The Amazing Life-Giving Placenta: All Your Questions Answered
The way our bodies support and protect us often seems like magic. The placenta is a unique example of the female body’s ability to adapt and transform to support new life. In this article, you’ll learn all about this incredible temporary organ and its functions.
Existing only during pregnancy, the placenta is our first source of nourishment, oxygen, and immune protection. This life-giving organ is vitally important, yet often ignored when we talk about pregnancy and childbirth. This article will shed some light on the magic of the placenta.
What is the placenta?
The placenta is a temporary organ that begins to form inside the uterus just after conception. It serves as an interface between the mother’s body and her growing foetus, allowing her to share the life-supporting functions the organs of her body provide.
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As long as the baby remains within its mother’s womb, she provides it with oxygen, nutrients, and other essential functions, mediated by the placenta, to ensure its safe and healthy development.
How does the placenta form?
Once a sperm fertilizes the egg, the merged cells begin to multiply through cell division. By day five or six, a clump of 200–300 cells (the blastocyst) will have formed. These cells are already differentiating into an inner cell mass (the embryoblast), which becomes the embryo, and an outer layer of cells (the trophoblast) that gives rise to the chorion and the amnion—two membranes that surround and protect the foetus throughout pregnancy.
The blastocyst rolls along the uterine wall until it begins to adhere thanks to chemical signalling between the trophoblast and the endometrium, or uterine lining. As the blastocyst embeds itself into the uterine wall, small projections from the chorion, called chorionic villi, extend into the uterus. As they grow, they develop the special vascular system of the placenta that enables the exchange of nutrients, waste, and oxygen between the maternal blood supply and the foetal blood supply without allowing them to mix.
The placenta continues to develop throughout the first trimester. By week 14 the infrastructure is complete, but the placenta continues to grow and adapt to the needs of the developing baby until around 34 weeks.
A mature placenta is a dark reddish-blue, spongy disk-like organ with several lobes, averaging 22 cm (9 inches) in diameter and 2–2 ½ cm (0.8–1 inch) thick, and weighing around 500 grams (1 lb). A strong, stretchy umbilical cord containing one vein and two arteries connects the placenta to the baby’s abdomen in the spot that later becomes the belly button.
What does the placenta do?
The placenta is a multi-tasking organ, providing five essential functions that support the growing baby.
- Lung function: Inside the mother’s womb, the developing foetus is encased in a fluid-filled amniotic sac that provides a safe environment for the skeleton and organs to develop. As the baby’s lungs aren’t fully formed until week 36, its blood is oxygenated within the placenta with oxygen supplied by the mother’s blood. Bright red, oxygenated blood is delivered to the foetus by means of the umbilical vein, and the umbilical arteries return the darker red, deoxygenated blood back to the placenta where it can be resupplied.
- Kidney function: The placenta also cleans and balances the baby’s blood by filtering out bicarbonate, hydrogen ions, lactic acid, and other chemicals, much like the kidneys do in adults and children once they are outside the womb.
- Nutritional function: The placenta supplies the baby with all the essential nutrients, vitamins, and micronutrients it needs to develop. These are also extracted from the maternal blood supply. This is why it is essential for pregnant women to eat well and follow their doctor’s advice regarding prenatal dietary supplements. For example, many women experience prenatal anaemia, because once the baby has had its needs satisfied there is not enough iron left over for the mom.
- Immune function: Inside the womb, the developing foetus is protected by its mother’s immune defences. If an infection is detected, antibodies from the mother travel through the placenta to protect the baby. And if a mom gets sick or has a vaccine jab during pregnancy, her baby will be born with antibodies for those particular infections. This immune protection lasts two to three months after the baby is born to give it a head start on developing its own immune response, and antibodies and other immune factors continue to be transferred from the mother through her breast milk as long as the baby nurses. (This is called passive immunity.)
- Endocrine function: As the baby can’t yet synthesize its own hormones, the placenta works as an endocrine organ. The main hormone it produces is human chorionic gonadotropin (hCG). This hormone signals to the body not to shed the uterine lining this month, but to thicken it instead to support the growing embryo. The placenta also produces oestrogen, which softens and protects the uterus during pregnancy, and helps develop the baby’s organs, and stimulates the mammary glands to prepare for breastfeeding. The third hormone is progesterone, which maintains the pregnancy and prevents premature contractions. The placenta also produces human placental lactogen (hPL), which nourishes the growing foetus and stimulates milk glands to prepare for milk production. The placenta also produces hormones such as kisspeptin, soluble endoglin (sEng), soluble fms-like tyrosine kinase 1 (sFlt-1), and placental growth factor (PlGF) to support its own development and integrity of the.
Delivery of the placenta
The placenta is needed only during pregnancy. Once the baby is born, it no longer serves a purpose. As the now empty uterus contracts back to its original size, the placenta is squeezed out of the uterine wall and maternal blood vessels that nourished the placenta are closed off.
The delivery of the placenta is considered the 4th stage of labour. This needs only a contraction or two and usually takes place within 30 to 60 minutes after the baby is born. After the effort needed for cervical dilation and childbirth, 4th stage contractions are hardly noticeable and the mother’s attention will be focused on her newborn.
Delivery of the entire placenta is very important. Retained placenta is a potentially dangerous condition, as any material left in the uterus will keep it from properly contracting and closing off the mother’s blood vessels after birth.
In the past, a mother could bleed to death after delivering a healthy baby because her uterus failed to fully contract and close off the blood vessels feeding the placenta. These days, doctors and midwives are trained to recognize the potential for postpartum haemorrhage. While potentially life-threatening, a retained placenta is easily dealt with.
If all goes well, the placenta is delivered quickly and cleanly, so the uterus can shrink with a few final contractions and compress the blood vessels. This all happens during the golden hour after delivery, when ideally the newborn is lying skin-to-skin on its mother’s chest, taking in the new environment. Often alert from the work and rush of hormones, the new baby will eventually find its mother’s nipple and start to suck. This nipple stimulation releases more oxytocin, which encourages the uterus to fully contract. It’s a very clever system.
If the baby is delivered by C-section, the doctor will surgically remove the placenta and ensure the uterus contracts properly. Mother and child will probably be a bit less exhausted for their first bonding experience.
The four most common placental disorders
Over the course of your pregnancy, your ob/gyn will monitor the placenta as well as your baby, looking for any possible complications or placental disorders.
Placental placement
Usually, the blastocyst will embed itself in the uterine wall in a place where there is plenty of room for the placenta to grow to its full size without affecting foetal development or birth. But sometimes, things don’t go as smoothly as we’d like.
Placenta previa
When the blastocyst implants in the lower part of the uterus, the placenta may grow to cover some or all of the cervix. This is called placenta previa because the placenta “goes before” the baby, potentially blocking delivery or posing a high risk of bleeding as the placental tissues are at risk of being torn or disturbed by the movement of the baby through the birth canal.
If an early ultrasound shows a low-placed placenta, it may not be cause for concern. As the uterus grows, the placenta will move away from the cervix and the problem can resolve itself. However, bright red vaginal bleeding and/or contractions in the second trimester may indicate a problem.
To avoid complications and bleeding, your doctor may recommend taking things slow and avoiding strenuous activities such as cardio exercises, having sex, and other high-impact movements as your pregnancy progresses. If the placenta is too close to the cervix when labour starts, the safest course of action is to deliver the baby by C-section.
Placental attachment
The placenta is designed to detach from the uterus once the baby is born. But sometimes the placenta is so firmly attached it is difficult to dislodge.
Placenta accreta
One of the most common placental complications is when the placental tissues grow deeply into the endometrium, or uterine lining.
Women over the age of 35, those who have had previous pregnancies, and those who have delivered by C-section or have had any type of uterine surgery have a higher risk of developing placental attachment complications, possibly due to the presence of scar tissue or simply wear and tear on the uterus.
Placenta increta is when the placenta grows through the endometrium and attaches to the uterine muscle tissues.
Placenta percreta is when the parts of the placenta grow through the wall of uterus, sometimes even reaching other organs, such as the bladder, colon, or blood vessels.
These conditions have no discernible symptoms, so they are usually detected during an ultrasound scan. While they rarely affect foetal development, any one of these can pose a serious risk to the mother if not detected and dealt with. Because vaginal delivery would place the mother at a high risk of excessive blood loss, any of these conditions will generally necessitate a C-section, potentially followed by a hysterectomy to avoid future danger.
What happens to the placenta afterwards?
Once the placenta has been successfully delivered, the midwife or doctor will examine it for abnormalities and make sure it is complete. If there is reason to suspect a problem, material from the placenta can be tested for infection or inflammation so a proper course of medicine can be prescribed for the newborn.
If there were any complications during pregnancy or labour, the hospital can perform additional analyses to better understand what conditions may have affected the course of the pregnancy and the health of the mother and baby.
If, upon examination, the placenta does not look complete, steps will be taken to remove the retained placenta.
After the placenta has given up all its secrets, the parents can generally choose whether to keep it or leave it with the hospital for disposal as biomedical waste. Hospitals must follow strict protocols to prevent the potential spread of infectious diseases.
Can I keep the placenta?
Many families have cultural, religious, or personal reasons for keeping the placenta. However, once it is no longer attached to a living body, the placenta will quickly begin to deteriorate and can easily become a breeding ground for bacteria. If you do want to keep it, you will need to prepare the placenta for safe handling, transportation, and storage.
Why you may want to keep your placenta
Spiritual or symbolic traditions
There are many traditions, beliefs, and myths surrounding the power and importance of the placenta. In some cultures, the placenta is considered a sacred organ. Your family may follow certain traditions or rituals associated with the placenta, such as burying it in a special location or planting a tree over it to honour the birth of your child.
Nutrition or medicine
In the animal world, it is common practice for the mother to consume the placenta, or afterbirth. Biologists consider this instinctual behaviour, possibly meant to hide any trace of birth from potential predators. Humans may also have done this in the distant past, but there is little direct evidence. However, in some cultures, the placenta is known to have been used in traditional medicine for a variety of cures.
In modern times there has been a resurgence of interest in the mother consuming her placenta to balance hormones, boost energy levels, or reduce the risk of postpartum depression. However, scientific evidence supporting these claims is limited.
Those who choose to do this, generally hire a placental encapsulation specialist who collects the placenta from the hospital in a cooler, then steams it, dehydrates it, and grinds it into a powder. The placenta powder is stored in gelatine capsules that the mother can use at her leisure without fear of disease or contamination.
Creative projects
Not only does the placenta function as “the first mother”, but the network of blood vessels on the side facing inwards looks like “the tree of life”. People draw a wide range of personal meanings from this unique structure and use it in some way to create lasting art. For example, you can cast the placenta in resin, create prints with placental blood, or preserve an imprint of the unique blood vessel network that supported your child’s foetal development. There are businesses that offer to preserve a bit of the placenta in jewellery and other adornments so that you can keep it forever.
Medical research
More scientifically minded families may choose to donate the placenta for medical research, education, or therapeutic purposes. Placentas contain valuable stem cells and tissues that can be used to advance research into regenerative medicine, tissue engineering, and the development of new medical treatments.
Final words
Researchers estimate that at least one hundred billion humans have lived and died since the dawn of humanity. This means more than 100 000 000 000 placentas have supported as many developing babies. And yet so much of this amazing process remains a mystery. We hope this article has given you a little insight into the wonders of the placenta.
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