Preventing recurrent miscarriage starts with identifying the cause, which is possible in roughly half of cases. The other half remain unexplained, but even then, nearly two-thirds of people with recurrent pregnancy loss eventually have a healthy pregnancy, often without any extra treatment. Recurrent pregnancy loss is clinically defined as two or more failed pregnancies confirmed by ultrasound or tissue examination, and that threshold is when a full workup becomes appropriate.
What you can do depends entirely on what’s driving the losses. The major treatable categories are hormonal, anatomical, immunological, genetic, and lifestyle-related. Here’s what the evidence supports for each.
Progesterone for Early Pregnancy Support
Low progesterone can make it harder for the uterine lining to sustain a pregnancy in the earliest weeks. The largest trial on this, known as the PRISM trial, tested vaginal progesterone pessaries in women who had early pregnancy bleeding and a history of loss. Participants used 400 mg of micronized progesterone vaginally twice daily (morning and evening), starting as soon as an intrauterine pregnancy sac was confirmed on ultrasound and continuing through 16 weeks of gestation.
The benefit was most pronounced in women with three or more prior losses. For women with just one previous miscarriage, the effect was smaller. Progesterone is not a universal fix, but if your doctor suspects luteal phase insufficiency or you have a history of bleeding in early pregnancy, this is one of the best-studied interventions available. The treatment is simple, self-administered, and carries minimal side effects.
Treating Blood Clotting Disorders
Antiphospholipid syndrome is one of the most important treatable causes of recurrent loss. It’s an autoimmune condition where the body produces antibodies that increase blood clot formation in the placenta, cutting off the blood supply to the developing pregnancy. Diagnosis requires specific blood antibody tests done on two occasions at least 12 weeks apart.
The standard treatment combines low-dose aspirin (around 100 mg daily, taken orally) with a daily injection of heparin, a blood thinner. This combination significantly improves live birth rates in women with confirmed antiphospholipid syndrome. Treatment typically begins before or at conception and continues through the pregnancy. Without treatment, this condition carries a high risk of repeated loss, so testing for it is a priority during any recurrent miscarriage workup.
Checking and Managing Thyroid Function
Even mildly abnormal thyroid function can increase miscarriage risk, particularly when thyroid antibodies are present. You don’t need to have full-blown thyroid disease for this to matter. Women with thyroid antibodies face higher miscarriage rates when their TSH (the hormone that reflects thyroid activity) rises above 2.5 mIU/L.
The clinical target for women trying to prevent recurrent loss is a TSH below 2.5 mIU/L, with some evidence suggesting that below 1.5 mIU/L is even better in the earliest weeks of pregnancy. This is a tighter range than what’s considered “normal” for the general population, so a standard thyroid panel might come back as normal while still leaving room for improvement. If you’ve had recurrent losses and haven’t had both your TSH and thyroid antibodies checked, it’s worth requesting.
Correcting Uterine Abnormalities
Structural problems inside the uterus, particularly a uterine septum (a wall of tissue that partially divides the uterine cavity), are a well-established cause of recurrent loss. The septum creates a poor environment for implantation and placental growth. Submucosal fibroids, which bulge into the uterine cavity, can cause similar problems.
Surgical correction of a uterine septum produces striking results. A 20-year retrospective study found that early miscarriage rates dropped from 35.6% to 14.8% after hysteroscopic septum resection, and recurrent miscarriage specifically fell from 10.9% to just 2.0%. The procedure is minimally invasive, performed through the cervix without external incisions, and recovery is typically quick. If you haven’t had imaging of your uterine cavity (a saline ultrasound or hysteroscopy), this is a straightforward step in the evaluation process.
Genetic Factors in Both Partners
Chromosomal abnormalities in the embryo are the single most common reason any individual pregnancy fails, and they become more frequent with age. In some couples, one partner carries a balanced chromosomal rearrangement that doesn’t affect their own health but increases the chance of producing embryos with the wrong number of chromosomes.
A karyotype (chromosome analysis) of both partners is a standard part of recurrent loss evaluation. If a translocation or other rearrangement is found, IVF with preimplantation genetic testing allows embryos to be screened before transfer. For couples without a known chromosomal issue, the role of genetic testing on embryos is less clear-cut, and natural conception with close monitoring remains a reasonable path.
Sperm Quality and DNA Damage
Recurrent miscarriage isn’t exclusively a female health issue. Sperm DNA fragmentation, where the genetic material inside sperm is damaged, correlates with higher miscarriage rates. A DNA fragmentation index (DFI) below 15% is considered normal. Between 15% and 30% is average but associated with increased miscarriage risk. Above 30%, sperm DNA integrity is considered poor, and miscarriage rates rise significantly. Each 1% increase in DFI is associated with roughly a 9.5% increase in the odds of miscarriage.
Sperm DNA fragmentation testing isn’t part of a standard semen analysis, so it needs to be specifically requested. If fragmentation is elevated, potential contributing factors include smoking, heat exposure, oxidative stress, varicocele, and long intervals between ejaculations. Lifestyle changes and, in some cases, surgical correction of varicocele can improve fragmentation levels. When fragmentation remains high, techniques like ICSI (where a single sperm is selected and injected directly into the egg) may help, though the relationship between high DFI and outcomes with assisted reproduction is still being refined.
Weight, Caffeine, and Alcohol
Body weight is one of the most impactful modifiable risk factors. Women with a BMI over 25 have about 35% higher odds of further miscarriage if they already have a history of recurrent loss. A BMI over 30 raises those odds to 77% higher. Being underweight also increases risk, though to a lesser degree. Reaching a BMI between 19 and 25 before conceiving again is one of the most concrete things you can do.
Caffeine intake above 300 mg per day (roughly two to three standard cups of coffee) is linked to increased miscarriage and stillbirth risk. Some data suggests that even more moderate intake, above about 100 mg per day, may matter in the context of recurrent loss specifically. Switching to one small cup of coffee or opting for lower-caffeine alternatives is a reasonable precaution.
For alcohol, the evidence points toward abstaining entirely while trying to conceive and throughout pregnancy. Studies have shown increased miscarriage risk with as few as two to four drinks per week, and there’s no established “safe” level during pregnancy.
The Unexplained Cases
Up to 50% of recurrent pregnancy loss cases have no clearly identified cause after a full workup. That’s frustrating, but the prognosis is actually better than it sounds. Unexplained recurrent loss carries the highest natural success rate of any category, with the majority of these couples going on to have a live birth in a subsequent pregnancy without targeted treatment.
Supportive care during the next pregnancy, sometimes called “tender loving care” in the clinical literature, has measurable benefits for this group. This includes frequent early ultrasounds, easy access to a clinical team, and psychological support. The reassurance of close monitoring appears to reduce stress hormones that may themselves contribute to poor outcomes. If you fall into the unexplained category, continuing to try to conceive is a medically supported option, not just wishful thinking.