The placenta is a temporary organ that forms in the mother’s uterus during pregnancy. It links mother and fetus by the umbilical cord bringing oxygen and all of baby’s nutrients throughout the pregnancy as well as taking away all the waste materials. The placenta is expelled from the body after the baby is born, referred to as the 3rd stage of labour. Every human starts out life attached to a placenta, therefore scientists believe the placenta is a fetal organ, even though it is often portrayed as the woman’s issue because it develops in the mother’s body.
The word placenta comes from the Latin word for cake.
A placenta is a roughly the size of a dinner plate and is a saucer shape, being thicker in the middle and thinning out towards the edges. It weighs around 1lb. It has a maternal side and a fetal side. The maternal side is attached to the uterine wall and the fetal side is attached to the fetus by the umbilical cord. Along the fetal side of the placenta you can clearly see veins in a tree like pattern.
It also has an umbilical cord. This is the link between the fetus and the mother and is formed by around the 5th week of gestation. It normally contains 2 arteries and 1 vein, surrounded by Wharton’s jelly. The cord grows with the fetus during pregnancy, usually measuring the same as the crown to rump length.
The role of the placenta is just immense. One of the first things it does is to release the hormone ‘human chorionic gonadotropin’ (the hormone that tells your pregnancy test your pregnant). hCG is responsible for stopping your body from shedding the uterine wall (a period). If this hormone wasn’t produced it would result in the fetus being spontaneously aborted. As well as this hCG assists a male fetus by stimulating the testes to produce testosterone, which is needed to help the male sex organs to grow. hCG is also thought to have an anti-antibody effect, protecting the placenta and the fetus from being rejected by the mother’s normal immune response as they could be seen to be foreign bodies. Other hormones are also produced such as Human placental lactogen, progesterone and estrogen. All of these support fetal growth and nutrition. Estrogen is crucial in production of milk and is responsible for increased blood supply towards the end of the pregnancy.
It functions as the lungs, kidneys and liver as well as the immune, endocrine and the gastrointestinal systems for the fetus.
All of the fetus’ waste including carbon dioxide is passed from the fetus through to the mother’s blood via diffusion across the placenta. Nutrients and oxygen from the mother are passed through the placenta to the fetus.
As early as the 20th week of gestation some antibodies can be passed through the placenta providing protection to the fetus. This passive immunity can stay with the baby for several months after birth. This provides the infant with an exact copy of the mother’s immunity staying with the newborn during the first few months of his/her life.
The placenta also provides a reservoir of blood and can act as a kind of capacitor by delivering bloody in case of hypotension.
A healthy placenta sustains fetal life whist in the mothers uterus however if the placenta doesn’t work as it should it could lead to both the mothers and fetus’ demise.
Placental abruption is where the placenta prematurely detaches away from the wall of the uterus. Depending on the degree of abruption and gestation of the fetus will depend on whether the pregnancy continues with bed rest or whether the baby needs to be delivered. Without any form of medical intervention placental abruption has a high maternal mortality rate.
Placenta accreta is where the placenta attaches abnormally to the muscle layer of the uterus called the myometrium. Placenta accreta is defined by three grades depending on the depth of attachment into the muscle layers.
The highest risk of the condition is Placenta percreta. This accounts for 5-7% of the condition and can attach to other organs including the bladder.
Placenta increta accounts for 17% of the condition and is less severe.
Placenta accreta is the most common form accounting for around 75% of the condition. Accreta is less invasive and doesn’t actually penetrate the muscle wall.
Placenta accreta has a higher chance of maternal fatality if it isn’t diagnosed before birth and treated correctly.
Placenta praevia is a condition where the placenta attaches near or over the cervix. Complications can lead to placenta accreta and restriction with fetal growth. Babies are generally delivered via caesarean section.
The placenta separates away from the uterine wall and is delivered after the baby has been be born. Generally, this can be physiological managed or by active management.
An actively managed third stage involves having an injection of ergometrine or syntocine (synthetic oxytocin) administered to the mother’s upper thigh just after the baby is born. It can speed up the delivery of the placenta. By having a managed third stage it is thought to reduce the risk of a severe haemorrhage in some high risk women.
In a small number of cases some or all of the placenta can be retained inside the uterus. In the case of a retained placenta of partially retained placenta after physiological management has been tried, it may be necessary to manually remove what has been retained.
Once the placenta has been delivered, the umbilical cord clamped and separated from the baby it has served its purpose.
However, some people believe the placenta has many benefits after birth. It is thought that by consuming a healthy placenta by either eating, drinking or by encapsulation it can prevent postnatal depression, improve energy, improve milk supply reduce postnatal bleeding and provide iron.
In the case of a lotus birth the placenta isn’t clamped or detached from the baby by cutting. The baby and placenta stay attached until the umbilical cord separates naturally. This can take anything from around 3 to 10 days.