The placenta is remarkable – a temporary organ that nourishes and protects the fetus – and is then discarded when its job is complete. It acts as a gatekeeper between mother and fetus by allowing oxygen and nutrients in while filtering out potentially harmful substances that can affect fetal health. In a world where increasing numbers of environmental pollutants may be putting pregnancies at risk, can the placenta still do its best job?
What is the placenta, and what does it do?
The placenta has two main functions. Firstly, it allows oxygen and nutrients to pass from the mother to the fetus via the umbilical cord. Secondly, it enables waste products from the fetus, such as urea and carbon dioxide, to be removed. It has additional functions which we’ll look at later.
The placenta develops as an organ shortly after embryonic cells have been implanted. It attaches to the wall of the uterus, at the top, side, back or front. If it develops low in the uterus it will likely move up during pregnancy, but it could pose a risk of placenta previa.
In this condition, the placenta lies low over the cervix, which can lead to heavy bleeding.
The placenta is vital to the fetus, which is why healthcare providers regularly monitor the health and position of the placenta.
In addition to its two main roles, the placenta also carries out the following tasks:
Transfers antibodies from mother to fetus. Antibodies offer protection against viruses and bacteria. During pregnancy, particularly the last trimester, antibodies pass from the mother to the fetus via the placenta. This gives the fetus temporary immunity to potential infection after birth. This diminishes over time and is then boosted by childhood vaccinations.
Produces hormones. The first hormone produced by the placenta is human chorionic gonadotropin (hCG) which stops the menstrual cycle, helping to secure the pregnancy. It is the hormonal marker for pregnancy and is registered by testing kits. The placenta also produces progesterone, which supports the implantation of the embryo. In addition, it provides estrogen, which plays a vital role in milk production and the mother’s physical changes in breast and uterus size thereby supporting the foetuses development.
Acts as a barrier. Furthermore, the placenta acts as a barrier to prevent blood and possible infection from passing from the mother to the fetus. However, it cannot block every potential contaminant, and any medicines, alcohol or nicotine (from cigarettes or vaping) consumed by the mother can affect the placenta and be passed to the fetus. That’s why it is so important to abstain from smoking and drinking alcohol when pregnant and to always seek advice about any risks that even over-the-counter medicines or health supplements may pose for the fetus.
Has the potential to save lives. After delivery, the umbilical cord is cut, thereby ending the protection the placenta has provided the fetus for forty weeks. The placenta is then usually delivered naturally, in what is considered the third stage of labour, and disposed of. However, there are calls for more women to donate their umbilical cord and placenta as they store blood stem cells that can be used to treat several diseases and disorders. Stem cells from cord blood have cured leukaemia (blood cancer), sickle cell anaemia and thalassaemia, and reversed bone marrow failure. These stem cells also have a positive effect on immunodeficiencies and metabolic disorders. So, this vital organ which has nurtured and maintained the life of a fetus for nine months has the potential to support and heal many more people when donated.
Pregnant women can actively improve their chances of a successful pregnancy with a healthy varied diet, and limiting or completely abstaining from smoking, alcohol and drugs. They should also be vigilant concerning their intake of health supplements and medication. Any or all of these could pose a threat to the fetus. But what about the less obvious threats?
Unfortunately, there are risks to pregnancy that come from the environment over which women have little control. Air pollution, which can be laden with carbon monoxide and nitrous gases, can affect human health. Chemicals found in everyday household products such as cleaners, aerosols, paint, hair dye and weedkillers can be absorbed via the skin or inhaled, causing potential harm to the mother and fetus.
A newer concern is the proliferation of microplastics which find their way into water and food. Worryingly, an examination of the placenta and meconium has confirmed the presence of microplastics. These have transferred from the mother to the placenta and even onwards through the umbilical cord to the fetus.
While the placenta does an astounding job at nurturing and protecting the growing fetus, a study has shown that environmental hazards such as microplastics and black carbon from air pollution breach its defences. Another study discovered carbon-based particles in the placentas of 11 healthy women but also nanoparticles of iron, phosphorus, silica, calcium, zinc and titanium.
It’s not known whether these particles had been transferred to the fetus, but it is recognised that a compromised placenta that is not functioning properly can contribute to pre-term birth and even poor childhood health.
We know the placenta usually provides excellent protection and creates the ideal environment for the growing fetus, but it is concerning to see that new threats from plastic and the air around us can reach the placenta and possibly affect fetal health.
The placenta has provided every one of us with vital resources since the earliest days of conception. In most pregnancies, it enables the fetus to grow steadily and transfers protective antibodies for life after birth. It even can heal other people via stem cell donation.
It is, however, very difficult to undertake research on a living, working placenta in situ, even though surgeons can perform lifesaving operations to repair placentas that are not functioning properly.
That makes the work of the LifeSaver Project so unique and important. The project plans to develop a realistic organic model of the placenta outside the body to test medicines and examine the threats of present and future environmental pollutants. And it will do so without causing harm to the fetus, the mother, or the animals so often used in medical testing.