrasound or if you included it in any blood tests you did early in pregnancy.
Is the posterior placenta normal?
Yes, a posterior placenta is completely normal and should not be a cause for concern. Some believe that expectant mothers may feel a stronger movement of the baby when the placenta is in their back area, but there is not much concrete evidence to support this.
Posterior placenta and preterm delivery
None of the national or international obstetric guidelines confirm the results of a study that found that the posterior placenta increases the risk of preterm delivery and an anterior placenta increases the risk of pregnancy-induced hypertension, gestational diabetes, or intrauterine growth restriction.
How is the location of the placenta determined?
The location of the placenta is determined by performing an ultrasound test. Doing an ultrasound is simple and safe. To determine the location of the placenta, the nurse will apply a water-based gel to the abdomen and pelvic area. Then he will place a transducer on his belly. With the help of high-frequency ultrasound waves, the transducer will display the image of your uterus and placenta on a screen. By performing this scan, your doctor will understand whether your placenta is in normal position or not. The ultrasound takes only a few seconds, is painless and absolutely safe, both for the mother and the fetus.
Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.
She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform, Maternicity.com.