Why Do I Keep Having Miscarriages At 6 Weeks? Root Causes

Losing a pregnancy at six weeks is heartbreaking, and it is also surprisingly common. Research shows that up to 25% of recognized pregnancies end in miscarriage, with the vast majority happening in the first 12 weeks, and the 6-week mark is a particularly vulnerable time. The most common root cause is a chromosomal abnormality in the embryo that happened by chance, not because of anything you did or did not do.

What Actually Causes a Miscarriage at 6 Weeks?

The single most common cause of miscarriage at 6 weeks — accounting for 50-60% of all first-trimester losses — is a random chromosomal error in the embryo. This is not inherited. It happens during cell division after the egg is fertilized. The embryo has too many or too few chromosomes, and it cannot develop normally. The body naturally stops the pregnancy.

Other causes exist, but they are less common. Structural issues with the uterus, like a septum or fibroids, can interfere with implantation. Hormonal problems, such as low progesterone or untreated thyroid disease, may also play a role. Immune system disorders and blood clotting conditions are real but rarer causes.

It is important to know that for about 50-75% of women who have one miscarriage, no cause is ever found. That does not mean something is wrong. It means the cause was likely a one-time chromosomal error.

Why Does This Keep Happening to Me?

Having two or more miscarriages is called recurrent pregnancy loss (RPL). The American College of Obstetricians and Gynecologists defines RPL as two or more failed pregnancies. About 1-2% of women experience recurrent miscarriage, and the emotional toll is heavy.

When miscarriages repeat at the same early stage — around 6 weeks — the cause is often the same each time. Random chromosomal errors can happen more than once by bad luck. But if you have had three or more losses, doctors will look deeper for underlying issues.

Age is a major factor. By age 35, about 20% of pregnancies end in miscarriage. By age 40, that number rises to 40%. By age 45, it is 80%. The reason is that eggs age with you, and older eggs are more likely to have chromosomal errors. This is biology, not a reflection of your health or choices.

Some studies suggest that about 60-70% of recurrent miscarriages remain unexplained even after full testing. That statistic is frustrating, but it also means most recurrent losses are not caused by a treatable condition.

What Testing Should I Ask For?

If you have had two or more miscarriages, your doctor should offer a standard workup. This typically includes a blood test to check your thyroid function, blood clotting factors, and hormone levels. You should also have a karyotype test to check your and your partner’s chromosomes for balanced translocations — a structural rearrangement that can cause repeated losses.

Imaging of the uterus is also standard. A saline infusion sonogram or hysteroscopy can find polyps, fibroids, or a septum. These structural problems are correctable with surgery in many cases, and fixing them can improve pregnancy outcomes.

One test that is often overlooked but worth asking about is testing the tissue from a past miscarriage. This is called chromosomal analysis of the products of conception. It can tell you if the miscarriage was caused by a random chromosomal error. If it was, that is reassuring — it means the cause was not a problem with your body.

Research published in the journal Fertility and Sterility found that testing miscarriage tissue can reduce unnecessary treatment. If the tissue shows a chromosomal error, you can avoid invasive testing for conditions that are not relevant to your situation.

What Treatments Actually Have Evidence Behind Them?

For unexplained recurrent miscarriage, there is no proven treatment that guarantees a live birth. Many treatments are promoted online, but the evidence is weak or conflicting.

Progesterone supplementation is one of the most common treatments. Some studies suggest it may reduce miscarriage risk in women with bleeding in early pregnancy. But a large 2019 trial published in the New England Journal of Medicine found that progesterone did not improve live birth rates in women with recurrent miscarriage. The evidence is mixed.

Aspirin and heparin are used for women with antiphospholipid syndrome, a blood clotting disorder. For that specific condition, the evidence is strong. But for women without a diagnosed clotting disorder, these medications have not been shown to prevent miscarriage.

Thyroid medication is effective if you have an underactive thyroid. The American Thyroid Association recommends keeping TSH below 2.5 mIU/L before pregnancy. If your thyroid is normal, thyroid medication will not help.

Here is a simple comparison of common treatments and their evidence level:

What About Lifestyle Factors?

Lifestyle changes are often recommended, but the evidence for most of them is weak. Smoking is the one clear risk factor. Research shows that smoking increases miscarriage risk by about 25%. If you smoke, stopping is the single most impactful change you can make.

Alcohol consumption is also linked to miscarriage, though the exact threshold is unclear. The CDC advises avoiding alcohol completely during pregnancy. Caffeine intake above 200 mg per day — about one 12-ounce cup of coffee — has been associated with a slightly higher risk in some studies, but the evidence is not definitive.

Weight matters. Obesity, defined as a BMI over 30, is linked to a higher risk of miscarriage. The exact mechanism is not fully understood, but it may involve hormonal imbalances or egg quality. Losing weight before pregnancy is reasonable, but crash diets can also disrupt ovulation.

Stress is often blamed, but the evidence is weak. A 2017 review in the journal Human Reproduction Update found no clear link between stress and miscarriage. Stress is real and painful, but it is not a proven cause of pregnancy loss.

Why Do I Keep Having Miscarriages At 6 Weeks — Common Misconceptions

One of the most persistent myths is that exercise causes miscarriage. This is false. Moderate exercise during early pregnancy is safe and does not increase miscarriage risk. The American College of Obstetricians and Gynecologists confirms this.

Another myth is that sex causes miscarriage. This is also false. Sex does not cause miscarriage at any stage of pregnancy. The cervix is closed and protected by a mucus plug.

A third myth is that taking birth control pills before pregnancy causes miscarriage. This is not true. Research shows no link between past oral contraceptive use and miscarriage.

Some people believe that having a miscarriage means your body is “rejecting” the pregnancy. This is not accurate. The body is not rejecting a healthy embryo. It is ending a pregnancy that could not survive due to a genetic error.

The most dangerous myth is that you can prevent a miscarriage by resting in bed. Bed rest has been studied extensively and does not prevent miscarriage. The American College of Obstetricians and Gynecologists recommends against it. Bed rest can actually cause harm, including blood clots and muscle loss.

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