Study finds moms share phthalates with their babies.

Jan 30, 2009

Huang P, P Kuo, Y Chou, S Lin and C Lee. 2009. Association between prenatal exposure to phthalates and the health of newborns. Environment International 35:14-20.

Synopsis by Jennifer Adibi

In the first study of its kind, researchers in Taiwan find that phthalates can pass from pregnant women to their unborn babies and affect reproductive development in their daughters.

The paper reports an association between two types of the ubiquitous chemicals and permanent changes to the newborns' genitals that point to hormonal interference.  Overall, the results provide more evidence that human exposure to these endocrine-disrupting chemicals before birth can alter how reproductive systems form.

Phthalates are a class of endocrine disrupting chemicals used extensively in PVC plastics, cosmetics, food packaging and medical devices. The chemicals pollute the environment and are found in the urine of 95 percent of US residents.

In many lab studies with rodents, phthalates block the actions of two important hormones -- testosterone and estrogen -- to produce feminized male offspring and infertile females. However, few studies examine their impact on humans. The ones that do have found evidence of feminizing effects on boys exposed before birth.

Amniotic fluid and urine samples from 65 pregnant women undergoing amniocentesis were analyzed for five kinds of phthalates. At birth, the researchers measured the distance from the anus to the genitals in both male and female babies. This measure is called the anogenital distance (AGD) and indicates abnormal sexual development (specifically, differentiation) in the womb.

The metabolite monobutyl phthalate (MBP) in the amniotic fluid and urine was correlated in all newborns. This means the pollutant was able to pass from the mother, through the placenta and into the fetal circulation system.

In females only, phthalates in the amniotic fluid were correlated with shorter AGD. The association was stronger with MBP than with monoethylhexyl phthalate (MEHP). This finding is consistent with a prior study from 2005 showing a similar relationship in boys.

Even though these results support past findings, the sample size was small. Small samples make it difficult to draw statistically definite conclusions from one study alone. However, the results agree with past studies, and the findings add to the growing weight of scientific evidence that suggest prebirth exposure to some phthalates can alter reproductive development in people.

The authors conclude that "although the endocrinological and physiological influence of prenatal MBP exposure on the fetus is still a puzzle, our findings clearly showed the anti-androgenic effects of MBP on the fetus during early pregnancy."