August 19, 2026, 10:58 am | Read time: 6 minutes
Phthalates are a group of chemicals found in plastics, food packaging, and personal care products. They are classified as endocrine disruptors–substances that can affect the hormonal system. Their health impacts have been studied for some time. A recent study now focuses on pregnant women.
How Do Phthalates Affect Pregnancy?
As the Federal Environment Agency also informs, phthalates can have “various effects on the organism.”1 They are substances that alter the hormonal system: endocrine disruptors. Some phthalates are also classified as reproductive hazards. Research has linked repeated exposure to certain phthalates in men with impaired fertility; FITBOOK has previously reported on this. Changes or malformations of male reproductive organs have also been studied in connection with phthalate exposure.
The authors of the current study aimed to determine the effects of phthalate exposure during pregnancy.2 During this life phase, blood pressure naturally changes. The researchers specifically examined the impact of phthalate exposure on systolic blood pressure–the upper value. FITBOOK explains how this relates to the lower, diastolic value here.
The researchers also looked at hypertensive pregnancy disorders (HDP), including gestational hypertension, preeclampsia, and preeclampsia with pre-existing high blood pressure.
Study Details
Women in the early stages of pregnancy were enrolled in the study and followed over several time points. The participants were from the Environmental Reproductive and Glucose Outcomes Study (ERGO) in Boston.3 Additionally, data from participants in the SPRING study were included.4 In total, the researchers were able to evaluate information from 338 women.
The researchers collected urine samples and blood pressure readings from the participants at three points during pregnancy–on average in the 11th, 19th, and 26th weeks. In the urine samples, they looked for 16 phthalate metabolites and two metabolites of the modern alternative plasticizer DINCH. Based on the measured concentrations of these substances, the researchers determined the level of exposure for each woman.
They also examined the blood pressure readings of the pregnant women, which were sourced from their medical records. Additionally, the researchers recorded whether a hypertensive pregnancy disorder occurred. This was the case for 43 of the 338 women studied, or about 12.7 percent.
For statistical analysis, the authors used linear regression models and models for relative risks. To further assess how the various chemicals interacted, they employed Bayesian Kernel Machine Regression. This method allows for the examination of the effects of multiple co-occurring substances together.
Results
The higher the MEP concentration in the urine, the higher the participants’ blood pressure readings. MEP is a metabolite of diethyl phthalate (DEP), used in personal care and cosmetic products. The researchers also found higher blood pressure readings for the combined group of substances ΣPCP when the concentrations of the corresponding metabolites in the urine were higher. This group includes several metabolites of chemicals found in personal care products.
This pattern was most evident during the third examination in the 26th week of pregnancy. Women with higher concentrations of MEP and ΣPCP in their urine also had higher blood pressure readings at this time.
Higher Phthalate Exposure, Higher Blood Pressure?
Significant differences were observed in systolic blood pressure. Women with the highest MEP concentrations in their urine had about 4.6 mmHg higher blood pressure in the 26th week of pregnancy than those with the lowest concentrations. For the ΣPCP group, the difference was similarly pronounced at about 5.8 mmHg.
Diastolic blood pressure was also elevated with higher MEP and ΣPCP exposure. For MEP, the difference between women with the highest and lowest exposure was about 4.5 mmHg. Overall, the differences for ΣPCP were of a similar magnitude depending on the analysis.
The results were not consistent for all substances and at all times. For some other phthalate metabolites, the researchers found abnormalities only at certain times. When considering the entire mixture of chemicals studied, a higher diastolic blood pressure was particularly evident in late pregnancy. MEP contributed most significantly to this result.
Interestingly, a modern substitute developed as an alternative to phthalates also came under scrutiny: Moderate amounts of the plasticizer DINCH were associated with a threefold increased risk of severe pregnancy disorders like preeclampsia in the study.
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Possible Significance of the Results
The study suggests that phthalate exposure during pregnancy could be linked to changes in blood pressure. However, the researchers do not issue a specific warning against certain personal care or cosmetic products during pregnancy based on their findings. FITBOOK has contacted the corresponding authors for more detailed information, but a response is still pending.
Particularly interesting on paper is that the strongest effects were observed in later pregnancy. However, the data does not allow for a conclusion on whether the chemicals studied actually influence blood pressure. Further studies would be needed to investigate a possible causal relationship more closely.
Regarding hypertensive pregnancy disorders, the results should be interpreted with caution. The indications were much less clear than for the regularly measured blood pressure values. Overall, the study primarily indicates a possible connection–it does not provide evidence that phthalates increase blood pressure or the risk of pregnancy disorders.
Limitations
The study’s significance is limited by several factors.
First, the sample size of 338 participants was relatively small. There was also a lack of diversity–the participants were of a higher educational level than the average U.S. population, as the authors acknowledge. Additionally, the prevalence of hypertensive pregnancy disorders was higher than in the general U.S. pregnancy population.
Another limitation is the urine samples. Only a single sample was taken per examination point. Since phthalates and their substitutes are excreted relatively quickly, such a snapshot may not reflect the total exposure over a longer period. For 116 participants, or 34 percent, blood pressure was measured about three to four days after the urine sample. Different measurement methods at the participating clinics could also have led to some variability.
It should also be noted that several initially statistically significant results were no longer considered significant after correction for multiple comparisons. Moreover, many results did not show a clear dose-response relationship–higher concentrations of the substances did not automatically correspond to higher blood pressure values.
This underscores that the study should be seen more as a warning signal and a guide for further research, not as definitive proof. The authors emphasize that further studies are needed to confirm and better understand the results.