Sunscreen chemical oxybenzone was found in every pregnant woman tested, and reached their babies

An Iranian study measured benzophenone UV filters in 166 pregnant women. BP-3 (oxybenzone) turned up in 100% of samples, and the authors report the fetus may be more exposed than the mother, though the birth-outcome links are early signals, not proof.

Teiri, H., Samaei, M. R., Dehghani, M., Azhdarpoor, A., Mohammadi, F., Kelishadi, R. & Hajizadeh, Y. (2023). Maternal exposure to benzophenone derivatives and their impacts on offspring’s birth outcomes in a Middle Eastern population. Scientific Reports, 13: 9484. https://doi.org/10.1038/s41598-023-35380-5

Benzophenones are a family of chemicals used as ultraviolet filters. The best known, benzophenone-3 (BP-3, also called oxybenzone), is a common chemical sunscreen filter. The authors describe benzophenones as endocrine-disrupting chemicals (EDCs) that may mimic and alter the function of hormones, and note they are incautiously used as UV filters in personal care products (PCPs) and plastic packaging.

Their concern is not hypothetical. Citing the international cancer agency, the authors note that these chemicals are carcinogens to animals and potential carcinogens for humans (group B), and that benzophenones can alter the hormonal balance and interrupt the evolution of the reproductive system of the fetus.

This study set out to measure how much of these chemicals pregnant women in Isfahan, Iran, were carrying, and whether those levels tracked with their newborns’ measurements. It is one of the first studies of its kind in the region, which the authors describe as one of the huge cosmetic consumer regions in the world.

Why does this matter?

The signal here is exposure during a vulnerable window. BP-3 (oxybenzone) is hormone-active, and the authors report it can cross the placenta into the developing baby. That places a precautionary spotlight on chemical UV filters during pregnancy.

This connects to a theme across our filter articles: oxybenzone and related chemical filters are absorbed through skin into the body. Mineral filters (zinc oxide, titanium dioxide) are not hormone-active in this way and sit on the skin's surface, which is one reason they are the preferred choice during pregnancy.

The essential caveat: this is a cross-sectional study of one group of women. It measures associations at a single point in time and, in the authors’ own words, cannot show cause. It does not prove that oxybenzone caused the harm.

What the researchers did

The team recruited 166 pregnant women from the PERSIAN birth cohort in Isfahan and measured four benzophenone metabolites in their urine during the first and third trimesters: 4-OH-BP (4-hydroxybenzophenone), BP-3 (2-hydroxy-4-methoxybenzophenone, also called oxybenzone), BP-1 (2,4-dihydroxybenzophenone) and BP-8 (2,2′-dihydroxy-4-methoxybenzophenone). They then recorded each newborn’s measurements at birth, including weight, length, head, arm and thoracic circumference, and anterior fontanelle diameter (the soft spot on a baby’s skull), and used statistical models to look for associations, adjusting for factors like gestational age, weight gain, smoking and income.

The paper does not treat these as harmless. It describes the derivatives as compounds with estrogenic activity and estrogen disruption properties that can accumulate in the blood, liver and kidneys through penetration from the skin, and names pregnant women and their infants as the group most at risk:

FROM THE PAPER

“The most vulnerable group to these pollutants is pregnant women and their infants.”

What they found

The exposure was near-universal. BP-1 and BP-3 were detected in 100% of samples in both trimesters, with 4-OH-BP and BP-8 close behind. BP-3, the sunscreen filter, was the dominant compound, which the authors tie directly to the consumption of sunscreen, as a health care product containing BP-3.

The more striking point is about the baby. These chemicals are small enough to cross the placenta, and the authors report that the transmission of 4-OH-BP from mother to fetus has been reported to be higher than for the other metabolites. Their conclusion about who carries the greater burden is direct:

FROM THE PAPER

“This reveals that the fetus is more likely than the mother to be exposed to these compounds, which may have harmful impacts on the health and normal development of the fetus during pregnancy.”

On birth outcomes, the study reports a scatter of associations rather than one clean effect. Higher first-trimester 4-OH-BP was linked to a smaller anterior fontanelle but a larger head and arm circumference; some effects appeared in boys but not girls, or reversed between trimesters. The authors’ overall conclusion is cautious but clear:

FROM THE PAPER

“All the target BP derivatives can influence normal fetal growth at any age of the pregnancy, nevertheless, to support these findings further studies are needed in a large and different group population.”

How firm are these findings?

Most importantly, the design cannot establish cause. On this the authors are unambiguous:

FROM THE PAPER

“Cross-sectional study cannot show causal relationships properly.”

The right way to read it is as an early signal from a heavily exposed population, not as proof that these filters damage development.

Even with those limits, the findings sit alongside a wider body of evidence that oxybenzone and related benzophenones are hormone-active and are absorbed into the body. The authors themselves call for regulatory caution:

FROM THE PAPER

“More attention is needed to regulate its use in cosmetic products and to monitor its exposure.”

For pregnant women who want to remove doubt entirely, mineral sunscreens offer a straightforward alternative. Zinc oxide and titanium dioxide provide broad-spectrum protection without the hormone activity or skin absorption that raise questions about chemical filters like oxybenzone. This is a precautionary choice, not a verdict that oxybenzone has been proven harmful in pregnancy.

Questions readers may have

Does this study show sunscreen harms babies?

It found that a sunscreen chemical, oxybenzone, was present in every pregnant woman tested and can reach the fetus, and it noted some associations with birth measurements. But it is a cross-sectional study, which the authors say cannot show cause. It is a reason for caution, not proof of harm.

What is oxybenzone and why is it a concern in pregnancy?

Oxybenzone (BP-3) is a chemical UV filter used in many sunscreens and cosmetics. It is absorbed through the skin, is hormone-active, and, as this study reports, can cross the placenta. Because pregnancy is a sensitive window for development, exposure to hormone-active chemicals during it draws particular scrutiny.

Why were levels so high in this group?

The women live in a hot, high UV region with heavy sunscreen and cosmetic use, and the authors note the country is a major cosmetics market with some low-cost products of variable quality. Detection was near-universal, so the study captures a relatively high-exposure population, which is useful for spotting signals but limits how far the results generalise.

What can I do if I want to avoid these chemicals?

Choosing a mineral (zinc oxide or titanium dioxide) sunscreen avoids benzophenone filters entirely, while still giving broad-spectrum protection. Sun protection during pregnancy remains important; the point is the type of filter, not whether to protect your skin.

About the researchers

Hakimeh Teiri

Lead author. Student Research Committee, Department of Environmental Health Engineering, School of Health, Shiraz University of Medical Sciences, Iran. Led the investigation, methodology and original drafting.

Mohammad Reza Samaei

Co-corresponding author. Department of Environmental Health Engineering, School of Health, Shiraz University of Medical Sciences. Contributed supervision and data curation.

Mansooreh Dehghani

Co-corresponding author. Department of Environmental Health Engineering, School of Health, Shiraz University of Medical Sciences. Contributed supervision and data curation.

Abooalfazl Azhdarpoor

Department of Environmental Health Engineering, School of Health, Shiraz University of Medical Sciences. Contributed conceptualisation, methodology and supervision.

Farzaneh Mohammadi

Department of Environmental Health Engineering, Faculty of Health, Isfahan University of Medical Sciences. Contributed methodology, formal analysis and validation.

Roya Kelishadi

Environment Research Center, Research Institute for Primordial Prevention of Non-Communicable Diseases, Isfahan University of Medical Sciences. A prominent paediatric and public-health researcher; contributed supervision and data curation.

Yaghoub Hajizadeh

Environment Research Center, Research Institute for Primordial Prevention of Non-Communicable Diseases, Isfahan University of Medical Sciences. Contributed conceptualisation, methodology and supervision.

Funding and competing interests: The authors declare no competing interests. The work was supported by Shiraz University of Medical Sciences (Grant No. 20258); the main cohort was funded by Iran’s Ministry of Health and Medical Education. The study was approved by the Persian Cohort Ethics Committee.

Source: Teiri, H., Samaei, M. R., Dehghani, M., Azhdarpoor, A., Mohammadi, F., Kelishadi, R. & Hajizadeh, Y. (2023). Maternal exposure to benzophenone derivatives and their impacts on offspring’s birth outcomes in a Middle Eastern population. Scientific Reports, 13: 9484. Open access, CC BY 4.0.