With every doubling of the concentration of the chemical in the urine of the pregnant women, their daughters underwent puberty 1.3 months earlier on an average.
Certain phthalates are used in some scented products such as perfumes, deodorants, soaps, shampoo, nail polish and cosmetics.
"We also found that girls with higher levels of parabens in their bodies at the age of nine entered puberty earlier".
Researchers from the University of California tracked nearly 200 girls from birth to adolescence, and checked for signs of puberty every nine months between the ages of nine and 13.
The chemical was measured in the mothers' urine between 14 and 27 weeks of pregnancy. For every doubling of the concentrations puberty came roughly a month earlier.
While the harsh chemicals are taking its toll on young females, the study found the elements did not impact on the development in boys.
The results, which were published December 4 in the journal Human Reproduction, came from data collected as part of the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, which followed 338 children from before birth to adolescence to document how early environmental exposures affect childhood development.
Meanwhile, there was no evidence that the said chemicals affected boys' puberty.
"There has been considerable concern about why girls are entering puberty earlier and hormone disrupting chemicals like the ones in personal care products that we studied have been suggested as one possible reason", said lead study author Kim Harley, associate director of the Center for Environmental Research and Children's Health at the University of California, Berkeley.
A limitation of the study is that girls who start puberty early are more likely to start using person care products earlier, which could be why parabens and phthalates showed in their urine.
"Earlier puberty in girls increases their risk of mental health problems and risk-taking behaviour as teenagers and increases their risk of breast and ovarian cancer over the long-term, so this is an important issue to address", she added.
Parabens are hormone-disrupting chemicals, which are used as preservatives in skincare, cosmetics and hair products.
They mimic oestrogen and may cause cancer, weight gain and reduced muscle mass.
Diethyl phthalate is harder to avoid, however, because it isn't listed on labels and is often used in fragrances, Harley said.
Triclosan, a chemical added to personal-care products to prevent bacterial contamination, has been linked to reduced heart health and an underactive thyroid. The antimicrobial agent triclosan - which the FDA banned from use in hand soap in 2017 because it was shown to be ineffective - is still used in some toothpastes.
The chemical was banned in soaps in the U.S. two years ago.
Triclosan also stops infections responding to antibiotics, which may contribute towards the resistance crisis.