Exposure to Ambient Particulate Matter during Specific Gestational Periods Produces Adverse Obstetric Consequences in Mice

BACKGROUND: ) during pregnancy with preterm birth (PTB) and low birth weight (LBW) but disagree over which time frames are most sensitive, or if effects are cumulative. OBJECTIVES: during discrete periods of pregnancy results in PTB and LBW. METHODS: (CAPs) or filtered air (FA) throughout pregnancy [6 h/d from gestational day (GD) 0.5 through GD16.5]. A follow-up study examined the effects of CAPs exposure during discrete gestational periods (1: GD0.5–5.5; 2: GD6.5–14.5; 3: GD14.5–16.5; 4: GD0.5–16.5) aligning to milestones during human development. RESULTS: for periods 1–4, respectively). Pregnancy was significantly shortened (vs. FA) by ∼0.4d when exposure occurred during gestational periods 2 and 4, and by ∼0.5d if exposure occurred during period 3. Exposure during periods 1, 2, and 4 reduced birth weight by ∼10% compared with FA, and placental weight was reduced (∼8%) on GD17.5 if exposure occurred only during period 3. The results of these experimental studies could contribute significantly to air pollution policy decisions in the future. https://doi.org/10.1289/EHP1029.