<p><strong>BACKGROUND: </strong>As population lead levels decrease, the toxic effects of lead may be distributed to more sensitive populations, such as infants with poor fetal growth.</p>

<p><strong>OBJECTIVES: </strong>To determine the association of prenatal lead exposure and fetal growth; and to evaluate whether infants with poor fetal growth are more susceptible to lead toxicity than those with normal fetal growth.</p>

<p><strong>METHODS: </strong>We examined the association of second trimester maternal blood lead levels (BLL) with birthweight-for-gestational age (BWGA) z-score in 944 mother-infant participants of the PROGRESS cohort. We determined the association between maternal BLL and BWGA z-score by using both linear and quantile regression. We estimated odds ratios for small-for-gestational age (SGA) infants between maternal BLL quartiles using logistic regression. Maternal age, body mass index, socioeconomic status, parity, household smoking exposure, hemoglobin levels, and infant sex were included as confounders.</p>

<p><strong>RESULTS: </strong>While linear regression showed a negative association between maternal BLL and BWGA z-score (β=-0.06 z-score units per log BLL increase; 95% CI: -0.13, 0.003; P=0.06), quantile regression revealed larger magnitudes of this association in the &lt;30th percentiles of BWGA z-score (β range [-0.08, -0.13] z-score units per log BLL increase; all P values&lt;0.05). Mothers in the highest BLL quartile had an odds ratio of 1.62 (95% CI: 0.99-2.65) for having a SGA infant compared to the lowest BLL quartile.</p>

<p><strong>CONCLUSIONS: </strong>While both linear and quantile regression showed a negative association between prenatal lead exposure and birthweight, quantile regression revealed that smaller infants may represent a more susceptible subpopulation.</p>

<p>Infants born preterm are at increased risk of multiple morbidities and mortality. Why some women deliver preterm remains poorly understood. Prior studies have shown that cervical microRNA expression and DNA methylation are associated with the length of gestation. However, no study has examined the role of long noncoding RNAs (lncRNAs) in the cervix during pregnancy. To determine whether expression of lncRNAs is associated with length of gestation at delivery, we analyzed RNA from cervical swabs obtained from 78 women during pregnancy (mean 15.5, SD 5.0, weeks of gestation) who were participating in the Spontaneous Prematurity and Epigenetics of the Cervix (SPEC) Study in Boston, MA, USA. We used a PCR-based platform and found that 9 lncRNAs were expressed in at least 50% of the participants. Of these, a doubling of the expression of TUG1, TINCR, and FALEC was associated with shorter lengths of gestation at delivery [2.8 (95% CI: 0.31, 5.2); 3.3 (0.22, 6.3); and 4.5 (7.3, 1.6) days shorter respectively]. Of the lncRNAs analyzed, none was statistically associated with preterm birth, but expression of FALEC was 2.6-fold higher in women who delivered preterm vs. term (P&nbsp;=&nbsp;0.051). These findings demonstrate that lncRNAs can be measured in cervical samples obtained during pregnancy and are associated with subsequent length of gestation at delivery. Further, this study supports future work to replicate these findings in other cohorts and perform mechanistic studies to determine the role of lncRNAs in the cervix during pregnancy.</p>