The Bottom Line

Nausea and Vomiting of Pregnancy (NVP), or "morning sickness”, is the most common complication during pregnancy, affecting up to 90% of pregnant women to some degree. The entire condition is often underestimated and generalized among the general population. 

While it is true that some women will only experience mild NVP or none at all, it appears the vast majority of women suffer with moderate to severe NVP, which places a major burden on not only pregnant women, but their partners, families, and places of employment, as well as health care providers (HCPs) and facilities.

NVP is a very individualized condition; there are many possible causes of NVP in different combinations among pregnant women, with women experiencing a wide range of severities, contributing factors, and complications.

Women need to call their HCP if they are experiencing NVP they cannot control or manage effectively. Additionally, women should not be afraid to ask for help simply because they are not vomiting; nausea alone can result in complications.

Further, this needs to be done as early as possible. Numerous research studies have indicated that the earlier women engage in a conversation with their HCP, and the earlier they begin managing NVP, the more likely they can prevent symptoms from progressing to an unmanageable level – also preventing emergency department visits or hospitalizations.

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Background

"Morning sickness" is an outdated and informal term for Nausea and Vomiting of Pregnancy (NVP), the most common medical complication in pregnancy that affects up to 80% to 90% of women to some degree.

The symptoms and consequences of NVP can vary dramatically from woman to woman, from mild to completely debilitating (Hyperemesis Gravidarum) and from pregnancy to pregnancy in the same woman. The main symptoms can include only nausea, only vomiting (usually sudden), or both nausea and vomiting.

Based on average live birth data, 90% of pregnant women affected would translate to approximately 4.7 million women every year, combined, in the United States, Australia, United Kingdom, and Canada (90% of 4 million, 300,000, 650,000, and 350,000 live births each year, respectively).

Although NVP is mild in most cases, it can cause serious physical and mental complications, and should not be ignored or trivialized by family, friends, or HCPs simply because it can be mild, common, or “short-lived”. Further, NVP is not a psychological condition, but the exact opposite – women can experience serious mental health complications as a result of NVP.

Additionally, women with even mild NVP have reported experiencing the same psychosocial problems as women with severe symptoms, and severe symptoms are estimated to occur in up to 30% of women.

Women respond to NVP symptoms differently.

The way in which a pregnant woman responds to nausea/vomiting in early pregnancy depends on her tolerance and susceptibility to nausea, which is controlled by vestibular (motion), gastrointestinal (GI tract), olfactory (smell), and behavioral (brain) pathways, as well as real, physical contributing factors already brought on by pregnancy. Further, a woman’s threshold for nausea may also change minute-to-minute depending on these factors.

Nausea

A common definition of nausea identifies it as a precursor to vomiting, but with NVP, nausea does not always mean vomiting is inevitable, and only about 50% of those who experience NVP will actually vomit. It is also possible – although less frequently – to experience vomiting without nausea. This can occur because nausea and vomiting are partially separate physiological processes.

Nausea can be constant as well as sudden, triggered by smells, sights, textures, temperatures, and movement. During early pregnancy, the stimuli that initiate nausea and vomiting in the body are incredibly sensitive; therefore, it does not take much to suddenly feel or become ill without warning.

Unfortunately, in general, most individuals report that nausea is more common, more disabling, feels worse, and lasts longer than vomiting. Further, nausea is much more difficult to treat than vomiting. Suffering through nausea for weeks on end is exhausting, frustrating, and mentally draining; women can find it very difficult to cope.

Women's experiences with nausea during early pregnancy can vary, from not feeling nauseous at all to feeling nauseous 24-hours a day.

Vomiting

The differences between pregnant women with only nausea, both nausea and vomiting, or only vomiting (no nausea in between) are not understood, and researchers do not know why some women vomit with NVP while other women do not.

Although rates of vomiting with NVP varies widely, one study indicated that half of surveyed women (who vomited at all) reported vomiting at least once a day, and 13% reported more than three vomiting episodes daily. On average, vomiting episodes occurred about three days each week.

Frequent vomiting during NVP (three or more times per week) can damage taste receptors and increase the presence of stomach acid in the mouth, which alters the ability to taste salt, sweet, bitter, and sour flavors, further inhibiting the ability to eat through the condition.

Vomiting also increases the risks of additional complications, such as dehydration, electrolyte imbalance, gastrointestinal irritation, and tooth decay (read Complications).

Further, frequent vomiting can be very traumatic. Women have reported that pain experienced during vomiting with NVP was worse than the pain experienced during labor, and for some women, the mental anguish from this experience can sometimes last years after delivery.

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Timing

The term “morning sickness” was reportedly used for the first time in 1803 and has therefore had more than 200 years to stick. A study published in 1918 added weight to this term and indicated the majority of “morning sickness” cases occurred in the morning, disappeared during the day, and returned the next morning, perpetuating the misbelief that an empty stomach was the sole responsible factor.

Researchers now know that up to 80% of women experience all-day symptoms, while less than 2% report symptoms that occur only in the morning. In addition, eating usually does very little to relieve symptoms, especially when severe. Eating, may however, work in women in whom an empty stomach is a contributing factor.

Symptoms usually begin around 4 to 6 weeks of pregnancy, with about 20% of women reporting symptoms before a positive pregnancy test.

Women may begin to experience NVP symptoms as early as 11 to 20 days after ovulation.

A study published in January 2021 indicated NVP symptoms likely begin a lot earlier than previously thought, as more than half of the study participants experienced symptoms between 11 and 20 days after ovulation.

The study further noted that the close connection between onset of NVP symptoms and date of ovulation reinforces the theory that the cause of NVP is biological, not psychiatric, and is likely based on a very specific window of fetal development (Gadsby et al. 2021).

It is estimated that only about 50% of NVP cases resolve by 14 weeks, and 90% by 22 weeks. Up to 10% of women will experience symptoms beyond 22 weeks, to include up until delivery. Symptoms that continue up to 16 to 18 weeks before completely improving is considered normal

However, due to the misconception that NVP usually relieves around 12 weeks, women can experience significant frustration and disappointment at the continuation of symptoms beyond this time.

Another review indicated NVP symptoms are estimated to last an average of five to eight weeks (35 to 56 days). However, some pregnant women may experience NVP for only just a few days, while others won’t experience it at all.

Based on all averages mentioned above, if a woman starts experiencing NVP symptoms around 5 weeks of pregnancy, experiences mostly all-day symptoms, and does not get full relief of symptoms until about 18 weeks, that equates to about 13 weeks of nausea and/or vomiting to some degree (more than 3 months). 

The effects of NVP are compounding and progressive. The longer a woman experiences NVP without adequate support from family/HCPs, the higher the risk for complications.

Symptoms and Complications

NVP is more encompassing than nausea and vomiting. Both of these symptoms can lead to complications such as extreme fatigue, dehydration, acid reflux, headaches, dental issues, trouble sleeping, weight loss, malnutrition, electrolyte imbalances, and hospitalization, as well as anxiety and depression.

NVP also occurs simultaneously with other uncomfortable early pregnancy symptoms, and NVP can also cause many others. This is also why unmanaged NVP can sometimes spiral quickly, which leaves women feeling like nothing is working.

Read Symptoms and Complications for more detailed information.

Causes – Overview

NVP is currently assessed to be multifactorial – caused by more than one factor at the same time, some of which can also be considered contributing factors.

On top of the "standard" causes of NVP, there are many normal changes during early pregnancy that can contribute to NVP and make it worse (acid reflux, fatigue, lack of sleep), to include conditions in a woman’s own medical history.  

Therefore, women can experience a different combination of these factors, depending on their sensitivity to hormones, motion, GI tract changes, taste and smell preferences, as well as the presence of certain risk factors, genetics, and underlying conditions.

This is also assessed to be the reason that researchers cannot find one primary, consistently effective medication or management technique for all women with NVP. Depending on why each individual woman is experiencing symptoms and what may be contributing to it, women are going to find many different effective strategies.

While one woman may find success with ginger, crackers, or acupressure, those may not even touch the symptoms of another woman. Further, while one woman may find very effective relief with vitamin B6, another woman may not.

For example, if one woman has a history of being nauseous with oral contraceptive pills, and she experiences NVP, a sensitivity to hormones is her likely cause of NVP.

If another woman had no issues with oral contraceptives, and has severe NVP, her cause(s) are most likely different – it could be reflux, gastrointestinal changes or severe fatigue. She could also have a history of migraine headaches or motion sickness, which makes her very sensitive to central nervous system stimulation that occurs during pregnancy.

Some women – even with severe NVP, find almost complete relief from antacids, illustrating acid reflux as a possible primary cause of NVP, which surprises most women. However, these medications are not effective in women not suffering from some form of reflux.

HCPs can help women determine possible causes of their NVP as well as possible contributing factors. This makes a woman's medical and obstetric history very important, so HCPs can evaluate women's risk factors and attempt to match these factors to an individualized management plan.

Read Causes and Contributing Factors for more information.

Risk Factors

While specific risk factors for NVP are formally recognized, they are conflicting and not considered well-established, as many women without these risk factors may also experience NVP . However, these risk factors can be useful in helping women prepare for an increased possibility they could experience more severe symptoms.

A study published in July 2020 identified an association between a personal history of nausea in various situations and the severity of NVP, indicating that factors behind NVP may stem from similar factors as nausea and vomiting in general for some women.

Some of these factors appear to include a history of motion sickness and migraine headaches, which could indicate a hypersensitivity toward nausea based on vestibular (motion/balance) triggers.

Women who experience nausea when taking estrogen-containing oral contraceptives also appear to be at an increased risk for NVP (sensitivity to hormones).

Women with mothers and/or sisters with NVP may be more likely to experience NVP in their own pregnancies (genetics). However, plenty of women without a family history will experience NVP.

Women with a history of NVP in a previous pregnancy are more likely to experience it in subsequent pregnancies, but this is also very inconsistent across studies. NVP, including hyperemesis gravidarum (HG) is highly unpredictable in the same woman across different pregnancies. There is no definitive way to determine if a woman will experience NVP in future pregnancies, whether at the same severity, worse, or even at all.

An increased risk of NVP has also been reported in women carrying more than one baby, assessed due to higher human chorionic gonadotropin (HCG) levels in the blood. However, HCG is falling out of favor as the main risk factor in current research (read more).

Other risk factors include first pregnancies, expecting a girl, certain fetal abnormalities (such as Down Syndrome), and trophoblastic disease (molar pregnancy), likely due again, in part, to higher HCG levels. Studies evaluating these risk factors are also inconsistent, especially expecting a girl.

It is possible that marijuana use before pregnancy is related to an increased risk of NVP. Women who stop using marijuana after learning they are pregnant (as opposed to before) may experience nausea and vomiting due to withdrawal (which is also mistaken for NVP).

Although inconsistent, risk factors do have utility for NVP .  Even though the presence of risk factors does not necessarily mean a woman will experience NVP or severe NVP , it can help women prepare for it ahead of time. Preparation and early management are very important in the prevention of more severe NVP .

Management

Current research has not found one particular lifestyle change, dietary modification, or medication that can be considered most effective at treating all women, with the causal factors described above as the likely explanation for this.

When NVP research is performed and published, women are all assessed and grouped together when reviewing the effectiveness of various foods, lifestyle changes, or medication – despite women's unique causal, risk, or contributing factors. This is likely playing a part in the vastly inconsistent conclusions regarding the effectiveness of various management techniques.

Medications and other strategies should be assessed in women who appear to have the same risk factors, underlying conditions, or contributing factors of NVP. This would allow researchers to try to formulate possible treatment plans for women based on these factors, rather than trying to find one medication or one strategy that will treat all women experiencing NVP (read more). Additionally, most of these factors may be easily identified by an HCP in an office setting.

Therefore, NVP management needs to be specifically tailored to each individual woman, after a detailed medical history, physical assessment, and risks and benefits discussion with her HCP. 

Further, and despite the above, women can still have adequate control over their symptoms in most cases. Updated and correct knowledge of NVP  – its durationseveritycauses and contributing factorsrisk factorspossible complications, latest management methods, and resulting preparation – can help women, their partners, and their family members manage not only their expectations, but the woman’s physical, mental, social, and emotional health as well (and the family's overall adjustment).

Of most importance, women need to find an HCP who fully understands NVP, empathizes with women who are experiencing it, and takes the time to manage all aspects of the woman's health,

Read Management Introduction for more information.

Mental Health Impact

NVP can significantly affect a woman’s mental health and overall quality of life.  Women tolerate nausea differently. Some women can handle six weeks of nausea without much consequence, while others may break down after a week or even a day. Every woman is different, and every woman requires adequate support.

The effect of NVP on a woman’s quality of life depends on her support system, her employer, whether she takes care of other family members, her day-to-day responsibilities, as well as the severity of her symptoms and many other factors.

Fighting nausea weeks on end is physically draining, mentally challenging, and utterly stressful when relationships become strained during the process. Even when there is whole and complete understanding among family and friends, frustration can occur when no one knows what to do or how to help.

NVP – especially HG – can be traumatic and lead some women to experience posttraumatic stress symptoms, as well as signs as of anxiety and depression, sometimes years later. Some studies have reached this conclusion even with mild and moderate cases.  A lack of recognition of the condition by family, friends, and HCPs can compound these issues.

Read Mental Health for more information.

Economic Burden

The effects of NVP are not limited to pregnant women. NVP can result in financial hardship for women's families, their places of employment, and the health care system.

In the United States, the conservative estimated total economic burden for NVP management in 2012 was estimated to be more than $1.7 billion; the average cost to manage one woman for NVP was $1,827.

Hospitalization costs are estimated to be approximately $47,351 per HG patient. HG is the most common reason for hospitalization in early pregnancy and second only to preterm labor throughout the whole of pregnancy.

In the United Kingdom (U.K.), the annual cost of NVP and impact to the U.K. National Health Service was estimated to be up to £62,373,961, and around 8.6 million hours of paid employment lost due to NVP.

In Canada, data collected from 139 pregnant women indicated the total cost per woman per week was $132, $355, and $653 for women with mild, moderate, and severe NVP, respectively.

It is further estimated that 206 work hours are lost for each employed woman with NVP , and about a quarter of women may experience impaired job efficiency. NVP accounts for about 28% of all sick leave during pregnancy before week 28, and before maternity leave. Some women with severe NVP /HG can be absent from work their entire pregnancy.

However, employers can provide women reasonable accommodations to help mitigate this loss of productivity, especially for women who need or want to work (read more).

Action

The first major point of action for pregnant women is to call their HCP if they are experiencing NVP they cannot control or manage effectively

Note: Women should not be afraid to ask for help simply because they are not vomiting; nausea alone can result in complications.

Further, this needs to be done as early as possible. Numerous research studies have indicated the earlier women engage in a conversation with their HCP, and the earlier they begin managing their nausea/vomiting, the more likely they can prevent symptoms from progressing to an unmanageable level, thereby preventing severe complications.

Women should also learn as much as they can about NVP to better understand management strategies and why and when they are recommended. 

Women should consider sharing their NVP experience (below), especially how they felt, how long it lasted, what may have caused or contributed to their symptoms, and anything they did that relieved symptoms, even if only temporarily.

This can be a very difficult few weeks/months for women. Reading experiences of other women can help them better mentally cope and manage their symptoms and teaching them to be a better advocate for themselves at home, at work, and at their HCP's office.

Partners/Support

Partners of pregnant women, along with family members who support them, need to understand this condition is real and can be utterly debilitating in some cases.

NVP is fluid, can change in severity quickly, and can last for months. Women experiencing these symptoms need help – the most important of which – is simply recognition.

A true team effort can show women with NVP they are supported, and their symptoms are recognized.  Women need people in their corner who are listening to them and taking proactive steps to help them manage their condition to preserve not only their physical and mental health, but the joy and excitement of their pregnancy.

Partners/support should also do their part by learning everything they can about the condition, just like a pregnant woman. When women and their partners/support are working off the same page, women feel more supported, more understood, less frustrated, and have an additional resource they can count on when symptoms get too difficult to manage on their own.

Resources

Nausea and Vomiting of Pregnancy: Committee Opinion 189; January 2018 (American College of Obstetricians and Gynecologists)

Morning Sickness: Nausea and Vomiting of Pregnancy (American College of Obstetricians and Gynecologists)

Pregnancy sickness (nausea and vomiting of pregnancy and hyperemesis gravidarum) (Royal College of Obstetricians and Gynecologists)

References

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