In most cases, an unusual ammonia-like vaginal smell during pregnancy is caused by changes in urine. This can be due to lifestyle factors, such as dietary preferences, dehydration, and supplement use.

What a person eats and drinks during pregnancy can affect the smell of their urine. Sometimes, after using the restroom, small amounts of urine can remain on the outside of the vagina, causing it to take on the smell of urine.

Some infections, such as urinary tract infections (UTIs) and sexually transmitted infections (STIs), can also cause the vagina to smell odd or unpleasant.

There are several reasons why the vagina may smell like ammonia, including:

1. Increased nasal sensitivity

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The smell of urine can change during pregnancy due to a number of different factors.

Some pregnant women are more sensitive to certain smells, even in trace amounts.

This heightened sense of smell is called hyperosmia.

Ammonia is found naturally in the urine but does not usually give off a strong smell.

However, a pregnant woman may become more aware of a faint smell of ammonia that she did not previously notice.

Some researchers think women's nasal sensitivity increases during pregnancy to trigger nausea and vomiting, helping the mother to avoid digesting toxins that may harm the fetus, especially during the first few months of pregnancy.

Some limited research suggests that hyperosmia may be related to changes in circulating levels of the hormone human chorionic gonadotropin (hCG) during pregnancy.

2. Dietary changes

During pregnancy, many women experience cravings for foods they would not usually eat. Sudden dietary changes can cause the urine to smell different.

Certain foods contain nutrients and vitamins that may cause urine to smell like ammonia. These foods include:

  • asparagus
  • Brussels sprouts
  • garlic
  • onions

3. Vitamins and supplements

Many vitamins and supplements, especially those containing types of vitamin B, often cause changes in urine color and smell.

Pregnant women should always consult a doctor before taking new vitamins or supplements.

It is often best to increase the daily intake of foods rich in nutrients such as calcium, iron, and folic acid. Avoiding having to take unnecessary supplements can help reduce the risk of side effects and overdose.

4. Dehydration

When the body is dehydrated, the kidneys have less fluid available to dilute the urine, resulting in concentrated, stronger-smelling urine.

Many pregnant women experience some dehydration, especially before they know they are pregnant.

If a person does not drink plenty of water, the body will be unable to produce as much urine as usual. Urine will likely be darker than usual and might be bubbly.

5. Urinary tract infections

Around 8 percent of pregnant women develop urinary tract infections (UTIs), which can cause an ammonia smell.

Most UTIs are caused by bacterial infections, usually by a species of bacteria called Escherichia coli or E. coli.

Aside from the effects on odor, UTIs also cause:

  • painful or burning urination
  • sudden, intense urge to urinate
  • dark or cloudy urine
  • pelvic or lower abdominal pain

It is essential for pregnant women to talk with a doctor if they suspect they have a UTI because an infection can affect the growing baby.

The best way to stop the vagina from smelling like ammonia during pregnancy depends on the cause of the condition.

However, following some lifestyle tips may help reduce the likelihood, severity, and duration of the smell.

Easy ways to help prevent the vagina from smelling like ammonia include:

Practicing good hygiene

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Washing clothing and bedding regularly may help. Choose products that are suitable for sensitive skin.

Practicing good hygiene can help reduce the likelihood of developing infections and an ammonia-like smell. Tips for good hygiene include:

  • Changing and washing clothing and bedding regularly. Clean clothing is also less likely to contain trace amounts of urine, which may be more noticeable to pregnant women.
  • Wiping from front to back. Make sure to always wipe from the vagina toward the anus to reduce the spread of rectal bacteria and chance of infection.
  • Washing the genitals with plain soap and lukewarm water. Make sure the vagina is clean, but avoid exposing sensitive vaginal tissues to irritants found in scented body wash, vaginal deodorants, antiseptic products, and spermicidal products.
  • Avoiding douches and diaphragms. Douching and the use of diaphragms can irritate vaginal tissues and allow external bacteria to enter the urinary tract, spreading infection.

Staying hydrated

One of the easiest ways to stop the vagina from smelling like ammonia is to ensure that the body has enough fluid available to dilute the urine properly.

Drinking cranberry juice or apple cider vinegar

Many people believe that cranberry juice and apple cider vinegar can help acidify urine, which may help reduce its smell.

While cranberry juice has long been used as a home remedy for UTIs, there is no conclusive evidence that it is effective.

Urinating more often

The longer urine sits in the bladder, the more concentrated with uric acid it becomes. Holding in urine also gives bacteria time to multiply.

Urinating more often or before the urge to urinate occurs might help reduce the concentration and smell.

Eating probiotics

Probiotics are healthy intestinal bacteria. Eating foods rich in probiotics or probiotic supplements may help reduce the risk of bacterial UTIs.

Some research shows that probiotics found in fermented milk products, such as yogurt or kefir, may help prevent urinary infections and promote vaginal health.

Practicing safe sex

Sexual activity without using a condom or having multiple sexual partners increases the risk of developing conditions associated with urine that smells like ammonia. This includes UTIs and some sexually transmitted infections (STIs).

A vagina that smells like ammonia is rarely a sign of a STI.

However, some STIs are known to cause intense or foul-smelling urine, especially chlamydia. It is essential to get tested for STIs, as infections such as chlamydia often occur without symptoms.

Additional signs and symptoms of STIs associated with foul smelling urine include:

  • lower abdominal pain
  • vaginal discharge
  • painful urination
  • cloudy urine
  • painful, swollen labia or external genitalia

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Aspargus may make urine smell like ammonia.

If the vagina has an ammonia smell because of specific lifestyle factors, such as dehydration and dietary preferences, a person can make simple changes to reduce the odor.

Common tips for reducing ammonia-smelling urine include:

  • staying hydrated
  • avoiding foods that can cause urine to smell like ammonia, especially asparagus
  • limiting supplement or multivitamin use, especially those containing B vitamins
  • practicing safe sex
  • practicing good hygiene
  • urinating more frequently

Most UTIs and STIs are easily treatable with antibiotics if caught early enough. However, not all antibiotics are safe for pregnant women to take.

Penicillin and cephalosporin-based antibiotics are considered safe to take during pregnancy, while trimethoprim, fluoroquinolones, and sulphonamides should be avoided.

Most ammonia in the body is a by-product of the digestion of protein in the intestines. Millions of microbes, primarily bacteria, inhabit the intestines and help digestion.

After digestion, ammonia is taken up in the blood and drained into the liver where it is broken down into uric acid and glutamine, which are less toxic substances.

Uric acid then travels in the blood to the kidneys where it is diluted with water and expelled from the body in urine.

Ammonia is toxic and high levels of ammonia in the blood can cause symptoms including:

  • confusion
  • sleepiness
  • irritability
  • disorientation

High levels of ammonia may occur if the liver is unable to convert ammonia into uric acid, usually due to severe hepatitis or cirrhosis.

If left untreated, very high blood levels of ammonia can eventually cause difficulty breathing, seizures, coma, and death.

The vagina can smell like ammonia for a variety of reasons, especially during pregnancy.

The condition is typically harmless and associated with factors such as dietary changes and dehydration.

But if the vagina smells like ammonia for longer than a few days, or does not change with lifestyle changes, a woman should talk with her doctor.

Pregnancy is known to increase the likelihood of some conditions associated with unusual smelling urine, such as UTIs and STIs, which require prompt medical treatment.

While very rare, chronic ammonia-smelling urine can be a sign of severe medical conditions, such as kidney or liver failure.