Recurrent Pregnancy Loss: Causes, Testing, and Hope
Two or more miscarriages is devastating. Understanding why it happens — and knowing that most couples with recurrent loss do eventually have a successful pregnancy — can help you navigate what comes next.
Recurrent pregnancy loss (RPL) affects 1–3% of couples. The most common cause is chromosomal abnormality in the embryo (50–60% of cases). Even after 3 losses, the probability of a successful next pregnancy is approximately 60–75%.
When Is It “Recurrent”?
The ASRM defines recurrent pregnancy loss as two or more clinical pregnancy losses. Previously, the threshold was three, but guidelines now recommend evaluation after two consecutive losses.
Causes of Recurrent Loss
Chromosomal Abnormalities (50–60%)
The most common cause by far. Random errors during egg or sperm division produce embryos with the wrong number of chromosomes (aneuploidy). These embryos may implant but cannot develop normally. This is age-related — the risk increases significantly after 35.
Uterine Abnormalities (10–15%)
Structural issues like a septate uterus (a fibrous wall dividing the cavity), fibroids distorting the cavity, or intrauterine adhesions (Asherman syndrome) can prevent implantation or disrupt early pregnancy. Many of these are surgically correctable.
Antiphospholipid Syndrome (5–15%)
An autoimmune disorder where the body produces antibodies that increase blood clotting in the placental blood supply. Diagnosed through anticardiolipin antibodies, lupus anticoagulant, and beta-2 glycoprotein I tests. Treatable with low-dose aspirin and heparin during pregnancy.
Thyroid Dysfunction (5–10%)
Both hypothyroidism and thyroid autoimmunity (elevated TPO antibodies) are associated with increased miscarriage risk. A TSH target of 2.5 mIU/L or below is recommended for conception and early pregnancy. Treatment with levothyroxine is simple and effective.
Unexplained (25–50%)
Even after comprehensive evaluation, no cause is identified in a significant percentage of cases. The good news: unexplained RPL has the best prognosis. With supportive care alone, 60–75% of women with unexplained RPL will have a successful next pregnancy.
The RPL Workup
| Test | What It Evaluates |
|---|---|
| Karyotype (both partners) | Parental chromosomal rearrangements (balanced translocation) |
| Antiphospholipid antibodies | Autoimmune clotting risk |
| Thyroid panel + TPO antibodies | Thyroid function and autoimmunity |
| Uterine imaging (SHG or hysteroscopy) | Structural abnormalities |
| Progesterone (mid-luteal) | Luteal phase support adequacy |
PGT-A: A Prevention Strategy
Preimplantation genetic testing for aneuploidy (PGT-A) through IVF can screen embryos for chromosomal abnormalities before transfer. For couples with RPL where the primary cause is embryo aneuploidy, transferring only chromosomally normal embryos significantly reduces miscarriage rates. This is especially valuable for women over 35 where aneuploidy rates are highest.
Even after three consecutive miscarriages with no identified cause, the probability of a successful next pregnancy is approximately 60–75%. Recurrent loss is heartbreaking, but the odds are still in your favor.