Figure 2. Illustration of effect modification between parity and case status over time.
The likelihood of a HLA PRA class I > 10% elevating among women with spontaneous preterm delivery compared to women with normal term delivery over time differed significantly by parity in multiparous women with spontaneous preterm delivery, exhibiting the greatest risk relative to nulliparous women over time. TD, normal term delivery; sPTD, spontaneous preterm delivery; OR, odds ratio.