When a patient tells me she is trying to conceive, the checklist she has already been given is familiar. Start folate. Stop drinking. Keep caffeine within reason. Update the vaccines. What almost never appears on that list is the class of synthetic compounds circulating in the blood of more than 98% of Americans, including hers, including mine. PFAS are not on the standard preconception handout. The evidence that they belong there has been quietly accumulating, and in the last three years it has sharpened to a point.
This is the fifth and final post in the series. If you are new to forever chemicals, Part 1 is the entry point. This installment is narrower and, for anyone planning a pregnancy, more personal. It is about what happens when two research groups, working on completely unrelated questions, arrive at the same molecule.
Two Studies, One Compound
Science earns confidence through convergence. A single association is a lead. A single mechanism is a hypothesis. When an epidemiological signal and a laboratory mechanism point independently at the same target, the picture starts to look less like coincidence and more like biology.
For PFAS and reproduction, that target has a name: perfluorodecanoic acid, or PFDA. It is not the PFAS compound most people have heard of. PFOA and PFOS get the headlines and the drinking-water limits. PFDA is a longer-chain relative that receives far less regulatory attention. It is also the compound that two separate groups, one studying human pregnancies and one studying enzyme chemistry, independently flagged as the likely worst actor.
The Epidemiology: A Fertility Signal in 382 Women
In 2023, the Mount Sinai group published an analysis of the S-PRESTO cohort, a population-based study in Singapore that enrolled women before conception and followed them forward. They measured PFAS in the plasma of 382 women who were actively trying to conceive, then tracked time to pregnancy, clinical pregnancy, and live birth over a year of follow-up.
The pattern was consistent. Each step up in exposure to individual PFAS was associated with a 5 to 10% reduction in fecundability, the per-cycle probability of conceiving. For the whole PFAS mixture, the odds of clinical pregnancy and live birth were roughly 30 to 40% lower in the higher-exposure groups. Those mixture estimates carried wide confidence intervals that brushed against the threshold of statistical significance, so they are best read as strong directional signals rather than settled conclusions. The individual-compound findings were firmer. And within the mixture, one compound contributed more than any other to the reduced odds of pregnancy: PFDA, followed by PFOS, PFOA, and PFHpA.
An epidemiologist reading this study would file it as a well-conducted human association with PFDA at the center. It cannot, on its own, establish that PFDA causes reduced fertility. That is exactly what makes the second study matter.
The Mechanism: How PFDA Could Reach the Fetus
In 2026, a group at the University of Colorado Anschutz published a mechanism paper that never set out to study fertility outcomes at all. The Colorado group was asking a chemistry question: could PFAS interfere with the enzymes that regulate retinoic acid, the vitamin A derivative that orchestrates fetal development?
Retinoic acid is one of the most tightly controlled molecules in pregnancy. It regulates over 500 genes during embryogenesis, including the ones that build the face and skull. Too little disrupts development. Too much is itself a known cause of birth defects, which is why the body holds retinoic acid within a narrow window using a family of clearance enzymes. One of those enzymes is CYP26A1. The fetus cannot make its own retinoic acid and cannot reliably clear an excess arriving from the mother, so maternal control of this pathway is what keeps fetal levels in range.
The Colorado group screened 13 prominent PFAS for their ability to inhibit that enzyme. PFDA was the most potent inhibitor of CYP26A1, and it was selective, showing no meaningful effect on the related enzyme CYP26B1. In human liver cells, PFDA went on to perturb retinoic acid metabolism and signaling directly. The authors propose that disrupting maternal retinoic acid clearance through CYP26A1 may be one pathway by which prenatal PFAS exposure contributes to craniofacial birth defects, which account for roughly a third of all congenital malformations.
This was in-vitro work, with enzyme inhibition measured at concentrations well above typical human blood levels. It does not prove harm at ambient exposures, and the authors are careful about that. It is a mechanism awaiting replication and in-vivo confirmation. But it is a mechanism that names PFDA specifically.
Why the Convergence Matters
Consider what would have to be true for this to be a coincidence. An epidemiological study in Singapore, analyzing which PFAS compounds track with reduced fertility, would have had to land on PFDA by chance. A chemistry lab in Colorado, screening which PFAS compounds disrupt a developmental enzyme, would have had to land on the same PFDA by chance.
"Two unrelated methods, two unrelated teams, two unrelated questions, one molecule."
Convergence like this does not prove causation. It does something more useful for a clinician: it moves a compound from the long anonymous list of "chemicals we detect in blood" onto a much shorter list of "chemicals with both a human signal and a plausible biological route to harm." PFDA is now on that shorter list for reproduction, and almost no one planning a pregnancy has heard its name.
What This Does, and Does Not, Mean
Honesty about limits is what makes this worth reading. The human data are associational. The mechanism is preliminary. Neither study tested whether reducing PFDA improves any outcome, and no one should read this post as a reason for alarm during an ongoing pregnancy. PFAS exposure is nearly universal and has been stable for decades, which means these are population-level risk questions, not individual verdicts. Plenty of people with detectable PFDA conceive and deliver healthy children.
What the convergence does justify is a conversation, and timing is what makes it worth having early. Lowering PFAS body burden is something a person can work on at many points in life. For reproductive risk specifically, the window that counts is before conception, because the exposures that matter are already circulating well ahead of a pregnancy, and once a pregnancy is underway, deliberately reducing body burden is off the table. Preconception is simply when the option is both safe and relevant. It is also a conversation most patients are never invited to have.
Where Plasma Enters the Picture
The uncomfortable feature of PFAS is that the body has no efficient way to clear them. They bind to proteins in plasma and persist for years. Diet, sweat, and supplements do not meaningfully move protein-bound synthetic compounds, which is the recurring theme of this entire series.
The interventions with any human evidence behind them are the ones that act on the plasma compartment directly, rather than waiting on clearance pathways that were never built for synthetic molecules. The 2022 firefighter trial is the anchor. It showed that plasma donation lowered PFAS levels, and lowered them more than whole blood donation did. That matters practically, because plasma donation is inexpensive and widely available, which makes it the most accessible starting point for anyone thinking about their body burden. Therapeutic plasma exchange works on the same compartment but moves substantially more plasma per session than donation, and a 2025 hypothesis paper has argued the case for using it serially. The honest state of that evidence is early. There is no fertility-outcome trial for either approach, and neither is something to undergo electively during pregnancy for body-burden reasons. By that point the developmental window this post is concerned with has already passed. Any discussion of reducing PFAS body burden for reproductive reasons belongs in the preconception phase, made carefully, with a physician who understands both the options and their limits. The broader case for plasma-compartment removal is laid out in the detoxification piece earlier in this series.
The Conversation Worth Having
The value of these two studies is not that they settle anything. It is that they give a name to something patients deserve to know about. When the standard preconception checklist skips the most persistent exposures in the human body, the gap is not neutral. Ask about it. Bring PFDA up by name. A physician who has never been asked may not raise it, and the evidence has now reached the point where the question is a reasonable one.
If you are thinking about reducing your environmental burden before starting a family and want to understand whether plasma exchange has any role in your situation, that is a discussion to have with a physician experienced in apheresis medicine, honestly and without overstatement.
Global Apheresis offers a Discovery Call to discuss therapeutic plasma exchange and whether it fits your situation.
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