Secretory IgA (sIgA) + Hidden Infertility Clues

If you’re working on fertility or if you’re someone who has experienced recurrent pregnancy loss, there’s one stool test marker I watch really closely: secretory IgA (sIgA). It’s a simple lab value but it tells a powerful story about your immune system, and that story often links directly to implantation problems, miscarriage risk, and mysterious “why can't we stay pregnant?” cases. 

Remember, roughly 75% of your body’s immune system lives in the GUT.  If stool sIgA is low, we suspect mucosal defense could be low everywhere; gut, vagina, uterus. This means increased susceptibility to dysbiosis (Candida, BV-associated microbes), infections, and an inflammatory environment that can impair implantation.

Why sIgA matters 

sIgA is the antibody that lives on the surfaces of your body, in the gut, vagina, sinuses and more, and acts like the border patrol at those doors. It works by binding to microbes, toxins, and allergens before they can enter the body. When sIgA is healthy it:

• Neutralizes pathogens and toxins before they cross the mucosa

• Helps maintain a balanced vaginal and uterine microbiome (critical for implantation)

• Teaches the immune system to tolerate the embryo instead of attacking it (there is an estimation that 40% of unknown infertility cases are related to the immune system)

When sIgA is low the border patrol is understaffed. Pathogens and opportunistic microbes can persist, inflammation increases, toxins and hormones are more likely to get reabsorbed, and the uterine environment becomes less hospitable to an embryo.

How low sIgA shows up in fertility problems

Low sIgA doesn’t directly “cause” miscarriage, but it creates a chain reaction that does make implantation and early pregnancy fragile:

• Weakened mucosal defense → persistent vaginal/uterine dysbiosis (low protective lactobacillus, more anaerobes)

• Chronic local inflammation → impaired implantation and higher miscarriage risk

• Gut inflammation and dysbiosis → impaired nutrient absorption, poor methylation, higher oxidative stress (all reduce egg + endometrial quality)

• Increased re-circulation of estrogens and toxins → supports hyperplasia or estrogen-driven endometrial problems

Put simply: low sIgA is a red flag that says “look here” and when we act on it, outcomes often improve.

What a stool test actually allows us to do

A stool test that includes sIgA (like the GI map or Gut Zoomer that we run in my practice) will:

• Show whether low sIgA is paired with dysbiosis, Candida, H. pylori, or inflammatory markers (calprotectin, MMP-9)

• Identify whether the problem is mostly gut-driven, vaginal-driven, or systemic

• Let us target treatment in the right order (support mucosal immunity → fix digestion and liver clearance → rebalance microbes → address local uterine/vaginal issues)

  
  

Typical next steps when sIgA is low

The sequence matters. Typical priorities I follow:

• Calm and support mucosal immunity 

• Repair the gut lining

• Support liver and estrogen clearance 

• Gently rebalance the microbiome

• Test the uterine and vaginal microbiome before embryo transfer or trying again

  
  

Real benefit for fertility clients

Clients who addressed a low-sIgA + dysbiosis pattern regained regular cycles, cleared chronic yeast/UTI issues, and experienced improved implantation rates after the uterine environment was optimized. The difference wasn’t one single pill, it was a targeted sequence informed by a stool test.

If you’ve had unexplained pregnancy losses, implantation failure, recurrent vaginal infections, or gut symptoms, a stool test that includes sIgA can be the missing piece to tie your story together.