Morning Sickness During Pregnancy: Everything You Need to Know

Morning sickness raises lots of questions among new moms. When does morning sickness start? How long does it last? What causes nausea in pregnancy?

Today we are answering all your morning sickness FAQs and more, including:

  1. What’s normal,
  2. What causes morning sickness, and…
  3. What helps pregnancy nausea.

Morning sickness is very common, affecting 50-80% of all pregnant women. Armed with a bit of information about this less-than-fun aspect of pregnancy, it is our hope that you’ll find a little reprieve, even if it is simply in knowing that you’re not alone, and that you and your baby are healthy!

By: Dr. Tara Kelly, MD & Dr. Adam Brown

Morning Sickness FAQs

What is Morning Sickness?

Simply put, morning sickness is nausea experienced during pregnancy. 50% of women will experience this nausea to the degree that it causes vomiting or retching. Symptoms of morning sickness include nausea, retching, vomiting, weight loss, taste and smell aversions, and occasionally excessive salivation and spitting, known as hyperptyalism. Women may lose weight and even experience symptoms of depression related to ongoing nausea and its effect on quality of life. Many women need to take time off from work because of it. Morning sickness is one of the leading causes of hospitalization in the first trimester.

When Should I be Concerned?

A severe version of nausea and vomiting of pregnancy is known as hyperemesis gravidarum, which includes a loss of at least 5% of the prepregnancy body weight. Hyperemesis gravidarum can be associated with electrolyte abnormalities, severe dehydration, as well as a significant effect on the pregnant woman’s quality of life, both physically and psychologically.

Luckily, this hyperemesis only affects about 0.3 – 3% of all pregnancies and can be thought of as the extreme end of the spectrum of nausea and vomiting in pregnancy. Thankfully, most cases of this kind of severe morning sickness do not have serious effects on the baby.

When Does Morning Sickness Start?

Nausea and vomiting of pregnancy typically starts around 6 – 8 weeks of pregnancy, and always before nine weeks. Pregnancy sickness coincidentally coincides with the most developmentally vulnerable time for the fetus: during organ development.

How Long Does Morning Sickness Last?

While for most women nausea peaks around ten weeks of gestation and begins to abate around the end of the first trimester (13 weeks), it is also common for nausea to persist throughout the second or even third trimesters.

Tell Me More About Third-Trimester Nausea.

While morning sickness typically peaks around 10 – 12 weeks, it usually resolves after 20 weeks. In roughly 10% of women, however, nausea continues beyond 22 weeks.

New onset of nausea and vomiting in the second or third trimester though, if you’re not previously nauseated, could be a sign of other complications of pregnancy and should be discussed with your doctor.

Why is it Called Morning Sickness?

And no, it’s not mourning sickness, although you may feel like mourning as you experience it. Hang in there! This too shall pass.
“Morning sickness” gets its name from the fact that nausea is commonly made worse by an empty stomach, which is usually the case upon waking up in the morning. Interestingly enough, research reveals that less than 2% of women report morning sickness only occurring in the morning. Nausea and vomiting of pregnancy can occur at any time of the day: morning, afternoon or evening.

What Causes Morning Sickness?

What most people refer to as “morning sickness,” the medical community calls “Nausea and Vomiting of Pregnancy (NVoP).” The reason for this is that evidence is inconclusive as to the catalyst for those signs of sickness that correlate with (especially) early pregnancy.

Translation: several theories attempt to explain the symptoms of morning sickness.

The cause of morning sickness remains unclear. However, research has found several causal links. Because of this, it is commonly accepted that it is likely to be multifactorial—that many factors interplay with one another to cause a mother to feel nausea during pregnancy—and that various genetic, endocrine and gastrointestinal factors may be involved.

We’ve taken a close look at the most common possible causes for morning sickness. Here are five conventional theories, along with our researchers’ notes on why we find them all problematic.

5 Feeble Theories Behind the Cause of Morning Sickness

1. Progesterone and Estrogen

There is evidence that two specific hormones, progesterone and estrogen, can alter gastric rhythms and can induce gastrointestinal dysmotility.

Gastrointestinal dysmotility is a change in the way the muscles of the digestive system function. For example, the muscles of the esophagus often relax during pregnancy due to increased levels of progesterone. This allows food to make its way back up from the stomach more easily.

The Mommy Menu Take:

This theory is unlikely the main cause of morning sickness, given conflicting scientific evidence.

While there seems to be an association between gastrointestinal dysmotility and morning sickness, the association is controversial. Several studies report no difference in the gastric emptying rate between pregnant vs. non-pregnant control women. Other studies reveal no abnormalities in the timing of gastric emptying of women with morning sickness. Similarly, further studies showed no gastric emptying delay in the first, second, or third trimester.

2. Serotonin

Serotonin, another hormone and a neurotransmitter, is another theorized cause of morning sickness, the reason being that serotonin levels are reportedly higher in women who experience hyperemesis gravidarum (severe morning sickness).


The Mommy Menu Take:

This theory is unlikely the route cause of morning sickness, given conflicting scientific evidence.

If serotonin is a contributor to the causes of morning sickness, then one would expect that serotonin receptor antagonists would be superior to other medications at reducing nausea in pregnancy, yet the results reported in randomized control trials on the superiority of serotonin receptor antagonist over dopamine antagonists and antihistamines are still conflicting.

3. Helicobacter Pylori Infection

Helicobacter pylori is a germ that, if ingested, can deteriorate the lining of the stomach, leading to ulcers. It is an extremely common germ that can be ingested in the same way you would catch a common cold. Studies have tried to demonstrate a correlation between H. pylori infection and symptoms of morning sickness in pregnant women.

The Mommy Menu Take:

This theory is unlikely to be the cause of morning sickness.

Helicobacter pylori infection seems not to correlate with symptoms of nausea, vomiting or reflux during pregnancy. In fact, most women infected with Helicobacter pylori lack any of these symptoms.

4. hCG Levels

Of the above theories behind morning sickness, the human chorionic gonadotropin (hCG) hormone is most supported in medical literature, and perhaps most widely known.

What is hCG?

Human Chorionic Gonadotropin (hCG) – A human hormone made by chorionic cells in the fetal part of the placenta.

hCG is directed at the gonads and stimulates them. Hence, the name “gonadotropin.” It plays a role in the attachment of the egg to the uterine lining. Elevated hCG levels are an early indicator of pregnancy. In other words, when you take a pregnancy test, that little stick you pee on is on the lookout for hCG, since hCG levels increase within days of fertilization. hCG is thought to cause morning sickness because of the timing of both morning sickness and of hCG production, both of which peak between 12 and 14 weeks of gestation. There are additional links between this hormone and nausea. For example, nausea and vomiting are often worse in pregnant women with conditions associated with higher levels of hCG. Elevated hCG levels have also been discovered in women who experience morning sickness compared to those without morning sickness.
The Mommy Menu Take:

The hCG theory is also problematic.

While a multitude of studies link hCG and morning sickness, many other studies have found no relationship between hCG in pregnant women during the first trimester and the frequency or intensity of nausea and vomiting.

More importantly, studies have found that high levels of hCG are associated with intrauterine growth restriction and preterm delivery. This would be at odds with the research literature that reveals that, with increases in morning sickness, mothers are less likely to deliver prematurely.

For these reasons, it is unlikely for hCG to be the causal agent of morning sickness.

5. Genetic Predisposition
Yes, several extensive studies reveal that some individuals are more likely to experience morning sickness given their genetic background. But are genes enough of an explanation? While we do agree that genetic predisposition is likely a factor behind morning sickness, we at Mommy Menu believe there is more to the story.

The Mommy Menu Theory: Morning Sickness as a Defense Mechanism

While it is true that several theories attempt to explain NVoP (morning sickness), and that NVoP is probably dependent on a number of factors, researchers at Mommy Menu support a new theory behind the nauseating first trimester of pregnancy.

Nausea in Pregnancy = An Evolutionary Adaptation

Our theory is that the human body has evolved to detect teratogens, or substances that are harmful to a developing fetus, and remove them. After a teratogen has been detected, the body puts in motion a psychophysiological response that removes those teratogens before they can cross the placental barrier.

In this case, the definition of morning sickness is an evolutionary adaptation that evolved to detect and remove those ingested “toxins” to benefit the embryo or fetus; morning sickness may consist of smell and taste food aversions, nausea, and vomiting.

Through the lens of this theory behind morning sickness, nausea and vomiting during pregnancy play an incredibly important role–namely, that of protecting the fetus. It also would indicate that, rather than masking the evolved mechanism that is designed to protect the offspring with medications, avoiding teratogens is a more natural way of avoiding morning sickness.

How does a person ingest these harmful teratogens? Food, of course! By avoiding foods that are established teratogens and taking steps to ensure proper cooking techniques, mothers can reduce the body’s need for morning sickness!

Wait, My Body Needs Morning Sickness?

That is our theory.

Did you know that new moms commonly have smell and taste aversions to foods that have known teratology concerns (i.e., that could be harmful to a developing fetus)? As an adaptation, “symptoms” of morning sickness would be our evolutionary advantage simply functioning properly, identifying potential teratogens in food. As levels of the teratogens increase, a resulting nausea would warn the mother. Then vomiting is one physiological mechanism of removing the teratogenic culprit.

One way to avoid or reduce both nausea and vomiting would be to avoid those foods that contain teratogenic compounds. This happens to be our goal at Mommy Menu: to help pregnant mothers avoid dangerous substances that are commonly found in foods through our tracking app.

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Not Sold? Here Are 6 Points to Ponder

  1. The typical timetable for morning sickness coincides with organogenesis—the development of the baby’s organs. This is when the fetus is most vulnerable to disruption. If morning sickness is a defense mechanism to protect the fetus and mother from ingestion of toxic and teratogenic substances, particularly during the early stages of pregnancy, it makes sense that it happens at this time of the pregnancy. In this light, morning sickness benefits women by removing those foods that historically contain harmful toxins and microorganisms that could potentially sicken the woman and damage her fetus just when its organs are developing and are most vulnerable to chemicals and harmful bacteria.
  2. Similarly, nausea and vomiting decline after 18 weeks of pregnancy, as the fetus becomes less vulnerable to the effects of chemical disruptions.
  3. Studies over the past decade have found interesting evidence suggesting a possible benefit to experiencing nausea and vomiting during pregnancy. In a study of more than 95,000 women, those who experienced nausea and vomiting during pregnancy were less likely to deliver a baby preterm compared to women who did not experience any nausea or vomiting at all. This observed decrease in odds was even more dramatic for women who reported severe symptoms of vomiting and nausea.
  4. In another study that sampled more than 51,000 women, an associative relationship between nausea and vomiting and better fetal-birth outcomes was found, compared to women who did not have any symptoms.
  5. Sadly, but in line with the theory, women who experience no morning sickness are about three times more likely to miscarry spontaneously. On the other hand, women with the most severe morning sickness have lower rates of spontaneous miscarriage than other pregnant women.
  6. Psychological, sociological and cross-cultural research adds more evidence:
    • Historically, meats (because of fungal and bacterial decomposition) and bitter-tasting vegetables were likely to contain parasites, pathogens and plant toxins. These foods tend to both trigger more disgust in pregnant women and also reliably trigger morning sickness symptoms across cultures. Disgust and nausea are also triggered by alcohol and cigarette smoke, which also can harm the fetus while organs are forming.
    • Like the United States, societies that eat more meats, more bitter-tasting vegetables and consume more alcohol have higher rates of morning sickness than societies whose foods tend toward bland plant products.
    • Finally, and not to be dismissed, research reveals that several traditional societies report little to no morning sickness. These societies’ diets were investigated and were found to be based on bland, plant-based foods as opposed to meats and bitter tasting vegetables.
These findings support the hypothesis that women experience pregnancy sickness as an evolutionarily-derived adaptive response to toxins that could harm their growing embryos. In other words, when women ingest toxins or harmful microorganisms from their environment through the food that they consume, the body’s defense mechanism responds to rid of them of the agent to protect the baby.

Rather than unnecessary suffering, this theory gives a reason for the discomfort associated with early pregnancy. Morning sickness protects both the pregnant woman and the developing embryo, and does so when the fetus is most developmentally vulnerable.

What Helps Pregnancy Nausea?

Morning Sickness Remedies

  1. Prevention – One of the most effective strategies to prevent morning sickness is to be sure that you are taking a prenatal vitamin at least one month before conception.
  2. Dietary Changes – It is typically best to choose small amounts of food every 1 – 2 hours rather than large meals spaced apart. Limiting extra iron in the first trimester, and substituting folate for your prenatal vitamin may also help, though this should only be considered if approved by your OB. Some foods to avoid to help relieve nausea include fatty and spicy foods. A good approach is to choose bland, dry or high protein foods. The “BRAT” diet is often used when pregnant patients are admitted to the hospital with severe nausea. It consists of short periods of time where the diet is limited to bananas, rice, applesauce and toast.
  3. Ginger – Studies support the ingestion of ginger to help with relief of nausea in pregnancy, though there were no reductions of vomiting identified. The best choices are natural ginger sources—tea, fresh ginger—rather than ginger-flavored foods or drinks.
  4. Nonpharmacologic Treatments – There are no reliable studies that support the use of acupuncture, acupressure or nerve stimulation to reduce morning sickness. Despite that, some studies do trend toward showing a benefit, and there is no harm in trying any of these treatments in pregnancy. Any non-invasive method of improving your comfort during the first trimester is worth a shot!
  5. Nausea Medicine for Pregnancy – If no natural remedies for morning sickness seem to help, speak with your doctor about some of these medicines commonly prescribed for morning sickness:
    1. Vitamin B6 (pyridoxine) is the first-line treatment for NVoP, as recommended by the American College of Obstetricians and Gynecologist (ACOG). This is a safe supplement to use in pregnancy and may help reduce nausea, especially if started as soon as symptoms begin, if not earlier. The general dosing information is 25 mg every eight hours, though this can be confirmed with your doctor.
    2. Diclegis is a combination of Vitamin B6 and an antihistamine (doxylamine) and has been increasingly used to help pregnant women cope with the symptoms of morning sickness. The safety of this medication is well established in pregnancy, though it can cause drowsiness.
    3. Dopamine antagonists Reglan or Phenergan are effective at treating nausea and vomiting but may be associated with increased rates of maternal side effects such as drowsiness, dry mouth and dizziness.
    4. Zofran (Ondansetron) has been shown to be effective at treating nausea and vomiting, though a common side effect is constipation. *Note: There is insufficient evidence available regarding the safety of Zofran in pregnancy and more study is needed.
    5. Steroids have been used for severe cases of morning sickness (hyperemesis), but generally speaking, the side effects and risk profile here outweigh the benefit for most pregnant women.
  6. The Mommy Menu Approach – Simply take steps to avoid contact with or ingestion of teratogens! The most significant side effect of protecting baby and mom by reducing teratogen ingestion and contact is a reduction in morning sickness. A pretty nice side effect, right?

How to Reduce Morning Sickness, the Mommy Menu Way

At Mommy Menu, we have collected and continue to collect information from scientific literature and governmental sources to determine as many possible origins of toxins and teratogens for mothers, including chemicals naturally found in everyday foods, pesticides residing on the foods, food preparation techniques, cooking practices and more, all to protect your baby and you—the moms of the world—by informing and tracking.

The Mommy Menu app will help you avoid teratogens easily, once available on Google Play and App Store.

Be the First to Know When the Mommy Menu Tracking App is Ready for Download


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