Autoimmune/Thrombophilic Disorders (as RPL Causes)

Autoimmune and thrombophilic disorders are conditions that make blood clot too easily or disturb how the immune system accepts a pregnancy. Some are acquired, and some are inherited. They can harm implantation, placentation (the growth of the placenta), and early pregnancy.

A careful workup can identify these disorders. They are among the known, treatable causes of recurrent pregnancy loss. Treatment works best when it targets the full profile that a workup finds, not one marker alone.

The group has two overlapping parts. The first part is immune conditions. These include antiphospholipid syndrome and thyroid autoimmunity.

The second part is inherited clotting disorders (thrombophilias). These include Factor V Leiden, the prothrombin G20210A mutation, and deficiency of protein C or protein S.

Inherited thrombophilias alter the function of clotting factors. This change makes clots more likely in small blood vessels, including the vessels of the placenta.¹ Not every carrier has a problem in pregnancy.

Several factors determine how serious a thrombophilia is. They include the type of mutation and other risk factors. Zygosity, whether a person carries one or two copies of the gene, also matters. Targeted testing can identify these conditions before the next attempt at pregnancy.

On the immune side, antiphospholipid syndrome is the best-studied immune cause of pregnancy loss. It has a known mechanism and a clear treatment path. The evidence on thyroid autoimmunity is less settled on both counts.

Thyroid antibodies are associated with more miscarriage, even when thyroid hormone levels are normal.² Whether treatment changes outcomes is a separate question.

The TABLET randomized trial tested that question. It enrolled women only because they had thyroid peroxidase antibodies. Their thyroid hormone levels were normal (euthyroid). Each woman received levothyroxine or a placebo. Live birth rates were no better than placebo: 37.4% versus 37.9%.³

The trial tested one drug against one marker. Any other clotting, immune, or uterine findings went untreated. A different strategy treated whatever combination of factors a workup found.

That combination could include thyroid disorders, thrombophilia, a high Th1/Th2 immune ratio, or chronic endometritis. In women under 40, the combined approach produced a 78.1% live birth rate. The untreated comparison group reached 42.3% (p=0.002).⁴

The role of natural killer cell activity at the implantation site remains under study. Identifying which condition, or which combination, is present sets the direction of care.

Anticoagulation (blood-thinning therapy), immune care, and thyroid care each work by a different mechanism. One cannot substitute for another. Treatment follows the diagnosis, not the number of losses.⁵

These conditions can be diagnosed. Women with recurrent loss who carry them do not have unexplained loss. RRM approaches recurrent pregnancy loss as a problem to diagnose, rather than a label given once everything else is ruled out.

Related entries: thrombophilia, methylated folate and MTHFR.