Hyperemesis gravidarum

Hyperemesis gravidarum, often shortened to HG, is a severe form of nausea and vomiting in pregnancy. It is more than ordinary morning sickness. RCOG describes HG as pregnancy sickness that becomes so severe that it stops you carrying out normal daily activities and makes it difficult to eat and drink normally.

HG can leave you feeling physically exhausted and can affect work, home life, relationships and emotional wellbeing. If you are struggling to keep food or fluids down, becoming dehydrated or finding that sickness is taking over your daily life, contact your midwife, GP or maternity service. Assessment and treatment are available.

What is hyperemesis gravidarum?

Nausea and vomiting are common during pregnancy, but HG sits at the severe end of pregnancy sickness.

According to RCOG, hyperemesis gravidarum may affect up to 3 in 100 pregnant women. It can cause dehydration and may require hospital treatment.

The NHS lists prolonged and severe nausea and vomiting, dehydration and weight loss among the signs and symptoms of HG.

Dehydration can cause symptoms such as:

feeling very thirsty
feeling tired, dizzy or lightheaded
passing less urine than usual
dark yellow, strong-smelling urine

Some people with HG are unable to keep down enough food, fluids or medication. If that is happening, seek medical advice rather than trying to manage severe symptoms alone.

How is HG different from morning sickness?

Morning sickness can still be unpleasant and disruptive, but HG is considerably more severe.

With HG, nausea and vomiting may prevent you from eating and drinking normally or carrying out ordinary activities. The NHS notes that people with HG may be sick many times a day and unable to keep food or drink down.

Symptoms can also last longer than typical pregnancy sickness. The NHS says ordinary nausea and vomiting often improves or stops around weeks 12 to 20, while HG may continue beyond this and, for some people, may not fully resolve until after the baby is born.

The severity of your symptoms matters more than the label you use. If pregnancy sickness is preventing you from functioning normally or keeping fluids down, speak to a healthcare professional.

What causes hyperemesis gravidarum?

The exact cause of HG is not fully understood.

The NHS says there is evidence that it is linked to hormonal changes during pregnancy. RCOG also notes research suggesting that genetic differences and higher levels of a hormone called GDF-15 may help explain why pregnancy sickness is more severe for some people.

Having experienced HG before can increase the likelihood of experiencing it in another pregnancy. The NHS also notes evidence that HG can run in families.

HG is a medical condition. Severe sickness is not a sign that you have failed to eat correctly, manage pregnancy well enough or cope with symptoms in the right way.

How is hyperemesis gravidarum assessed?

If your symptoms do not settle, RCOG advises contacting your GP or midwife. You may be referred to an assessment unit in a maternity or gynaecology service.

Healthcare professionals may ask about how long you have been unwell, how much you are able to eat and drink, whether you have lost weight, medicines you have tried and whether you have other symptoms.

RCOG says an assessment may also include checks such as your temperature, pulse, breathing rate, blood pressure and weight, along with an assessment for dehydration or undernutrition. Urine and blood tests may be carried out, and an ultrasound scan may be offered if you have not already had one.

Other possible causes of vomiting may need to be considered, particularly if you have abdominal pain, pain when passing urine, another medical condition or vomiting that begins after 16 weeks.

How is hyperemesis gravidarum treated?

Treatment depends on how severe your symptoms are and whether you can keep fluids and medication down.

RCOG states that several anti-sickness medicines are available for nausea and vomiting during pregnancy. A healthcare professional can discuss the options, potential benefits and possible side effects with you.

If you cannot drink enough, you may be offered fluids through a drip. Some people can receive this treatment during a hospital assessment and return home afterwards if they improve.

Hospital admission may be advised if you are dehydrated, have severe vomiting and cannot keep fluids or oral medication down, have abnormal blood test results, have lost a lot of weight rapidly, or have certain medical conditions and cannot take your usual medicines by mouth.

Hospital care can include intravenous fluids, anti-sickness medication and monitoring. RCOG also advises that thiamine, a B vitamin, should be offered during hospital treatment, particularly when prolonged vomiting has affected normal eating.

The treatment that is appropriate for you should be decided with your healthcare team. Do not start, stop or change medicines based only on general information online.

Eating and drinking with HG

Advice that sounds simple during ordinary nausea can feel unrealistic when you have HG. If you are repeatedly vomiting or unable to keep fluids down, medical assessment matters more than trying to force yourself through a particular eating plan.

RCOG suggests that people who can manage some food may find small amounts of carbohydrate-rich, lower-fat foods or plain foods easier to tolerate. Avoiding foods and smells that trigger symptoms may also help.

Once symptoms improve, food and fluids can usually be built up gradually according to what you can tolerate.

If you cannot keep fluids down, are losing weight or are showing signs of dehydration, contact your healthcare team. Severe symptoms may need treatment rather than dietary changes alone.

Can hyperemesis gravidarum affect the baby?

RCOG says mild to moderate pregnancy sickness has not been shown to harm the baby. Severe nausea and vomiting or HG, however, can be associated with a baby having a lower than expected birthweight.

If severe sickness continues later in pregnancy, your maternity team may offer additional ultrasound scans to monitor your baby’s growth.

Individual circumstances vary, so your maternity team is the right place to discuss what monitoring may be appropriate for your pregnancy.

The emotional impact of HG

HG can affect much more than eating and drinking.

RCOG recognises that severe pregnancy sickness can affect mood, work, home life and social life. The NHS also notes that people with HG may feel anxious, isolated or unsure how they will cope if symptoms continue.

You deserve support for the emotional impact as well as the physical symptoms. Tell your midwife, GP or maternity team if you are feeling low, anxious or overwhelmed. They can discuss what support is available.

When to get professional advice

Contact your midwife, GP or maternity service as soon as possible if you are being sick frequently and cannot keep food or fluids down. The NHS advises seeking help because severe vomiting can lead to dehydration and weight loss.

Signs that you may be dehydrated include being very thirsty, feeling tired, dizzy or lightheaded, passing very little urine, or having dark yellow, strong-smelling urine.

RCOG advises contacting your GP or midwife if symptoms do not settle or stop you carrying out normal daily activities. Assessment may be needed, particularly if you cannot keep fluids or oral medicines down, have lost a lot of weight rapidly or have another medical condition that requires regular medication.

If vomiting begins for the first time after 16 weeks, or you have other symptoms such as abdominal pain or pain when passing urine, seek medical advice because other causes may need to be considered.

Contact your maternity unit for urgent pregnancy concerns. NHS 111 can advise if you cannot reach your maternity service or are unsure where to seek care. Call 999 in a life-threatening emergency.