A genetic variant best known for damaging the liver and lungs may also influence how long pregnancy lasts, according to a new mouse study published in Nature Communications. Researchers led by E. Koivulehto, A. Pasanen, and A.M. Haapalainen report that the AAT/SERPINA1 Pi*Z variant is associated with changes in gestational length and that treatment with alpha-1 antitrypsin, or AAT, can help prevent preterm birth in mice. The findings place a protein traditionally studied in the context of inherited lung and liver disease at the center of a potential new biological pathway affecting pregnancy.
Preterm birth, defined as delivery before 37 completed weeks of pregnancy in humans, is one of the leading causes of illness and death among newborns worldwide. Its origins are complex and can include infection, inflammation, placental dysfunction, maternal immune activation, hormonal changes, and abnormalities in the uterus or fetal membranes. Because these mechanisms frequently overlap, treatments that can safely delay early labor remain limited. The new study suggests that AAT may act not only as a circulating protective protein, but also as a regulator of inflammatory processes involved in maintaining pregnancy.
AAT is encoded by the SERPINA1 gene and belongs to a group of proteins known as serine protease inhibitors, or serpins. Its best-known function is to restrain neutrophil elastase, an enzyme released by immune cells during inflammation. Neutrophil elastase can destroy microbes, but excessive or poorly controlled activity can damage the body’s own tissues, including the lungs and the fetal-maternal interface. AAT helps maintain this balance by limiting destructive protease activity and by exerting broader anti-inflammatory effects on immune and tissue cells.
The PiZ variant changes the structure of AAT and causes the protein to misfold. Instead of being efficiently released into the bloodstream, a portion of the altered protein can accumulate inside liver cells. People who inherit disease-associated SERPINA1* variants may therefore have reduced circulating AAT and increased risk of emphysema, chronic obstructive pulmonary disease, and liver injury. The new work raises the possibility that this deficiency could have consequences during pregnancy as well, when the maternal immune system, vascular system, placenta, and reproductive tissues must undergo tightly coordinated changes.
In the mouse experiments, the researchers examined pregnancy in animals carrying the PiZ form of SERPINA1* and compared gestational outcomes with those in animals without the variant. The study links the variant to altered pregnancy duration, indicating that changes in AAT biology may influence the timing of birth. Although the genetic architecture and timing of mouse pregnancy differ substantially from those of human pregnancy, mice are valuable for testing how specific genes affect reproductive physiology and for identifying mechanisms that can be experimentally manipulated.
The researchers also investigated whether supplying AAT could counteract the effects associated with the variant. Their results indicate that AAT administration prevented preterm birth in the mouse model, a finding that gives the study its most immediate therapeutic significance. The treatment appears to support pregnancy by restoring or supplementing protective AAT activity rather than by directly suppressing labor. That distinction matters because broad suppression of inflammation can be dangerous for both mother and fetus, while targeted control of excessive protease and inflammatory signaling could offer a more selective approach.
At the biological level, the findings are consistent with a model in which insufficient or dysfunctional AAT permits inflammatory activity to rise at the wrong time. The uterus and placenta require carefully regulated immune signaling throughout gestation. Near normal labor, inflammatory mediators help promote cervical remodeling, uterine contractions, and membrane changes. If similar pathways are activated prematurely, however, they can contribute to early delivery. By limiting tissue-damaging proteases and modulating immune responses, AAT may help preserve the stability of the fetal membranes and the maternal-fetal interface until pregnancy is sufficiently advanced.
The study does not establish that the PiZ variant causes preterm birth in humans, nor does it show that AAT treatment is ready for use in pregnant patients. Human pregnancy is influenced by many genetic, environmental, and medical factors, and a variant associated with altered gestational length in mice may behave differently in people. Future research will need to determine whether pregnant individuals carrying SERPINA1* variants have measurable differences in AAT levels, inflammation, placental function, or preterm-birth risk. Clinical studies would also need to evaluate the safety, dosage, timing, and route of AAT treatment, particularly because any therapy given during pregnancy must protect two patients at once.
Even with those limitations, the work offers a potentially important shift in the search for ways to prevent premature delivery. Instead of viewing AAT solely as a protein involved in inherited pulmonary and hepatic disease, the study presents it as part of the molecular network that helps determine when pregnancy ends. If the mechanism is confirmed in humans, AAT measurements or SERPINA1 genotyping could eventually help identify selected pregnancies at increased risk, while AAT-based therapy might become one component of a more personalized strategy to delay early birth. For now, the mouse data provide a mechanistic lead: maintaining adequate AAT activity may help keep inflammation under control and pregnancy on schedule.
Subject of Research: The relationship between the AAT/SERPINA1 Pi*Z genetic variant, gestational length, preterm birth, and AAT-based prevention in mice.
Article Title: AAT/SERPINA1 PiZ variant linked to gestational length and preterm birth prevention via* AAT in mice.
Article References: Koivulehto, E., Pasanen, A., Haapalainen, A.M. et al. “AAT/SERPINA1 PiZ variant linked to gestational length and preterm birth prevention via AAT in mice.” Nature Communications* (2026). https://doi.org/10.1038/s41467-026-76643-9
Image Credits: AI Generated
DOI: 10.1038/s41467-026-76643-9
Keywords: Alpha-1 antitrypsin, AAT, SERPINA1, Pi*Z variant, preterm birth, gestational length, pregnancy, inflammation, mice, reproductive biology.
