A new study from University of Iowa Health Care, published in JAMA Psychiatry in September 2026, has been reported as linking the health of the placenta to ADHD in children. It is careful, interesting work, and it is also easy to misread. Here is what the researchers did, what they found, and why no parent should read it as a verdict on their pregnancy.
What Is PlGF?
The placenta is the organ that connects the baby to the mother's blood supply. It brings oxygen and nutrients, removes waste and acts as a partial barrier against infections and toxins. One of the proteins it makes is placental growth factor, or PlGF. PlGF helps blood vessels grow and adapt, and it passes into the mother's bloodstream, where it can be measured with a simple blood test.
Obstetricians already know PlGF well, for another reason: low levels are a warning sign of pregnancy complications, especially preeclampsia (high blood pressure in pregnancy with signs of strain on organs). In several countries, PlGF-based tests are used to help assess women with suspected preeclampsia. In short, PlGF is a window on how well the placenta is working.
What the Researchers Did
The team, led by first author Serena Gumusoglu with Alexandria Betz, Andy Storm, Donna Santillan and Mark Santillan, used a resource few hospitals have: the Perinatal Family Tissue Bank of the University of Iowa's Department of Obstetrics and Gynecology, which stores blood samples given by pregnant women who agreed to take part in research.
- They used banked maternal blood samples from 176 pregnancies, collected in all three trimesters.
- They measured PlGF in these samples, as well as a second protein involved in blood vessel function, endothelin-1.
- They then linked the pregnancies to the children's health records, to see which children later received an ADHD diagnosis and which did not.
The results were published as a research letter, a short format that reports the main finding without all the detail of a full article.
What They Found
In the pregnancies of children later diagnosed with ADHD, PlGF did not show the increase usually seen in the third trimester. According to the University of Iowa, each drop of one standard deviation in third-trimester PlGF was associated with about 2.6 times higher odds of a later ADHD diagnosis.
Three other points matter:
- There was no significant difference in the first or second trimester. The signal appeared only late in pregnancy.
- Endothelin-1 did not differ between the ADHD and non-ADHD groups.
- The link remained after the researchers took into account pregnancies with preeclampsia, fetal growth restriction or early preterm birth, three conditions already associated with both low PlGF and ADHD. As Serena Gumusoglu put it, "we aren't just flagging 'sick' pregnancies."
That last point is what makes the study interesting: subtle differences in how the placenta works, even in pregnancies without an obvious complication, might be one of the many factors that shape early brain development.
What the Study Cannot Tell Us
- It is an association, not a cause. The study shows that two things tend to go together. It does not show that low PlGF causes ADHD. The team now plans experiments in pregnant mice to test whether lowering PlGF changes brain development in the offspring.
- The sample is small. 176 pregnancies from a single medical center in Iowa is a starting point. The finding needs to be repeated in larger and more diverse groups.
- Some details are not public. The press materials do not give the number of children with ADHD, their ages, or the margin of uncertainty around the 2.6 figure. With small groups, such estimates can be imprecise.
- An odds ratio is relative. "2.6 times higher odds" compares groups. It does not mean that a child from a pregnancy with low PlGF will have ADHD, and PlGF is not a test to predict a diagnosis.
The Bigger Picture: Genes and Many Small Factors
ADHD is one of the most heritable conditions in psychiatry: twin studies estimate that genetic factors explain roughly 70 to 80 percent of the differences between people in ADHD traits. The rest comes from many small influences, several of them around pregnancy and birth, such as prematurity or low birth weight. None of them acts alone, and most children exposed to any one of them do not develop ADHD. We explain this mix in more detail in our article on what causes ADHD.
Genes and the placenta are not necessarily separate stories either. The placenta develops largely from the baby's own cells, and future studies will need to check whether part of this link is genetic. This study adds one piece to a picture that is clearly multifactorial.
No One Is to Blame
If you are the parent of a child with ADHD, it is worth saying clearly: this study does not point to anything a mother did or did not do. How the placenta works depends largely on factors no one controls, and PlGF is not something a parent can choose. Nor is ADHD a failure. It is a different way the brain develops, with real difficulties and real strengths. The value of research like this lies in understanding biology, and perhaps one day in better support during pregnancy, not in looking for someone to blame.
What This Means for You
If you are pregnant, this study does not change anything in practice: there is no recommendation to measure PlGF to predict ADHD, and your usual prenatal care remains the right place for any questions. If you are a parent wondering about your child's attention, activity or impulsivity, a structured questionnaire can help you organise what you observe before talking to a paediatrician or a specialist. Our free parent questionnaire on child ADHD takes about 10 minutes. And if, reading this, you recognise yourself more than your child, the ASRS-v1.1 adult ADHD screener (18 questions, about 10 minutes) is a good first step. Screening tests are not a diagnosis, but they can help you start the right conversation with a professional.
Source: Gumusoglu SB, Betz A, Storm A, Santillan DA, Santillan MK. "Placental Growth Factor Trajectories During Pregnancy and Child ADHD." JAMA Psychiatry, 2026 (research letter, published online September 2026). DOI 10.1001/jamapsychiatry.2026.2336. Observational study of 176 pregnancies from the University of Iowa Perinatal Family Tissue Bank; maternal blood samples from all three trimesters linked to the children's health records.