Most early miscarriages are caused by random chromosomal errors in the embryo, which means many cannot be prevented no matter what you do. More than half of losses before 12 weeks fall into this category. That said, there are real, evidence-backed steps that can lower your overall risk, and understanding which factors are within your control can make a meaningful difference.
Why Most Early Miscarriages Aren’t Preventable
About 80% of all miscarriages happen within the first 12 weeks of pregnancy. The single biggest cause is a problem with the embryo’s chromosomes: an extra copy, a missing one, or a structural rearrangement that prevents normal development. These errors happen randomly during cell division, and they become more common as egg quality declines with age. There is no supplement, medication, or lifestyle change that can fix an embryo with the wrong number of chromosomes.
This is important to understand not as discouragement, but as context. If you’ve had an early miscarriage, the odds are high that it was caused by something completely outside your control. The steps below address the other causes, the ones where your choices and your medical care genuinely matter.
Start Folic Acid Before You Conceive
The CDC recommends that all women who could become pregnant take 400 micrograms (mcg) of folic acid every day. Folic acid supports the earliest stages of embryonic development, particularly the formation of the neural tube, which happens before most people even know they’re pregnant. If you’ve previously had a pregnancy affected by a neural tube defect, the recommended dose jumps to 4,000 mcg daily, starting at least one month before conception and continuing through the first trimester.
Most prenatal vitamins contain 400 to 800 mcg of folic acid, so simply starting a prenatal before you conceive covers this base. The key is timing: by the time you get a positive pregnancy test, the critical window for folic acid’s protective effects is already underway.
Keep Caffeine Under 200 mg Per Day
The American College of Obstetricians and Gynecologists (ACOG) has reviewed the evidence and found no significant increase in miscarriage risk at caffeine levels below 200 mg per day. That’s roughly one 12-ounce cup of brewed coffee. Tea, chocolate, and some sodas also contribute to your daily total, so it’s worth checking labels if you’re a multi-source caffeine consumer. You don’t need to quit caffeine entirely, but staying under that threshold is a simple, low-cost way to reduce one known risk factor.
Reduce Exposure to PFAS Chemicals
A Yale School of Public Health study found that women with the highest levels of certain PFAS compounds in their blood had an estimated 80% to 120% increased risk of miscarriage compared to women with the lowest levels. PFAS are synthetic chemicals used in nonstick cookware, food packaging, stain-resistant fabrics, and some drinking water supplies. They don’t break down easily in the environment or in your body.
You can reduce your exposure by filtering your drinking water (carbon filters and reverse osmosis systems are most effective against PFAS), avoiding nonstick pans in favor of cast iron or stainless steel, and limiting fast food, which often comes in PFAS-treated packaging. These changes won’t eliminate exposure entirely since PFAS are so widespread, but they can meaningfully lower the amount entering your body during a vulnerable time.
Exercise Safely, Don’t Stop Moving
Regular exercise during pregnancy is not only safe, it’s recommended. ACOG advises pregnant women to get at least 150 minutes of moderate-intensity aerobic activity per week. Moderate intensity means you can hold a conversation but not sing. Brisk walking, swimming, and stationary cycling all qualify. If you were very active before pregnancy, you can generally continue the same workouts with your provider’s approval.
If you’re new to exercise, start with as little as five minutes a day and add five minutes each week until you reach 30 minutes. Avoid activities with jerky, bouncy, or high-impact movements that increase your risk of injury. Overheating is a real concern in the first trimester, so drink plenty of water, wear loose clothing, and exercise in a temperature-controlled space rather than outdoors in heat and humidity.
Progesterone for Women With Previous Losses
If you have a history of miscarriage and experience vaginal bleeding in your current pregnancy, progesterone supplementation may improve your chances of a live birth. The landmark PRISM trial, which followed over 4,000 women across 48 hospitals in the UK, found that vaginal progesterone increased live birth rates by about 5 percentage points in women with at least one prior miscarriage who were experiencing bleeding.
The benefit was dramatically larger for women with three or more previous miscarriages: 72% of those who took progesterone had a live birth compared to 57% on placebo, a 15-percentage-point difference. This is one of the most meaningful interventions available for recurrent loss, but it’s specific to a defined group of women. If you’ve had repeated miscarriages, it’s worth discussing progesterone with your provider early in a new pregnancy, ideally before bleeding starts.
Low-Dose Aspirin After Prior Loss
An NIH-funded study found that women with one or two prior miscarriages who took 81 mg of low-dose aspirin daily while trying to conceive, and continued through 36 weeks of pregnancy, improved their odds of both getting pregnant and having a live birth. The key was consistency: taking it at least four days per week. This is the same baby aspirin dose commonly available over the counter.
Low-dose aspirin is also a standard part of treatment for antiphospholipid syndrome, an immune condition that causes blood clotting problems and is one of the treatable causes of recurrent miscarriage. If you’ve had multiple losses, testing for antiphospholipid antibodies is part of the recommended workup.
Manage Thyroid and Blood Sugar
Uncontrolled diabetes raises miscarriage risk, so if you have risk factors like PCOS, obesity, or age over 40, getting your blood sugar checked before or early in pregnancy is worthwhile. A simple hemoglobin A1c test can reveal whether your blood sugar has been running high over the past few months.
Thyroid function is more nuanced than many people realize. Current guidelines from the American Society for Reproductive Medicine indicate that mildly elevated TSH levels (between 2.5 and 4 mIU/L) are not associated with increased miscarriage risk, and treatment for subclinical hypothyroidism has not been proven to reduce pregnancy loss. If your thyroid is clearly out of range, treatment matters. But you don’t need to chase a “perfect” TSH number to protect your pregnancy.
When Recurrent Loss Calls for Testing
The American Society for Reproductive Medicine defines recurrent pregnancy loss as two or more miscarriages, confirmed by a pregnancy test. If that applies to you, a structured evaluation can identify treatable causes that might otherwise go undetected. The standard workup typically includes chromosomal testing of the miscarriage tissue itself (to determine whether the loss was caused by a genetic error), evaluation of your uterine cavity for structural problems like a septum or fibroids, blood testing for antiphospholipid antibodies, and thyroid and blood sugar screening based on your risk factors.
In some cases, your provider may recommend karyotyping for both you and your partner. This checks whether either of you carries a balanced chromosomal rearrangement that could produce embryos with unbalanced genetics. If a rearrangement is found, options like preimplantation genetic testing during IVF can select embryos with normal chromosomes before transfer.
Notably, several tests that are sometimes ordered are not recommended by current guidelines. These include inherited thrombophilia panels (Factor V Leiden, MTHFR), natural killer cell testing, thyroid antibody panels, and microbiome testing. These tests have not been shown to improve outcomes, and positive results can lead to unnecessary treatments and anxiety.
What You Can Actually Control
The honest reality is that prevention of early miscarriage is limited by the fact that the most common cause, chromosomal errors, is random. But the factors within your reach are real: taking folic acid before conception, keeping caffeine moderate, staying active without overheating, reducing chemical exposures where practical, and getting tested and treated for conditions like antiphospholipid syndrome or uncontrolled blood sugar if you’ve experienced recurrent loss. For women with a history of multiple miscarriages, progesterone and low-dose aspirin have the strongest evidence behind them. Everything else is about putting your body in the best position possible and accepting that some outcomes are not a reflection of anything you did or didn’t do.