An ingredient of the shrink-wrap plastic used to package foods may also shrink babies. Or so a provocative new study suggests.

The data, although far from definitive, would seem to justify further research — and pronto — on possible fetal stunting by phthalates, a family of widely used plasticizers and solvents.

In animals, fetal exposures to certain phthalates have been linked to reproductive-tract malformations, low birth weight and early births. Since phthalates are ubiquitous in commerce and the environment, a group of researchers decided to probe whether fetal phthalate exposures might play a role in the increasing prevalence of low-birth-weight babies — wee things born weighing less than 5.5 pounds (2,500 grams).

Renshan Ge of the nonprofit Population Council in New York City (a group John D. Rockefeller III founded nearly 60 years ago), recruited 201 mothers who had just given birth in Shanghai, China. Each had her blood tested and agreed to permit assays of her newborn’s diapers. Additional umbilical cord blood was collected from each mother-newborn pair to measure phthalates that had been circulating in the infants at birth.

Moms of the low and normal-weight newborns were all about the same age, had similar educational backgrounds and household incomes, were almost exclusively nonsmokers and came from predominantly urban areas.

As Ge’s team had suspected, the 88 low-birth-weight babies indeed showed evidence of exposure to “significantly higher phthalate levels” than did the 113 normal-weight newborns. The researchers have just published their observations online, ahead of print, in the Journal of Pediatrics.

In umbilical-cord blood, they found the median concentration of DBP — or di-n-butyl phthalate — was 2.7 milligrams per liter in tiny babies; that’s a 50 percent increase over median values measured in normal-weight newborns. DBP is not only used in polyvinyl chloride plastics, but also in adhesives, insecticides and personal-care products such as nail polish, perfumes and deodorants.

A DBP breakdown product known as MBP tainted the meconium — fetal feces that are not excreted until shortly after birth — in all of the newborns’ diapers. Median MBP values in the low-birth-weight babies was 2.2 milligrams per gram, or about 30 percent higher than in meconium from normal-weight babies.

Residues of MEHP — or mono-2-ethylhexyl phthalate, a breakdown product of di-2-ethylhexyl phthalate — were more than twice as high in the mom’s and cord blood of low-birth-weight babies as in these blood sources from normal-weight infants. MEHP values were also nearly twice as high in the tiny newborns’ meconium. Consistent with this trend, residues of MEHP’s parent compound, was higher in the blood from the low-birth-weight mother-infant pairs, although only slightly so. Presumably because DEHP, the parent phthalate, broke down before much of it could be detected.

DEHP is found in some perfumes and flexible polyvinyl chloride products — such as shower curtains, diapers, the plastics used in food packaging and a host of medical equipment (from blood bags and catheters to tubing).

Higher than normal phthalate concentrations in the Shanghai newborns were also associated with the babies having shorter body lengths.

There was a time in the not too distant past when weighing less than six pounds was effectively a death sentence for newborns. Today, good hospitals can keep most of these tiny babies alive, although the youngsters face a heightened risk of dying before the age of five. And among those who do survive, low birth weight can leave a disturbing legacy, Ge’s group notes: increased adult risk of heart and metabolic disease.

So moms and wannabe’s take heed: Unless and until DEHP and DBP get a clean bill of health, it would seem prudent to employ the precautionary principle during pregnancy — i.e. forego phthalate-laden primping products, such as nail polish, perfumes and hair sprays. And if the house is being gussied up for baby’s arrival, steer clear of smelly construction sealants, grouting agents and adhesives, which also can contain notable concentrations of DBP.

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