Can Boric Acid Cause Miscarriage?

If you’re pregnant and find yourself endlessly scrolling through online forums, you’re not alone. Not by a long shot.

With so many dos and don’ts in pregnancy, it’s understandable if you’re not totally sure what’s what. But there’s one question in particular that we’ve seen come up a lot: Can boric acid cause miscarriage?

According to OB/GYN Cordelia Nwankwo, MD, FACOG, “There is no data showing an association between boric acid and risk of miscarriage.” But that doesn’t make boric acid safe for pregnancy.

There’s also mixed evidence that another fluconazole (Diflucan), another commonly used treatment for yeast infections, may increase the risk of miscarriage. But, to our knowledge, there is no comparable research investigating the link between boric acid and miscarriage.

And that gap matters. A lack of miscarriage-specific data doesn’t equal a green light. It often means the question hasn’t been studied well enough, especially in pregnant populations where ethical limits make research harder to run. What we do know is that major medical organizations advise against using boric acid during pregnancy due to potential toxicity and unknown fetal effects. The CDC also excludes boric acid from its recommended treatments for vaginal infections during pregnancy, favoring options with established safety profiles instead.

Here, we’ll break down what boric acid is, what the research actually shows and doesn’t show, and how to think about risk when the science is incomplete. Because when it comes to pregnancy, “we don’t know” should still be handled with care, not assumptions.

What is boric acid?

Boric acid is a white power used in hundreds of over-the-counter products, from soil fertilizers to personal care products. It’s derived from the natural element boron. Boric acid’s use in a wide array of products stems from its antifungal and antimicrobial properties.

Boric acid suppositories are an over-the-counter treatment that can help with yeast infections and bacterial vaginosis (BV). When the balance of “good” versus “bad” bacteria in the vagina is thrown off, this also disrupts the vagina’s acid balance. Boric acid suppositories work by adjusting the vagina’s level of acidity.

Although boric acid suppositories have demonstrated effectiveness for treating vaginal conditions, they’re not FDA-approved because they’re supplements. This means there’s no way to know for sure that every boric acid suppository is as effective as others.

Zooming out a bit, boric acid has been used for well over a century in medicine and industry. Historically, it showed up as a mild antiseptic and preservative before modern antibiotics and antifungals existed. Today, its role is much more specific. You’ll still see it in household products, insect control, and cosmetics, but in vaginal care it’s typically reserved for recurrent or hard-to-treat infections when standard treatments haven’t worked.

That said, “widely used” doesn’t automatically mean “universally safe.” The National Pesticide Information Center notes that boric acid can be toxic if swallowed in large amounts or used improperly, which is why dosing, formulation, and route of exposure matter so much, especially during pregnancy.

Understanding what boric acid is and how it works sets the stage for the bigger question. When you’re pregnant or trying to be, safety depends not just on whether something works, but on what we know and don’t know about its risks.

Boric acid suppositories for vaginal health

Boric acid suppositories are most commonly used to support vaginal health when infections keep coming back or don’t respond to first-line treatments. They’re inserted vaginally and work by changing the vagina’s pH. A healthy vagina is naturally acidic, and when that balance shifts, yeast or bacteria can grow more easily. Boric acid helps restore that acidic environment, making it harder for unwanted microbes to thrive.

Clinically, boric acid suppositories have been studied primarily for recurrent yeast infections and recurrent bacterial vaginosis (BV). A 2023 randomized comparison study for the Egyptian Journal of Hospital Medicine found that boric acid was effective in treating azole-resistant yeast infections, with reported cure rates of around 70% in small clinical studies, particularly when standard antifungal medications had failed. UpToDate, a widely used physician reference, also notes boric acid as a potential option for recurrent BV when conventional therapies haven’t worked, though it emphasizes careful patient selection and counseling.

You can buy boric acid suppositories over the counter, which often makes them feel like a low-risk, DIY solution. But here’s the important nuance. These products are classified as supplements, not medications. That means they’re not FDA-approved, and manufacturers don’t have to prove safety, effectiveness, or consistency before selling them. Supplement products can vary widely in dose and formulation, even when they appear similar on the shelf.

That variability matters. Different brands may contain different amounts of boric acid, dissolve differently, or include additional ingredients that haven’t been well studied. While some people find them helpful under medical guidance, others experience irritation or worsening symptoms.

And when pregnancy enters the picture, the lack of regulation and safety data becomes even more relevant. Effectiveness for vaginal infections does not automatically translate to safety for a developing fetus, especially when absorption through vaginal tissue is possible. That’s why understanding how these suppositories work and how loosely they’re regulated is a key part of evaluating their role during pregnancy.

Is boric acid safe during pregnancy?

The American College of Obstetricians and Gynecologists (ACOG, the leading body of OB/GYNs) advises against using boric acid vaginal suppositories during pregnancy. This is because human data, although limited and often poorly collected, shows a possible association between boric acid and fetal malformations or defects. In animal data, high levels of boric acid taken orally have been linked with adverse fetal outcomes. There are no similar studies for intravaginal boric acid use in pregnant animals.

So, while the jury is out on the exact effects of boric acid use in pregnancy, the safest path is to follow ACOG’s guidelines and avoid it altogether.

That doesn’t mean one accidental use automatically equals harm. It means we do not have reassuring, high-quality pregnancy safety data, and there are enough red flags (including teratogenicity at high oral doses in animal studies) that a better-safe-than-sorry approach makes sense. A 2021 narrative review published in Sexually Transmitted Diseases lays this out clearly: pregnancy guidance is cautious because human evidence is limited and messy, animal data at high oral exposures shows developmental toxicity, and we do not have pregnant animal studies for intravaginal exposure to fill in the gaps.

If you’re dealing with BV or a yeast infection while pregnant, there are options with more established safety profiles. The CDC’s 2021 STI Treatment Guidelines recommend pregnancy-compatible regimens for BV and vulvovaginal candidiasis, and boric acid is not a go-to choice during pregnancy.

Important note: Taking boric acid orally can be very dangerous, whether you’re pregnant or not. Never take boric acid orally.

Can boric acid affect early pregnancy?

Early pregnancy is the most vulnerable window because so much is being built so fast. Organ development (organogenesis) is happening mainly in the embryonic period, which is roughly weeks 3 through 8 after fertilization. That’s why many teratogen discussions focus on first-trimester exposures, especially before someone even knows they’re pregnant.

So if boric acid were to pose a developmental risk, the first trimester is the time we’d be most concerned about, even though we do not have clean, direct miscarriage data to point to.

What happens if you use boric acid while pregnant?

If you used boric acid and then found out you were pregnant, take a breath. Most single, brief exposures do not automatically translate to a bad outcome, and panic is not a plan. The reality is that the biggest issue here is uncertainty: we can’t quantify the risk well, which is why experts recommend avoiding it once pregnancy is known or suspected.

Why can't you use boric acid while pregnant?

Because pregnancy is one of those times when “it probably won’t hurt” is not the standard we’re aiming for. With boric acid, the potential downside is fetal development, and the upside is treating a vaginal infection with a product that has safer, better studied alternatives in pregnancy. That’s why most reputable guidance lands on the same answer: avoid it.

Here’s what’s driving that caution:

There are signals of developmental risk, even if the human data is limited.

A 2021 review in Sexually Transmitted Diseases summarizes why multiple guidelines, including ACOG, recommend avoiding intravaginal boric acid in pregnancy. The authors note that human pregnancy data is sparse and not great quality, but it raises concern for teratogenic effects, and that’s enough to warrant a conservative approach.

Animal studies show harm at high oral doses, and we can’t cleanly translate exposure.

In toxicology studies, high oral boric acid exposure during pregnancy has been linked to adverse fetal outcomes (like growth restriction and malformations). For example, a 1996 rat study published in Fundamental and Applied Toxicology reported developmental toxicity with gestational boric acid exposure, including fetal growth effects and skeletal changes.

And a 1996 rabbit study published in Toxicological Sciences found higher malformation rates at the highest dose group, driven largely by cardiovascular defects.

Important context: these were oral doses at levels much higher than typical OTC vaginal use, but they still raise a “we should not gamble here” flag.

We don’t have the specific safety testing we’d want for vaginal use in pregnancy.

The same 2021 review points out a key gap: there are no comparable studies looking at intravaginal boric acid use in pregnant animals, and absorption could vary if vaginal tissue is irritated or inflamed. Translation: we can’t confidently say what fetal exposure looks like.

The benefit usually isn’t worth the uncertainty in pregnancy.

Boric acid can be helpful for some stubborn infections in non-pregnant people, but pregnancy isn’t the time for experimental-ish solutions. The CDC’s STI Treatment Guidelines outline pregnancy-compatible treatments for yeast infections and BV, and boric acid is not positioned as a pregnancy option in those recommended regimens.

OTC does not mean “FDA approved for pregnancy.”

Many boric acid suppositories are sold OTC, often as supplements or similar non drug products. The FDA’s own consumer guidance explains that the FDA does not approve dietary supplements for safety and effectiveness before they’re sold, and companies are responsible for product quality and safety. That’s a problem when you’re pregnant because dose and formulation consistency can vary, and pregnancy safety data is not required up front.

Separately, the 2021 review also notes intravaginal boric acid is not an FDA-approved drug and is widely available OTC.

Putting it all together: ACOG’s stance + limited human evidence + developmental toxicity at high doses in animals + major research gaps equals a clear “no thanks” during pregnancy. It’s not about shaming anyone for trying to feel better, it’s about choosing the option with the most reassuring safety track record when there’s a tiny human in the mix.

Can boric acid affect implantation or fertility?

Right now, there’s no good evidence that boric acid vaginal suppositories cause long-term fertility problems or directly interfere with implantation. The bigger issue is that this specific question just hasn’t been studied in a clean, reassuring way.

The 2021 narrative review in Sexually Transmitted Diseases looked at the safety data on intravaginal boric acid and noted something important: the authors couldn’t find literature on fertility effects from intravaginal boric acid use. In other words, we don’t have evidence that it harms fertility, but we also don’t have robust data that proves “no impact,” especially for people actively trying to conceive.

What we do know is that boric acid suppositories are designed to shift vaginal acidity. Boric acid vaginal suppositories help promote a balance of acid in the vagina. That matters for TTC because sperm are sensitive to pH. In a 2015 study in PLOS ONE, human sperm motility dropped in more acidic conditions (lower pH).

And in a 2000 study in Fertility and Sterility, when semen was acidified to a very low pH (pH 4.0), sperm were rapidly immobilized and then irreversibly immobilized within minutes.

So, could boric acid indirectly make conception harder in the short term if you use it right around sex? Possibly, because it can change the environment sperm move through. But that’s not the same thing as “it affects implantation,” and it’s not the same thing as “it causes infertility.”

One more nuance: a lot of scary fertility data about boric acid comes from high-dose oral exposure, mostly in animals. Reviews of boron compounds describe dose-related testicular toxicity and sperm effects in animal studies, which is very different from using a standard vaginal suppository as directed.

Does boric acid kill sperm?

It’s more accurate to say it may reduce sperm movement or survival temporarily by altering pH, rather than acting like a reliable spermicide. The pH data above shows sperm don’t love acidic environments.

Timing considerations if you’re TTC: If you’re trying to conceive, it’s reasonable to avoid boric acid suppositories during your fertile window and instead talk to your clinician about TTC friendly treatment options for yeast or BV. Also, boric acid is not a contraceptive method, and you should not rely on it to prevent pregnancy.

Boric acid while breastfeeding: Is it safe?

Short answer: we don’t have enough good data to say boric acid is clearly safe while breastfeeding, so most guidance leans toward caution.

There’s very limited research looking specifically at boric acid vaginal suppositories during lactation. According to Infant Risk Center at Texas Tech University Health Sciences Center, boron (the element boric acid is derived from) can be absorbed systemically, and small amounts may pass into breast milk. What we don’t know is how much transfer happens with vaginal use, or what level could pose a risk to a nursing infant. That uncertainty is the problem.

Because of that gap, many clinicians recommend avoiding boric acid while breastfeeding unless there’s a clear medical reason and no safer alternatives. This mirrors the cautious stance taken during pregnancy. The American College of Obstetricians and Gynecologists generally advises prioritizing treatments with established safety data in pregnancy and lactation, especially when managing common vaginal infections that have other options.

If you’re breastfeeding and dealing with recurrent yeast infections or BV, it’s a good idea to talk to your healthcare provider before using boric acid. There are lactation compatible treatments recommended by the CDC for both conditions, and your provider can help you choose an option that treats symptoms without introducing unnecessary uncertainty.

One accidental or short use while breastfeeding doesn’t mean harm is guaranteed, so there’s no need to panic. But because infant exposure hasn’t been well studied, most experts recommend choosing alternatives with a clearer safety track record while nursing and looping in your clinician before starting or restarting boric acid.

Safe alternatives to boric acid during pregnancy

Some vaginal infections, like bacterial vaginosis (BV), may increase the likelihood of preterm labor. While yeast infections aren’t likely to impact pregnancy or birth outcomes, they’re uncomfortable regardless of pregnancy. Thankfully, some medications are safe to take during pregnancy for both conditions.

Dr. Nwankwo recommends that her pregnant patients take metronidazole (aka Flagyl) orally or vaginally for BV. For pregnant patients with yeast infections, she recommends over-the-counter or prescription azole creams (e.g., Monistat 7-Day Treatment).

Metronidazole is considered a first-line treatment for BV in pregnancy, with guidance from the CDC supporting both oral and vaginal use. Large observational studies haven’t found an increased risk of miscarriage or birth defects, even with first-trimester exposure. Treating BV matters because leaving it untreated has been linked to higher risks of preterm birth and other complications later in pregnancy.

For yeast infections, topical azole antifungals like miconazole or clotrimazole are the preferred option during pregnancy, especially 7-day treatments rather than single-dose oral meds. Research shows no association between topical azoles and miscarriage, congenital anomalies, or preterm birth, and because they work locally, fetal exposure is limited.

In some cases, providers may also suggest clindamycin vaginal cream for BV or prescription-strength azole creams if OTC options don’t help. The takeaway is simple: get an accurate diagnosis and treat it with options that have pregnancy safety data. Pregnancy isn’t the time to guess, but it is the time to prioritize both comfort and prevention.

Can yeast infections or BV cause miscarriage?

BV has been associated with adverse pregnancy outcomes, particularly preterm labor, rather than early miscarriage. A 2019 review published in Scientific Reports found a consistent association between BV and preterm birth, which is why treatment is recommended during pregnancy.

Yeast infections, on the other hand, generally do not increase the risk of miscarriage or poor pregnancy outcomes, according to information by MotherToBaby. Treatment is still important for comfort and to rule out other causes of symptoms, especially if pain, bleeding, or fever are present.

Can Monistat or other alternatives cause miscarriage?

Current evidence does not show that recommended pregnancy treatments like azole creams or metronidazole increase miscarriage risk. Multiple cohort studies and reviews have found no association between topical azole antifungals and pregnancy loss.

Metronidazole has also been extensively studied. Information published by MotherToBaby in 2024 found no increased risk of miscarriage, birth defects, or preterm birth associated with its use.

It’s normal to worry about taking any medication during pregnancy. But avoiding treatment altogether can sometimes carry more risk than using options that have been studied and recommended by major medical organizations. If something doesn’t feel right, or symptoms are worsening, that’s your cue to check in with your healthcare provider and get guidance tailored to your pregnancy.

What to do if you used boric acid before knowing you were pregnant

First, take a breath. A single or brief use of boric acid before you knew you were pregnant is unlikely to cause harm. Most recommendations to avoid boric acid are based on limited safety data, not clear evidence that short early exposure causes miscarriage or birth defects.

Once you find out you’re pregnant, stop using boric acid right away and switch to options with established pregnancy safety data.

It’s also a good idea to let your healthcare provider know. Share what product you used, how long you used it, and roughly when. In most cases, your provider will reassure you and recommend pregnancy safe treatments for BV or yeast infections, as outlined in the CDC’s STI Treatment Guidelines.

One non negotiable reminder: never take boric acid orally. Swallowing it can be dangerous whether you’re pregnant or not, and requires medical attention.

Bottom line: don’t panic, don’t continue using it, and loop in your provider. You didn’t know, and now you’re doing the right thing.

Dangers of boric acid suppositories

Boric acid suppositories can be helpful for some people in very specific situations, but they’re not risk free. Understanding the potential downsides matters whether you’re pregnant or not.

Oral ingestion is dangerous.

This is the most important warning. Boric acid should never be taken by mouth. Swallowing boric acid can cause nausea, vomiting, diarrhea, abdominal pain, kidney injury, seizures, and in severe cases, death. Oral exposure requires urgent medical attention. If ingestion happens accidentally, poison control or emergency care should be contacted right away.

Local side effects can happen even with correct vaginal use.

When used vaginally, some people experience burning, irritation, watery discharge, redness, or worsening discomfort. Irritation is more likely if the vaginal tissue is already inflamed or damaged. If symptoms worsen instead of improve, that’s a sign to stop and check in with a clinician.

Not FDA approved and product quality varies.

Boric acid suppositories are typically sold over the counter as supplements, not FDA approved medications. The U.S. Food and Drug Administration explains that supplements are not reviewed for safety, effectiveness, or dose consistency before being sold. That means different brands may dissolve differently, contain different amounts of boric acid, or include additional ingredients that haven’t been well studied.

They can mask the wrong diagnosis.

Yeast infections and bacterial vaginosis can feel similar, but they need different treatments. Using boric acid without testing can delay proper care, especially if symptoms are caused by something else entirely.

When to see your doctor about vaginal infections

If something feels off down there and it’s not clearing up quickly, that’s your cue to check in with a healthcare provider. Symptoms that warrant medical attention include strong or fishy odor, green or yellow discharge, thick cottage cheese like discharge that doesn’t improve, intense itching or burning, pain during sex or urination, vaginal bleeding that isn’t your period, fever, or pelvic pain. These signs can point to different conditions that need different treatments, and guessing can make things worse.

Self diagnosis is tricky, even for people who’ve had infections before. Yeast infections and bacterial vaginosis can feel similar, but they’re caused by different imbalances and require different medications.Treating without proper diagnosis can delay effective care and increase the risk of recurrence or complications, especially if the underlying issue isn’t what you think it is.

This matters even more during pregnancy. Certain infections, like BV, have been associated with pregnancy complications, which is why clinicians recommend evaluation and pregnancy safe treatment rather than trial and error. Getting the right diagnosis helps your provider choose options with established safety data and avoid products that aren’t recommended in pregnancy.

Bottom line: before starting anything new, especially supplements or OTC treatments, talk to your doctor, midwife, or nurse practitioner. A quick exam or test can save you time, discomfort, and unnecessary risk, and get you relief faster with the safest option for your body and your pregnancy.

Boric acid, pregnancy, and making informed choices

Boric acid sits in a frustrating gray area. There’s no strong evidence showing that it directly causes miscarriage, but there also isn’t enough high quality pregnancy data to consider it safe.

The good news is that avoiding boric acid doesn’t mean ignoring symptoms or suffering through them. Pregnancy safe treatments for BV and yeast infections do exist, and they’re backed by decades of clinical use and research. When safer options are available, the potential risks of boric acid simply outweigh the benefits during pregnancy.

If you used boric acid before realizing you were pregnant, don’t spiral. Brief, unintentional use is unlikely to cause harm, and this situation is far more common than people talk about. The right next step is to stop using it and let your healthcare provider know so they can document the exposure and guide you forward.

If you’re experiencing uncomfortable vaginal symptoms, whether you’re pregnant or not, talk to your healthcare provider as a first step. Since many supplements, like intravaginal boric acid, aren’t safe during pregnancy, it’s best to get their advice before starting any sort of treatment regimen.

Pregnancy is one of those seasons where caution is care, and looping in your provider is always the safest move.