Look, miscarriage is rough. I've walked this road with close friends, and that helpless feeling when someone asks "what can cause a miscarriage?" sticks with you. Most times, there's no single villain to blame, but understanding the possibilities helps. Let's cut through the noise and talk real causes—not old wives' tales.
Quick reality check: 10-20% of confirmed pregnancies end in miscarriage. Before 12 weeks? That number jumps to about 80% of losses. It's more common than most folks realize.
Chromosomal Issues: The Biggest Player
Here's the deal: over half of early miscarriages happen because the embryo's chromosomes don't line up right. Think of it like a recipe with missing ingredients—sometimes things just don't combine properly at conception. This isn't about the parents' health; it's random biological luck.
| Chromosomal Problem | What Happens | Can You Prevent It? |
|---|---|---|
| Trisomy (extra chromosome) | Most common type (e.g., Down Syndrome is trisomy 21) | No—random error during cell division |
| Monosomy (missing chromosome) | Turner Syndrome is one example | No |
| Triploidy | Extra set of chromosomes (69 instead of 46) | No |
I remember my friend Jenna blaming herself for months after her loss. Her doctor finally explained: "This wasn't your fault. It's like planting a seed that never sprouts—nothing you did caused it." That talk lifted a weight off her shoulders.
Mom's Health Conditions That Raise Risks
Some health issues make your body less pregnancy-friendly. Not gonna sugarcoat it—this is where proactive care matters.
Autoimmune and Blood Disorders
Your immune system can turn against the pregnancy. Antiphospholipid syndrome (APS) is a big one—it makes your blood clot too easily, choking off blood flow to the placenta.
- APS signs: History of blood clots, recurrent miscarriages after 10 weeks
- Action plan: Blood thinners (like heparin) during pregnancy
Thyroid Troubles
Both underactive and overactive thyroids cause problems. Uncontrolled hypothyroidism? Doubles miscarriage risk. Hyperthyroidism? Also dangerous. Get those levels checked before conceiving.
Diabetes Drama
High blood sugar in early pregnancy is brutal for development. One study showed uncontrolled diabetes hikes miscarriage risk by 30-60%. Scary, but manageable—tight glucose control before conception is key.
Honestly? I've seen women panic over a single sushi meal while ignoring sky-high blood sugar. Priorities matter.
Infections That Can Trigger Miscarriage
Some germs can cross the placenta and wreck havoc. These aren't your average colds:
- Listeria: Found in unpasteurized cheese/lunch meats. Causes fever and flu-like symptoms
- Parvovirus B19 (Fifth Disease): That "slapped cheek" childhood illness. Risky before 20 weeks
- Toxoplasmosis: From cat litter or undercooked meat. Wear gloves gardening!
- STIs: Chlamydia/gonorrhea often show no symptoms but cause inflammation
Practical tip: Cook meats thoroughly, avoid soft cheeses, and get STI tested when planning pregnancy. Simple stuff lowers risks.
Hormonal Imbalances: The Silent Saboteurs
Hormones run the pregnancy show. When they're off, trouble follows:
| Hormone Issue | Effect on Pregnancy | Solution |
|---|---|---|
| Low progesterone | Can't sustain uterine lining | Supplements *may* help (controversial) |
| Thyroid imbalances | Disrupts fetal development | Medication adjustment |
| Prolactin overload | Interferes with ovulation/implantation | Medication like bromocriptine |
Structural Issues: When Anatomy Works Against You
Sometimes the uterus itself causes problems:
- Septate uterus: A wall of tissue divides the uterus (like a partial wall in a room)
- Fibroids: Non-cancerous growths that distort the uterine cavity
- Incompetent cervix: Cervix opens too early (usually after 14 weeks)
Surgery can fix some issues—like removing that septum or big fibroids. For weak cervixes, a "cerclage" stitch helps hold things closed.
Lifestyle and Environmental Factors
Time for real talk about daily choices. Some matter more than others:
Smoking and Vaping
Nicotine restricts blood flow to the placenta. Heavy smokers? 35% higher miscarriage risk. Quitting cold turkey is ideal, but even cutting back helps.
Alcohol
No safe amount exists during pregnancy. Drinking in first trimester increases miscarriage risk by 20-40%. Period.
Caffeine Confusion
Under 200mg daily (one 12oz coffee) seems okay. But guzzling espresso all day? Studies link >500mg daily to higher risks. Switch to decaf after your morning cup.
| Substance | Risk Level | When It's Most Dangerous |
|---|---|---|
| Alcohol | High | Entire first trimester |
| Nicotine | High | All pregnancy stages |
| Caffeine (>300mg/day) | Moderate | Weeks 8-14 |
Other Factors Worth Knowing
Some things you can't change, but should understand:
- Age matters: At 20, miscarriage risk is ~12%. At 40, it's 26%. Eggs age—it's biology, not judgment.
- Previous losses: One miscarriage? Same odds next time. Three or more? Doctors investigate.
- Weight extremes: Severe obesity (BMI>40) or underweight (BMI<18.5) disrupts hormones.
- Trauma: Major abdominal injury can cause loss, especially late-term.
Heads up: Advanced paternal age (>45) slightly increases risks too. Not just a "mom" thing.
Debunking Miscarriage Myths
Let's shut down harmful misinformation:
- Exercise: Moderate activity is GOOD unless your doctor restricts it
- Sex: Doesn't cause miscarriage (unless placenta previa diagnosed)
- Stress: Daily anxiety won't do it. Severe trauma (like bereavement) might
- Morning sickness: Actually linked to lower miscarriage risk
Seriously, I once saw a woman panic because she lifted groceries. Unless you're deadlifting refrigerators, relax.
Can You Prevent Miscarriage?
Some causes are unavoidable (chromosomal issues). But for controllable factors:
- Control diabetes/thyroid before conceiving
- Treat infections ASAP
- Quit smoking/vaping
- Ditch alcohol completely
- Limit caffeine to <200mg daily
- Take prenatal vitamins (folic acid is crucial!)
Your best weapon? Preconception counseling. Get checked before pregnancy.
When to Worry: Warning Signs
| Symptom | What It Might Mean | Action Needed |
|---|---|---|
| Heavy bleeding with clots | Possible miscarriage in progress | Call OB immediately |
| Severe cramping (worse than period) | Uterus contracting | Emergency room if intense |
| Sudden loss of pregnancy symptoms | Possible hormone drop | Call OB for checkup |
Your Miscarriage Questions Answered
Can stress cause a miscarriage?
Regular stress? Unlikely. Extreme trauma (like losing a child or partner)? Possibly. Your boss being annoying? No.
Do fertility treatments affect miscarriage rates?
IVF pregnancies have slightly higher loss rates initially—but usually because of underlying fertility issues, not the treatment itself.
Can food cause miscarriages?
Beyond listeria risks in unpasteurized foods? No. Spicy meals didn't cause your loss, Karen.
Is bleeding always a sign of miscarriage?
Not necessarily. 20-30% of women spot in first trimester and go on to deliver healthy babies. But always get it checked.
How soon after miscarriage can I try again?
Physically? After one normal period. Emotionally? Whenever you're ready. Grief has no schedule.
Can progesterone supplements prevent miscarriage?
Only if tests show you're deficient. Routinely prescribing it? Studies show minimal benefit. Don't push for it without proof.
Does morning sickness mean lower miscarriage risk?
Generally yes—it suggests healthy hormone levels. But lack of nausea doesn't doom your pregnancy either.
Can a miscarriage be stopped?
If it's already starting? Almost never. Cervical dilation or heavy bleeding means it's inevitable.
Do abortions increase miscarriage risk later?
Safe, legal procedures don't affect future pregnancies. Back-alley abortions? Different story.
Final thought: Miscarriage sucks. But knowing what can cause a miscarriage—and what doesn't—helps you focus on real risks. Be kind to yourself. And please, ditch the guilt. Most losses are nature's heartbreaking reboot, not your fault.