Detailed explanation of the causes of morning sickness, its duration and how to deal with it【supervised by doctor】

Summary of this article

Morning sickness is a symptom of nausea and vomiting that occurs in the early stages of pregnancy and begins around the fifth week of pregnancy, with symptoms subsiding by the time the woman reaches the stable period, 16 weeks of pregnancy. Symptoms include nausea, vomiting, fatigue and sensitivity to smells. The mechanism causing morning sickness is not yet understood, but it is thought to be due to an increase in progestin levels, the effect of gas build-up in the body and hCG stimulating the vomiting centre.

What is morning sickness?

Morning sickness is nausea, vomiting and loss of appetite that occurs in early pregnancy. It starts around the fifth week of pregnancy and the symptoms settle down by the time you reach the stable period, 16 weeks of pregnancy. It is experienced by many pregnant women, and many of them realise they are pregnant because of morning sickness.

Typical morning sickness symptoms

The most common symptoms of morning sickness are nausea and vomiting. However, morning sickness varies widely from person to person and many other symptoms are known.

  • Nausea
  • Vomiting
  • Washed-out feeling
  • Excessive drooling
  • Feeling of a sticking throat
  • Intense drowsiness
  • Sensitive to odours

The causes of morning sickness are not known

Morning sickness afflicts many pregnant women. Medically speaking, it is called morning sickness and is a symptom of nausea and vomiting that occurs in the early stages of pregnancy. Morning sickness is said to occur in about 50-80% of pregnant women, but the symptoms and duration of morning sickness vary from person to person.

Generally, nausea and vomiting symptoms start to appear around the fifth week of pregnancy, with the most difficult period occurring around the tenth week of pregnancy. Thereafter, by the 13th week of pregnancy, morning sickness symptoms settle down and most pregnant women are over by the 16th week of pregnancy.

The mechanism by which pregnancy causes morning sickness is not understood. However, the following reasons are believed to cause morning sickness

  • Pregnancy increases progestin (progesterone), which causes gas to build up in the body, which in turn causes discomfort and nausea
  • Because hCG (human chorionic gonadotropin), which is produced and increased by pregnancy, stimulates the vomiting centre in the brain
  • The lack of vitamins and nutrients in the body due to pregnancy, which affects metabolism, blood sugar levels, etc

In particular, vitamin deficiencies have been reported to cause severe morning sickness symptoms, and it is recommended in the USA that adequate intake of vitamin B6 is taken during pregnancy. Vitamin B6 is said to help reduce nausea and should be taken with particular awareness during pregnancy.

In addition to hormonal and nutritional deficiencies in the body, morning sickness can also be caused by a disturbance of the autonomic nervous system due to stress caused by changes in the living environment and mental health due to pregnancy.

What is hyperemesis gravidarum?

Hyperemesis gravidarum is severe morning sickness with dehydration. Dizziness and day-long vomiting can often cause premature labour. It is difficult to distinguish it from severe morning sickness, but if there are abnormalities in blood or urine tests, fluids, electrolytes, vitamins B1 and B6, etc. should be replaced by intravenous fluids at an early stage.

Depending on the symptoms, hyperemesis gravidarum can damage the kidneys and liver, and there is a risk of complications such as pulmonary embolism and Wernicke’s encephalopathy. It is important to seek medical attention as soon as possible if there is severe dizziness, significant weight loss, or vomiting that is so severe that the woman cannot drink any fluids.

Are these early pregnancy symptoms? What is the relationship between pregnancy and early symptoms【supervised by doctor】
Uncover the mystery of early pregnancy symptoms and their connection with pregnancy, guided by expert insights from our ...

By common symptoms・How to deal with morning sickness

Although there are different types of morning sickness in different people, the following three are particularly common.

  • Eating sickness
  • Odour sickness
  • Vomiting sickness

Some people have only one of these symptoms, while others have a combination of several.


What is eating sickness?

Eating sickness is a form of morning sickness that causes nausea when hungry.

Symptoms of eating sickness

Nausea can occur when it has been some time since you have eaten, or when you are hungry just after waking up from sleep. As nausea increases with hunger, many people will deal with it by shoveling a bit of food into their mouths.

How to deal with eating sickness

Symptoms of eating sickness worsen when you are hungry, so it is important to avoid hunger as much as possible. Eating small amounts of food in several portions, or eating candy or gum instead of a batch of food, can help relieve the symptoms.

What should I do if I don’t want to eat?

Some people feel sick when they are hungry but feel nauseous if they eat. If you don’t want to eat but feel sick, try putting a little bit of candy, a rum, or chocolate in your mouth. Just a few mouthfuls may relieve nausea.

What should I do if I am hungry?

If you have eating sickness, you can eat without worrying too much about calories while you have morning sickness, as nausea increases as you get hungrier. Priority should be given to easing nausea and making you feel as comfortable as possible.

Foods to relieve morning sickness

Putting a few easy-to-eat foods in the mouth, such as candy, gum, gummies, crackers or chocolate, can help ease eating sickness. Ginger is another well-known food that can relieve morning sickness. Studies conducted in Australia have shown that consuming ginger can reduce symptoms of nausea and vomiting.

Effects of food intolerance on the foetus

Days of inability to eat due to morning sickness have little effect on the development of the foetus. This is because until around 16 weeks (five months) of pregnancy, the baby is nourished by the yolk sac.

The yolk sac is formed around four weeks into pregnancy and is responsible for sending nutrients to the baby. The baby is nourished from the yolk sac until the placenta is formed, so there is no need to worry about the foetus being affected by food intolerance.

Does stomach upset and queasiness cause stress?

Morning sickness can cause continuous stomach upsets and queasiness, which can be stressful for some. The food available to them changes from day to day, and many people are anxious about the fact that their body does not seem to belong to them.

Although the causes of morning sickness are not clearly known in some areas, it is said to be partly due to stress. Try to avoid stress by listening to your favourite songs or looking a little further afield.

When overeating and gaining weight

Some women gain weight due to increased calorie intake as hunger makes them feel sick. Weight gain in early pregnancy should be limited to about 3 kg, so there is no need to be overly concerned if you stay within this range.

However, excessive weight gain can put you at risk of having a giant baby. If you are concerned about your weight, chewing gum or eating calorie-free jellies can help to avoid excessive calorie intake.

Consult a doctor if stomach pain is severe

Some people have such severe stomach pain that they cannot eat as much as they would like. Try to chew your food well and eat foods that are gentle on the stomach, such as well-cooked vegetables and porridge. If the pain is really hard, consult your obstetrician/gynecologist. They can prescribe a stomach medicine that can be taken during pregnancy.

What to eat and what to watch out for during pregnancy and NIPT【supervised by doctor】
Discover essential tips on what to eat and be cautious about during pregnancy, including insights on NIPT, all supervise...

What is odour sickness?

Odour sickness is sickness that makes you feel sick when you smell certain odours.

Symptoms of odour sickness

The smell of cooking rice, the smell of the fresh fish section in the supermarket or the smell of fabric softener can cause nausea. Some women may only feel sick and not vomit, while others may vomit from the smell.

During pregnancy, the body becomes more sensitive to smells, so even smells that did not bother you at all before pregnancy can make you feel sick.

How to deal with odour sickness

The best way to counteract the smell is to avoid places where it occurs. If this is difficult, covering your nose with a handkerchief or wearing a mask may help.

Effects of odour sickness on the foetus

As for odour sickness, there is no concern that it will have a significant impact on the foetus. As long as you eat what you can eat, you should be fine.

What is vomiting sickness?

Vomiting sickness is morning sickness that makes you feel sick and vomit when you eat.

Symptoms of nausea and vomiting sickness

The most common symptom is vomiting when eating. The person may feel nauseous and vomit all the time, not just when eating.

How to deal with nausea and vomiting sickness

There is no need to eat unnecessarily when nausea is present. Keep hydration to a minimum with soda, vegetable soup or ionized drinks. Your obstetrician may be able to prescribe anti-nausea medication.

Let’s adopt a comfortable posture

Some people find it easier to lie down, while others find it easier to sit up. Changing posture may help relieve nausea, so try to find a comfortable position.

If you feel nauseous but cannot vomit

It can be difficult to feel nauseous but unable to vomit. Try drinking more water and eating foods that make it easier to vomit, such as udon, jelly or fruit.

Effects of nausea on the foetus

If you hardly eat at all due to vomiting sickness, you may worry about whether your baby is getting enough nutrients. However, the baby is nourished by the yolk sac until the placenta is formed, so not being able to eat is not said to have a significant effect on the baby.

If you vomit and lose weight

If you are vomiting and losing weight, the first thing to look out for is dehydration. If the nausea is so severe that you cannot even drink water, consider getting an intravenous drip from your obstetrician. If the mouth is dry or the skin is dry, you may be dehydrated.

If you lose weight without vomiting

Even if you are only nauseous and not vomiting, you may find it difficult to eat and lose weight. Losing weight and not gaining weight does not mean that the foetus will be affected. Try to drink fluids first, and see an obstetrician if you are dehydrated or significantly weak.

If there is diarrhoea

Persistent diarrhoea may lead to dehydration. If you are unable to drink water and experience thirst and dry skin, see your obstetrician for advice.

Does time of day matter for painful and distressing morning sickness?

Some people may experience waves of morning sickness at different times of the day. Morning sickness is known in English as ‘morning sickness’, which means that many people find the symptoms harder in the morning. However, the time of day when the waves come varies from person to person. Some people find it harder at lunchtime, while others experience the peak of the wave in the evening or at night.

When does the morning sickness period start? What is the peak?

Pregnant women may be very concerned about when painful morning sickness peaks.

Morning sickness starts around the fifth week of pregnancy

Generally, morning sickness begins around the fifth week of pregnancy. This is just about the time when you start to notice that your menstruation is delayed. However, morning sickness varies greatly from person to person, so some women start around the eighth week of pregnancy, while others have no morning sickness at all.

Morning sickness peaks around 8-10 weeks of pregnancy

Morning sickness generally peaks around weeks 8-10 of pregnancy. During this period, the secretion of hCG (human chorionic gonadotropin), which is also known to cause morning sickness, peaks and symptoms tend to be more severe.

Peak of eating sickness

Eating sickness also peaks around weeks 8-10 of pregnancy. After the peak, the nausea gradually eases and the morning sickness gradually comes to an end.

Peak of odour sickness

Similarly, odour sickness peaks around 8-10 weeks of pregnancy. However, some women say that the smell was bad until they had the baby, or that they had a bad smell for some time after the baby was born.

Peak of vomiting sickness

Nausea sickness is also characterised by a peak around the 8-10 weeks of pregnancy. After the peak, it gradually calms down, and by the time the woman enters the stable period, many of the symptoms will have eased considerably.

Detailed explanation of the causes of morning sickness, its duration and how to deal with it【supervised by doctor】

At Hiro Clinic, regular NIPT testing is available from the 10th week of pregnancy

NIPT is a test to check for chromosomal abnormalities in the baby. At Hiro Clinic, regular NIPT testing is available from the 10th week of pregnancy. Early NIPT can be performed as soon as a foetal heartbeat is confirmed by ultrasound. (However, it is currently recommended that a second NIPT test be performed after 10 weeks’ gestation if the pregnancy is before 10 weeks.)

The test requires only a blood sample and, unlike amniocentesis and chorionic villus tests, there is no risk of miscarriage.

It may be difficult to visit for the test if you have morning sickness, but you may want to consider it if you want to remove one of your concerns!

World-class NIPT
Experience unparalleled excellence in Non-Invasive Prenatal Testing (NIPT) at Hiro Clinic. Our world-class services blen...

What you can do to reduce morning sickness when it does not subside

Morning sickness that doesn’t subside, “How long is it going to last?” and can be physically and mentally depressing. Morning sickness is something you have to wait for to end, but there are a few things you can do to make it easier.

What the husband can do

Avoid strong-smelling foods and do what you can to help, such as preparing food instead or drying the laundry. Start by checking with your partner what they want you to do and what they don’t want you to do, as morning sickness varies greatly from person to person.

It is important that you both work together to get through morning sickness, such as buying food that you can eat or wiping yourself down if you can’t take a bath.

Clothing during morning sickness

Sensory sensitivity is common during pregnancy. Even if you are in the early stages of pregnancy and your belly is not noticeably distended, the tightness of clothes and belts can make you feel worse. During pregnancy, especially during difficult morning sickness, wear comfortable, loose-fitting clothes that feel good against the skin.

How to spend the morning sickness period

Morning sickness varies from person to person. Even pregnant women with less nausea and vomiting and milder morning sickness experience significant changes in their internal environment during pregnancy. It is important to stay physically active and stress-free in moderation.

Pregnant women with severe morning sickness do not need to force themselves to eat. There is no need to stress about not being able to eat, as normal morning sickness rarely affects the baby. Pregnant women with mild or severe morning sickness should first be calm, while being aware that morning sickness varies from person to person and that it has an end.


Morning sickness is said to be caused by progestin or hCG, which increases with pregnancy. However, the exact reason is not yet known. It generally starts around the 5th week of pregnancy, peaks around the 8th to 10th week and gradually eases off.

In the case of eating sickness, dividing meals into smaller portions and chewing gum may help to calm nausea. For odour sickness, try avoiding odour-sensitive areas or blocking odours with a handkerchief or mask. For vomiting sickness, try to drink at least a minimal amount of fluids, such as soda or ionic drinks.

Preparing food that you want and can eat can also be a great help.

Cooperation from your partner is also essential in overcoming morning sickness. Morning sickness with no end in sight can be tough, but you can cope and get through it.


Article Editorial Supervisor

Dr Hiroshi Oka

Dr Hiroshi Oka

NIPT specialist clinic, MD

Graduated from Keio University, School of Medicine


  1. 産後うつはいつからいつまで?
  2. 妊活中の食べ物は妊娠に影響する?
  3. 女性ホルモンとは


  1. 染色体異常の種類について