PROTECT Study links common chemicals to preterm births in Puerto Rico

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PROTECT researchers have identified an association between exposure to chemicals found in many common consumer products and a shorter duration of pregnancy, thus increasing the risk of preterm birth. More specifically, the scientists found that higher urinary concentrations of phthalate metabolites in pregnant women within the first 36 weeks of pregnancy translated into a 42% greater chance of giving birth preterm compared with other women with lower exposure rates. Preterm birth is a global concern primarily occurring in resource-poor regions[1], and Puerto Rico not only has one of the highest rates in the United States but is among the highest in the world at 11.5% in 2017, according to the March of Dimes.

The main chemicals analyzed in this study, phthalates, are often found in personal care products, food, some medications, and many other commercial and consumer products. For this study, researchers took urine samples from nearly 1,100 Puerto Rican women in the PROTECT cohort at three points in time during their pregnancies, measuring for nearly a dozen markers of various phthalate chemicals. They found that higher levels of urinary metabolites later in pregnancy had a greater impact on preterm birth rates, suggesting these metabolites may produce an inflammatory and oxidative stress response that triggers birth preterm.

“In the ongoing PROTECT cohort study, we and our team of collaborators are continuing to cast a broad net to study as many factors as we can and how they may be contributing to this serious public health challenge. Since the risk of preterm birth likely involves a diverse set of influences, we continue to expand the size of our cohort study, employ a team science approach, as well as develop and utilize new methods to maximize our ability to understand this issue,” says Project 1 Leader John D. Meeker, coauthor of this recent study publication and lead in the study of toxic chemicals at PROTECT.

These findings are significant because they can potentially have broad public health implications. Because phthalates are so commonly found in personal care products, changes in product formulations, government policies around personal care products, and consumer purchasing patterns could help to reduce exposure, which may in turn help reduce the risk of preterm birth.

Fig. 1
Fig. 1. Adjusteda odds ratios (95% confidence intervals) between an interquartile range difference in urinary phthalate or phthalate alternative metabolite concentrations by study visit and preterm birth.
aAdjusted for maternal age (continuous), education (4 level ordinal variable), urinary specific gravity, and gestational age at sample collection.

Table 1. Population demographic and pregnancy characteristics among women from the PROTECT cohort (n = 1090).

Maternal age at enrollment (years) n (%)
 18–24388 (35.6)
 25–29346 (31.8)
 30–34223 (20.5)
 >35132 (12.1)
Years of education
 <High school69 (6.44)
 High school/equivalent126 (11.8)
 Some college/technical school380 (35.5)
 ≥College degree497 (46.4)
Annual household income (US dollars)
 <20,000418 (44.2)
 20,000–40,000302 (31.9)
 >40,000226 (23.9)
Marital status
 Single195 (18.1)
 Married/cohabitating881 (81.9)
Pre-pregnancy body mass index (kg/m2)
 <18.570 (6.81)
 18.5–24.9500 (48.6)
 25.0–29.9278 (27.0)
 >30180 (17.5)
 Employed699 (65.2)
 Unemployed373 (34.8)
Smoking status
Never917 (85.3)
 Ever141 (13.1)
 Current17 (1.58)
Alcohol use during pregnancy
 None1004 (93.7)
 Any68 (6.34)
Newborn sex
 Female512 (47.2)
 Male572 (52.8)
Preterm delivery (<37 weeks gestation)
 Yes101 (9.27)
 No989 (90.7)

To review the study, check out the associated publication: Environmental phthalate exposure and preterm birth in the PROTECT birth cohort

Adapted from an article published by UM.