What makes a woman more likely to miscarry

Miscarriage—losing a pregnancy before the 20-week mark—happens more often than people think, but it's still really misunderstood. Yeah, lots of miscarriages are just random chromosomal flukes in the embryo. But there are also specific things that can really crank up the risk for some women. Getting your head around these can help you stay aware and maybe even be proactive about your health.

What are the top medical conditions that increase miscarriage risk?

Some health issues you already have—or that pop up during pregnancy—are pretty strongly tied to a higher chance of miscarriage. They mess with your uterine environment, your hormones, or how well your body can actually support a pregnancy.

• Advanced Maternal Age: Age is a big deal here. The risk shoots up as you get older. A woman in her 20s has about a 10-15% chance. That jumps to 20-35% for women in their 30s, and over 40? It can hit more than 50%. Mostly because eggs are more likely to have chromosome issues.
• Uncontrolled Chronic Conditions: If diabetes, thyroid problems (both overactive and underactive), or high blood pressure aren't managed well, they can make your body a pretty tough place for an embryo to grow. Autoimmune stuff like lupus or antiphospholipid syndrome (APS) can trick your body into attacking the pregnancy itself.
• Uterine or Cervical Abnormalities: Structural problems matter. Things like fibroids (especially the kind that bulge into the uterine cavity), polyps, scar tissue (that's Asherman's syndrome), or a uterus that's divided by a wall of tissue (septate uterus) can mess with implantation or blood flow. And a "weak cervix" (cervical insufficiency) can lead to a late second-trimester loss.
• Infections: Some infections can cross the placenta and harm the baby. We're talking listeriosis (from bad food), rubella, cytomegalovirus (CMV), and really bad bacterial vaginosis.

How do lifestyle factors and habits influence miscarriage risk?

What you do day-to-day and what you're exposed to can have a huge impact on whether a pregnancy sticks. Changing these things is probably your best bet for lowering risk.

Can emotional stress or physical trauma cause a miscarriage?

People worry about this a lot. Look, extreme, long-term psychological stress might mess with your hormones enough to theoretically affect a pregnancy, but the evidence isn't strong enough to say it's a direct cause. Normal daily stress or one bad day (like a job interview or a fight) doesn't cause a miscarriage.

Same goes for moderate exercise, sex, or a minor fall—typically, they don't cause miscarriage. But serious physical trauma? Like a car wreck or a direct hit to the belly—that can be a risk factor for placental abruption and losing the pregnancy. It's important to know the difference between everyday stuff and major trauma.

"The vast majority of early miscarriages are due to random chromosomal errors, not something the mother did or didn't do. This understanding is crucial for reducing guilt and shame." — Dr. Sarah Jenkins, OB/GYN

What is the role of previous miscarriages and genetic factors?

Your pregnancy history and your genetics play a big part. Recurrent pregnancy loss (RPL) means having two or more miscarriages in a row.

• Previous Miscarriages: Your risk goes up with each loss. After one miscarriage, your risk for the next pregnancy is about 20%. After two, it's around 28%. After three or more? It can be 40-50%.
• Genetic Abnormalities: In about 50-60% of first-trimester miscarriages, the embryo has the wrong number of chromosomes (that's aneuploidy), like trisomy 16, 21, or 22. These are usually random mistakes in cell division. But sometimes, one partner carries a "balanced translocation" of chromosomes—it doesn't affect them, but it can cause unbalanced chromosomes in the embryo, leading to repeated miscarriages.
• Paternal Factors: Not as well studied, but if the father is older (over 40) or has certain sperm DNA fragmentation issues, it might also slightly raise the risk.

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