Most miscarriages cannot be prevented. Roughly half of all first-trimester losses are caused by random chromosomal abnormalities in the embryo, events that happen by chance during cell division and are completely outside anyone’s control. That’s a hard truth, but it’s an important starting point: if you’ve experienced a miscarriage, it almost certainly wasn’t caused by something you did or failed to do.
That said, there are real, evidence-based steps that reduce the risk of pregnancy loss tied to manageable health conditions, infections, and lifestyle factors. The rest of this article focuses on those.
Why Most Early Losses Aren’t Preventable
When an embryo receives the wrong number of chromosomes during fertilization or early cell division, the pregnancy typically cannot survive. Numerical chromosome errors account for about 86% of all chromosomally abnormal first-trimester losses. These errors become more common with age. Among women who conceive between ages 35 and 44, roughly 27% of pregnancies end in loss, compared to significantly lower rates in younger age groups. This increase is driven largely by a higher rate of chromosomal mistakes in eggs as they age, not by anything a person can change through behavior.
Understanding this removes a heavy burden of guilt. For the remaining causes of miscarriage, though, there are meaningful things you can do before and during pregnancy.
Manage Blood Sugar Before Conception
If you have diabetes (type 1 or type 2), your blood sugar control in the earliest weeks of pregnancy matters enormously. High glucose levels during the first eight weeks increase the risk of both miscarriage and birth defects. The critical window is so early that many people don’t yet know they’re pregnant, which is why preconception planning is essential.
The target is an HbA1c below 48 mmol/mol (about 6.5%) before you conceive. If you can’t reach that number, getting as close as possible still helps. Every improvement in blood sugar control reduces the risk of complications. If you’re diabetic and thinking about pregnancy, working with your care team to optimize your levels ahead of time is one of the most impactful things you can do.
Get Your Thyroid Checked
An underactive thyroid, even a mildly underactive one, raises the risk of miscarriage in the first trimester. Women with thyroid-stimulating hormone (TSH) levels between 2.5 and 4.87 mIU/L have about a 47% higher risk of miscarriage compared to those with levels in the optimal range of 0.4 to 2.5 mIU/L. When TSH rises above 4.87, the risk nearly doubles.
The tricky part is that mildly elevated TSH often causes no symptoms you’d notice. A simple blood test before or early in pregnancy can catch it. If your levels are high, treatment with thyroid hormone replacement is straightforward and effective at bringing TSH into a safer range.
Progesterone for Specific Situations
Progesterone plays a critical role in maintaining the uterine lining during early pregnancy. For women who experience vaginal bleeding during pregnancy and have a history of previous miscarriage, progesterone supplementation can improve outcomes. UK clinical guidelines now recommend vaginal progesterone for women in this specific situation, continuing until 16 weeks of pregnancy.
This isn’t a blanket recommendation for all pregnant women. The benefit has been demonstrated in a specific group: those with confirmed intrauterine pregnancy, active bleeding, and at least one prior loss. If you’re in that situation, it’s worth raising with your provider early.
Cervical Insufficiency and Cerclage
Some women experience second-trimester losses caused by the cervix opening too early, painlessly and without contractions. This is called cervical insufficiency, and it’s one of the more treatable structural causes of pregnancy loss.
A cervix measuring 25 mm or shorter before 24 weeks, detected on ultrasound, can signal a problem. For women with a history of second-trimester loss or preterm birth, a cerclage (a stitch placed around the cervix to keep it closed) can effectively prolong the pregnancy. In studies, women who received cerclage carried to a median of about 38 weeks, with miscarriage rates of only 2 to 3%. If you’ve had a prior second-trimester loss, cervical length monitoring via ultrasound between 18 and 22 weeks is a standard part of care.
Food Safety During Pregnancy
Certain infections, particularly listeriosis and toxoplasmosis, can cause miscarriage. Both are contracted through contaminated food. The good news is that specific food safety habits dramatically reduce your exposure.
The core principles, per the CDC:
- Deli meats, hot dogs, and fermented sausages: Heat to 165°F (steaming hot) before eating. Listeria can grow even at refrigerator temperatures.
- Soft cheeses: Only eat those made from pasteurized milk. If you’re unsure, heat them to 165°F.
- Eggs: Cook until both yolks and whites are firm. Avoid homemade dressings or mousses made with raw eggs unless using pasteurized eggs.
- Seafood: Cook fish to 145°F. Cook shellfish until shells open and flesh is opaque. Avoid refrigerated smoked fish unless it’s in a sealed shelf-stable package or you’re cooking it into a dish.
- Produce: Wash all fruits and vegetables. Cooked sprouts are safe; raw sprouts are not recommended.
- Juice and milk: Stick to pasteurized versions. If you only have unpasteurized juice, bring it to a rolling boil for at least one minute.
- Raw dough and batter: Avoid unless made with heat-treated flour and pasteurized eggs, or specifically labeled as safe to eat raw.
For toxoplasmosis specifically, the risks extend beyond food. Wear gloves when gardening or handling soil, and if you have cats, have someone else clean the litter box during pregnancy.
Caffeine and Substance Use
The American College of Obstetricians and Gynecologists considers moderate caffeine intake, under 200 mg per day, unlikely to be a major contributor to miscarriage or preterm birth. That’s roughly one 12-ounce cup of brewed coffee. You don’t need to eliminate caffeine entirely, but staying under that threshold is a reasonable precaution.
Smoking, alcohol, and recreational drug use all increase miscarriage risk. Smoking restricts blood flow to the placenta. Alcohol has no established safe level during pregnancy. If you use any of these, stopping before or as early in pregnancy as possible offers the clearest benefit.
Workplace and Environmental Exposures
Certain chemicals found in industrial and healthcare settings are recognized reproductive hazards. Lead, ethylene oxide, and some pesticides and solvents are among the substances OSHA specifically identifies as harmful to reproductive health, capable of causing miscarriage, infertility, or birth defects.
If your job involves regular contact with chemicals, heavy metals, radiation, or anesthetic gases, review your workplace’s safety data sheets and talk with your employer about exposure limits. In many cases, reassignment to lower-risk duties during pregnancy is an option. Wearing appropriate protective equipment and following ventilation protocols makes a real difference for exposures that can’t be fully eliminated.
What Doesn’t Help
Low-dose aspirin is sometimes prescribed during pregnancy, but for miscarriage prevention, it only has evidence behind it in one narrow situation: confirmed antiphospholipid syndrome, an autoimmune clotting disorder. Despite being widely prescribed for recurrent pregnancy loss without this diagnosis, randomized trials show no improvement in live-birth rates for women without the condition. If you’ve been offered aspirin after recurrent losses, it’s worth confirming whether you’ve actually been tested for antiphospholipid antibodies.
Bed rest, avoiding exercise, and limiting normal daily activity have not been shown to prevent miscarriage. Moderate physical activity during a healthy pregnancy is safe and beneficial. The impulse to “take it easy” is understandable, but restricting movement doesn’t change outcomes and can add unnecessary anxiety.