When Does The Placenta Take Over? Everything You Need To Know

The placenta is one of the marvellous things about pregnancy. It plays a very important role in pregnancy since it is like a one stop shop for everything that your baby needs while inside the womb. The placenta usually doesn’t get much attention during pregnancy, but do you know that without the placenta the baby cannot survive inside the womb?


It’s likely that you have already heard of the placenta, but do you know what it is, how it is formed, when it takes over and what it does? Before I tell you when the placenta is likely to take over the role of nourishing your baby, it is good to answer these questions; what is the placenta, how is it formed and why is it important.

So What Is This Placenta?

The placenta is an organ that usually attaches itself to the lining of your uterus whenever you get pregnant. It forms a link between your body and that of the baby so as to keep the baby healthy within the womb by carrying out functions that can’t be performed by the baby itself while inside your uterus.

How The Placenta Is Formed

After fertilisation has occurred and the blastocyst has been implanted in the uterus, the ovary from which the ovum came will collapse to form the corpus luteum that will carry out all the functions of the placenta while the placenta is still forming. The development of the placenta starts immediately the baby has been conceived.

It is formed when the collection of cells that has moved to the uterus to be implanted splits and attaches themselves to the deeper parts of the uterine wall. It is these cells that grow to form the placenta, an organ that is entirely made up of blood vessels.

What Is This Placenta

Once it is fully formed, the placenta will take over from the corpus luteum. In any case, a mother conceives twins, the number of placentas formed will vary. For fraternal twins, there will be two placentas, one for each baby.

For identical twins, the number of placentas will depend on when the fertilised egg split to form the embryos. If the placenta formed before the embryo split into two, one placenta would be shared between the two embryos, but if the split occurred before the formation of the placenta, then two placentas will be formed.

When Does The Placenta Become Fully Functional?

Right from the moment a baby has been conceived, the growth and development of the placenta kick off. By the time you are on your 12th or 13th week of pregnancy, the placenta is fully developed and is ready to take over from the corpus luteum. You can actually tell when the placenta is fully developed and has taken over the production of hormones and other functions. One of the signs is the diminishing symptoms of pregnancy like like morning sickness.

Morning Sickness Feels Like

In some women, the placenta becomes fully developed by week 9.

Things That Happen When The Placenta Takes Over

Apart from the disappearance of morning sickness, there are a lot of noticeable things that will be happening to your body during this period. There will be changes in your breasts that will be very noticeable. The sensitivity of your breasts will increase and become a little bit painful. There will also be the darkening of the areola. Your breasts will also start increasing in size as the glands are getting prepared to produce milk for the baby.


As the placenta becomes fully functional by starting to produce hormones, the hormonal levels in your body will surge. The increase in the levels of hormones like progesterone is likely to cause fatigue and emotional changes to you, making it one of the tough times to be your usual self.

The placenta plays a very vital role in sustaining the life of your baby inside the womb by performing the following function:

  • Providing nutrition to the baby

The placenta contains intervillous spaces that allow nutrients and oxygen to pass from the mother’s bloodstream into the fetus bloodstream and also allows for the transfer of carbon dioxide and other waste products from the fetus bloodstream to the maternal bloodstream.

One marvellous thing about the placenta is that it ensures that your blood and that of the fetus do not mix at all since it acts as a blood filter hence it is possible for your baby to have a blood group that is different from yours without any negative reactions from your body.

  • Producing all the necessary hormones to sustain pregnancy and the development of the fetus

Hormones like Human Placental Lactogen (HPL), Progesterone, Estrogen, Oxytocin and Relaxin which are important for both you and your baby during pregnancy are produced by the placenta. Some of these hormones will encourage the formation of blood vessels and organs hence preparing the baby for life outside the womb.

  • Protecting the baby

Your body might contain substances or germs that might cause illnesses to your baby hence the placenta acts as a barrier that blocks the germs and other harmful substances from getting into the fetal bloodstream. Without the placenta’s intervention, your body might reject the baby by treating it as a foreign material.

Things That Affect Placental Health

Being a robust fetal organ, the health of the placenta is very important since it affects the baby’s well-being. Below are the various factors that can impact negatively on the health of the placenta.

  • Age of the mother: As women get older, the likelihood of developing complications in the placenta increases as compared to younger women which can lead to problems during pregnancy.
  • Abdominal trauma: This may be as a result of a fall or any form of a blow to the abdomen.
  • High blood pressure
  • Multiple pregnancy
  • Blood clotting disorders
  • Drug abuse

Therefore, for a healthy placenta, you are required as a mother to be to ensure that you lead a lifestyle that is healthy and void of drug and substance abuse. According to scientists, the genetical composition of the placenta and that of the fetus are the same making fetal health totally dependent on the mother’s lifestyle during pregnancy.

Things That Affect Placental Health

Sometimes things might still go wrong with the placenta even if the mother leads a healthy lifestyle. This may be due to genetic disorders. It is, therefore, advisable for mothers to watch out for any signs that might be as a result of the placenta having some abnormalities. These signs include back pains that are severe, vaginal bleeding and premature uterine contractions.

What Happens To The Placenta After The Baby Is Born?

When the baby is finally born, the placenta ceases to be of use hence it also needs to be taken out of the body since a new one will be formed for the next pregnancy. After the baby is out, more contractions may still follow which helps to push the placenta out. This is the third stage of giving birth.

In case you are too tired to push out the placenta after pushing out the baby, you can be injected with some medicine to initiate contractions in order to push out the placenta. Breastfeeding the baby immediately after birth can also help to stimulate contractions to push out the placenta.


In recap, the placenta is a very important organ for the baby’s life in the womb to be sustained. It is formed from the same cells that form the organs of the baby making its genetic composition and that of the baby similar.

Without it, the fetus cannot make it past eight weeks of pregnancy. Its growth starts immediately the fertilised egg has been implanted onto the walls of the uterus up to the period between the 9th week to the 12th week when it is fully functional.

Kristi Cathey

Hi everyone! My name is Kristi Cathey and I’m glad you found your way to my blog. I am a mother of 3 beautiful angels. This blog was created in order to share my personal experiences in baby care and general health care for pregnant women. If you'd like to get in touch with me, please contact me by sending me an email via kristicathey.intelligentmother@gmail.com. Welcome to Intelligentmother.com

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