Association between MRI-derived early second trimester placental physiology and birth weight percentiles in pregnancies without ischemic placenta disease (IPD)

This study investigated whether placental structure and function, measured using multiparametric MRI (mpMRI) in early second trimester, are associated with birth weight percentiles. We focused on pregnancies without ischemic placental disease (IPD), excluding cases with preeclampsia, fetal growth restriction (FGR), small for gestational age (SGA), or placental abruption. Clinical and pathological moderators were also examined.

In this prospective single-center cohort, 199 participants were recruited between 2017 and 2019. Placental MRI was performed at two gestational age (GA) windows: 14-16 weeks (w) and 19-24w. Placental volume, perfusion, and oxygenation were quantified and standardized to 16w for the first imaging timepoint and 20w for the second imaging timepoint. After excluding IPD cases, linear mixed-effects models were used to explore retrospective associations between MRI metrics and birth weight percentiles, adjusting for clinical and histopathological variables.

Early second trimester mpMRI showed significant associations between placental volume (positive association) and perfusion (negative association) as early as 16w GA to birthweight percentiles (p < 0.05). The nonlinear three-way interaction between the change of mpMRI parameters between 16w and 20w GA (Δ w GA) was consistently positively associated to birth weight percentiles regardless of clinical and pathological factors (p < 0.05).

Early second trimester mpMRI markers (volume and perfusion) at 16w and 20w GA are associated with birth weight outcomes, suggesting utility in early pregnancy monitoring. The three-way interaction between the mpMRI markers may serve as a composite marker for identifying variation in fetal growth trajectories.