Tag: nausea and vomiting of pregnancy

Categories : Obstetrics & GynaecologyTags :

Nausea and Vomiting of Pregnancy Caused by a Complex Inflammatory Response

On By ModernMedia
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UCLA researchers have uncovered a link between “morning sickness” symptoms and the body’s natural, but complex, inflammatory response to biological and bodily changes during pregnancy.

According to the National Institutes of Health, up to 80% of early-stage pregnant mothers experience some nausea, vomiting and aversions to certain foods and smells. While uncomfortable, these symptoms are not typically a sign that anything is wrong with the health of the mother or the developing fetus, but rather an indication of a delicate balance unique to pregnant women. 

“During pregnancy, a mother’s immune system faces a tricky challenge: it has to protect both her and the foetus from infection, but without accidentally attacking the foetus, whose genetic identity is half-foreign because it is half derived from the father. Normally, the immune system attacks anything that seems foreign, so in pregnancy, it has to carefully adjust to keep the foetus safe while still defending against infection,” said UCLA anthropology professor Molly Fox, corresponding author of the study published in Evolution, Medicine and Public Health.

The researchers believe that this delicate balance, which protects mother and foetus, is achieved by a unique mix of inflammatory responses. They function to prevent the mother’s body from rejecting the foetus, alongside adaptive behavioural mechanisms, like nausea, that encourage the mother to avoid foods that are potentially harmful, especially in the first and second trimesters when the foetus is most vulnerable.

“Nausea, vomiting or aversions to foods or smells are not indications that something is going wrong for the mother or the foetus. It’s likely an indication that everything is moving along normally, and a reflection of the body’s healthy and helpful immune response,” said UCLA anthropology professor and paper co-author Daniel Fessler.

Methodology and findings

For the study, the UCLA-led team of anthropologists and epidemiologists collected and analysed blood samples to measure immune system molecules called cytokines. Cytokines are proteins that send signals to help the body launch a quick defence against sickness and regulate inflammation. Participants also filled out questionnaires that asked about morning sickness-related symptoms and food and smell aversions during the early stages of pregnancy. The participants were 58 Latina women in Southern California who were followed beginning in early pregnancy through the postpartum.

Sixty-four percent of study participants experienced odour or food aversions, primarily to tobacco smoke and meat. Sixty-seven percent reported nausea and 66% experienced vomiting.

The study team measured pro-inflammatory cytokines as well as anti-inflammatory cytokines. They found that women who experienced an aversion to tobacco smoke showed a noticeable shift toward a more inflammatory response. Food aversions, nausea and vomiting were also associated with a more pro-inflammatory immune balance.

An evolutionary process?

The correlation is consistent with researchers’ theory that these symptoms may be part of an evolutionary adaptation that helps pregnant mothers’ bodies minimize exposure to harmful substances, though the study’s authors caution that the evidence is not definitive and more research is needed. 

They emphasised that the study allowed the team to look at both human biological and behavioural responses during pregnancy.

“In many mammals, the foetal compartment has barriers separating it from the mother’s blood supply, where her immune cells are. But in humans, we have a unique setup – foetal cells are bathed in maternal blood. Humans have the most invasive of all placentas, burrowing deep into maternal tissue. So humans need unique strategies to prevent the mother’s immune system from attacking the foetus,” said Fox.

These immunological changes may induce nausea, which in turn encourages food avoidance that might act as an additional layer of protection, according to the researchers

“Nowadays, you will see labels on packages of ground beef or soft cheese that warn pregnant women to be cautious about these products because of the risks of foodborne illness during pregnancy. Aversions to certain odours and foods, and nausea and even vomiting, appear to be evolution’s way of achieving that same objective,” said Fessler.

Practical implications

The researchers, including first author Dayoon Kwon, who just completed her PhD in epidemiology at UCLA (and is now a postdoctoral fellow at Stanford), said that the study could help bolster recognition that nausea and vomiting are normal symptoms with biological underpinnings associated with healthy pregnancies. The study’s results could help in paving the way for common-sense workplace accommodations, such as more efficient deployment of health care benefits and other helpful resources to reduce stigma, excessive absences and lost productivity.

They also encourage other researchers to continue to look into the questions raised by the study, to not only explore the evolutionary questions, but to work toward providing clinicians with non- or low-invasive measures of prognoses.

Source: University of California – Los Angeles

Categories : Obstetrics & GynaecologyTags :

Cause of Pregnancy Sickness – and Potential Treatment

On By ModernMedia
Photo by Anna Hecker on Unsplash

A Cambridge-led study has shown why many women experience nausea and vomiting during pregnancy – and why some women, including the Duchess of Cambridge, become so sick they need to be admitted to hospital.

The culprit is a hormone produced by the foetus – a protein known as GDF15. But how sick the mother feels depends on a combination of how much of the hormone is produced by the foetus

The discovery, published today in Nature, points to a potential way to prevent pregnancy sickness by exposing mothers to GDF15 ahead of pregnancy to build up their resilience.

As many as seven in ten pregnancies are affected by nausea and vomiting. In some women – thought to be between one and three in 100 pregnancies – it can be severe, even threatening the life of the foetus and the mother and requiring intravenous fluid replacement to prevent dangerous levels of dehydration. So-called hyperemesis gravidarum is the commonest cause of admission to hospital of women in the first three months of pregnancy.

Although some therapies exist to treat pregnancy sickness and are at least partially effective, widespread ignorance of the disorder compounded by fear of using medication in pregnancy mean that many women with this condition are inadequately treated.

Until recently, the cause of pregnancy sickness was entirely unknown. Recently, some evidence, from biochemical and genetic studies has suggested that it might relate to the production by the placenta of the hormone GDF15, which acts on the mother’s brain to cause her to feel nauseous and vomit.

Now, an international study, involving scientists at the University of Cambridge and researchers in Scotland, the USA and Sri Lanka, has made a major advance in understanding the role of GDF15 in pregnancy sickness, including hyperemesis gravidarum.

The team studied data from women recruited to a number of studies, including at the Rosie Maternity Hospital, part of Cambridge University Hospitals NHS Foundation Trust and Peterborough City Hospital, North West Anglia NHS Foundation Trust. They used a combination of approaches including human genetics, new ways of measuring hormones in pregnant women’s blood, and studies in cells and mice.

The researchers showed that the degree of nausea and vomiting that a woman experiences in pregnancy is directly related to both the amount of GDF15 made by the foetal part of placenta and sent into her bloodstream, and how sensitive she is to the nauseating effect of this hormone.

GDF15 is made at low levels in all tissues outside of pregnancy. How sensitive the mother is to the hormone during pregnancy is influenced by how much of it she was exposed to prior to pregnancy – women with normally low levels of GDF15 in blood have a higher risk of developing severe nausea and vomiting in pregnancy..

The team found that a rare genetic variant that puts women at a much greater risk of hyperemesis gravidarum was associated with lower levels of the hormone in the blood and tissues outside of pregnancy. Similarly, women with the inherited blood disorder beta thalassemia, which causes them to have naturally very high levels of GDF15 prior to pregnancy, experience little or no nausea or vomiting.

Professor Sir Stephen O’Rahilly, Co-Director of the Wellcome-Medical Research Council Institute of Metabolic Science at the University of Cambridge, who led the collaboration, said: “Most women who become pregnant will experience nausea and sickness at some point, and while this is not pleasant, for some women it can be much worse – they’ll become so sick they require treatment and even hospitalisation.

“We now know why: the baby growing in the womb is producing a hormone at levels the mother is not used to. The more sensitive she is to this hormone, the sicker she will become. Knowing this gives us a clue as to how we might prevent this from happening. It also makes us more confident that preventing GDF15 from accessing its highly specific receptor in the mother’s brain will ultimately form the basis for an effective and safe way of treating this disorder.”

Mice exposed to acute, high levels of GDF15 showed signs of loss of appetite, suggesting that they were experiencing nausea, but mice treated with a long-acting form of GDF15 did not show similar behaviour when exposed to acute levels of the hormone. The researchers believe that building up woman’s tolerance to the hormone prior to pregnancy could hold the key to preventing sickness.

Co-author Dr Marlena Fejzo from the Department of Population and Public Health Sciences at the University of Southern California whose team had previously identified the genetic association between GDF15 and hyperemesis gravidarum, has first-hand experience with the condition. “When I was pregnant, I became so ill that I could barely move without being sick. When I tried to find out why, I realised how little was known about my condition, despite pregnancy nausea being very common.

“Hopefully, now that we understand the cause of hyperemesis gravidarum, we’re a step closer to developing effective treatments to stop other mothers going through what I and many other women have experienced.”

The work involved collaboration between scientists at the University of Cambridge, University of Southern California, University of Edinburgh, University of Glasgow and Kelaniya University, Colombo, Sri Lanka. The principal UK funders of the study were the Medical Research Council and Wellcome, with support from the National Institute for Health and Care Research Cambridge Biomedical Research Centre.

The original text of this story is licensed under a Creative Commons License. 

Source: University of Cambridge