Hyperemesis Gravidarum – How Sick is too Sick?

Nausea and vomiting are both common early pregnancy signs for many people. It’s thought that up to 94% of women can experience nausea and vomiting in pregnancy to some degree.

The pesky double act is generally accepted as one of those unavoidable annoyances of early pregnancy – annoying, but generally expected, and overall, a welcome experience and sign that things are progressing well in the early stages.

Typically, nausea and vomiting symptoms come at a time where some may be trying to hide their newly discovered secret from family, friends, or colleagues until they are a little further along – maybe until they’ve adjusted to the idea of becoming a parent – perhaps for the first time, or until they have their first pregnancy ultrasound safely under their belt. But for a small percentage of women, it will be near impossible to hide the severity of their symptoms.

A lesser-known condition, called Hyperemesis Gravidarum [‘hyper’, meaning excessive, ‘emesis’, meaning vomiting, ‘gravidarum’, meaning pregnancy], also known as HG, will be experienced in around 1-3% of those with pregnancy related nausea and vomiting.

Morning Sickness vs Hyperemesis – What’s the Difference?

Nausea and vomiting in pregnancy (NVP) are considered along a spectrum – meaning that those who experience it will experience it in varying degrees ranging from mild to severe.

So, let’s have a look at some of the differences:

Mild NVP

Mild NVP is often referred to as morning sickness, although this is now deemed an outdated term. For any of you who have experienced it, you’ll probably be aware that ‘morning sickness’ doesn’t always occur in the morning as its cheery name suggests. Sickness can occur at any time of the day (or night). This type of nausea and vomiting involves short or occasional bouts of sickness experienced mainly in the first trimester (the first 12 weeks). Often beginning around 6 weeks and peaking around 9 weeks of pregnancy. For most, the symptoms will ease in the second trimester (12-28 weeks) and can usually be managed successfully through diet and lifestyle changes, without too much disruption to day-to-day activities.

Moderate – Severe NVP

Moderate to severe NVP can often be mistaken as mild NVP, creating a barrier and challenge to accessing treatment for those who may benefit from it. Moderate to severe NVP is more persistent and results in more frequent episodes of nausea and vomiting. Again, symptoms can occur at any point throughout the day, but often persist beyond the first trimester, with some experiencing symptoms up to 20 weeks or beyond. Some people can also experience excessive saliva production, adding to their feelings of nausea or vomiting. Although diet and lifestyle changes may make symptoms more manageable, for some, treatment may be necessary. Those suffering with moderate or severe NVP, may require emotional and psychological support as quality of life may be impacted, it may be difficult to manage normal routines or activities, and some will experience weight loss.

Hyperemesis Gravidarum

Hyperemesis is not simply ‘bad morning sickness’. Hyperemesis is a debilitating condition, thought to affect approximately 30,000 people per year in the UK. It is defined as nausea and vomiting which begins in early pregnancy, not caused by any other condition, which causes a severe inability to eat and drink normally and has a severe effect on daily activities. Severe vomiting as experienced in HG can lead to dehydration, weight loss, malnutrition, and organ damage for the mother, as well as having significant adverse fetal effects too.

HG can begin very early in pregnancy – sometimes even before a positive pregnancy test! Symptoms tend to peak around 9-13 weeks and can improve around 16-24 weeks. But for around 1 in 5 people with HG, symptoms will persist throughout the entire pregnancy. Due to the individual being unable to keep down food or even fluids sometimes, they can become unwell very quickly. Weight loss and dehydration can be quick and severe and medical treatment and/or hospital admission is needed to reduce further complications.

The impact on an individual’s quality of life, normal activities and emotional and mental wellbeing will be significant and psychological support will be beneficial for those experiencing HG in their pregnancies.

Some people can experience ‘dry’ HG or NVP, which doesn’t involve actual vomiting, only nausea. However, symptoms can still be so severe that it impacts on an individual’s ability to eat and drink, resulting in dehydration and malnutrition in the same way.

New Advances in HG Research

Despite nausea and vomiting being the second most common reason for hospital admission in pregnancy (preterm labour being the first), until recently, conclusive information on the cause of HG has been missing.

It’s long been thought that the cause of HG was down to high levels of various pregnancy related hormones. Studies have previously focused on changes in hCG (human chorionic gonadotrophin), and steroid hormones such as cortisol, estrogen and progesterone due to their presence and rising levels in early pregnancy. However, new research has suggested there may be another player in the mix responsible for causing HG.

GDF15 (Growth and Differentiation Factor 15) is a protein made in low levels in all tissues outside of pregnancy, but one which is also produced by the fetus in pregnancy. GDF15 acts on the mother’s brain causing nausea, vomiting and taste aversion. Leading researchers believe that high levels of GDF15 in the maternal bloodstream are associated with pregnancy related sickness and HG. However, it’s been discovered in recent research, that women with high levels of GDF15 before pregnancy (such as those with Beta-Thalassemia which causes chronically high levels of GDF15), had minimal reactions to it during pregnancy, leading to low levels of sickness.

A combination of the level of GDF15 produced by the fetus, and maternal sensitivity to the hormone is thought to determine the severity of sickness experienced.

Some people with HG are known to have variation in the gene that codes for GDF15 which causes them to produce abnormal levels of the hormone and/or have an abnormal sensitivity to it in pregnancy.

Interestingly, it is thought that exposure to GDF15 outside of pregnancy, may be the key to reducing the severity of the condition. This breakthrough discovery is monumental in leading the way towards prevention of NVP and HG. Exposure to GDF15 prior to pregnancy may help to build maternal resilience and tolerance, reducing their sensitivity to the protein during pregnancy.

It’s hoped that one day a test can be created to identify those most at risk of developing severe NVP and HG.

“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”

~ Professor Stephen O’Rahilly, University of Cambridge