Univariable logistic regression for preterm birth per variable before each childbirth.

a Women with induction of labor were excluded from analysis. b To adjust for multiple testing, we considered a P value of <0.001 statistically significant. c To prevent revealing data, numbers of less than 5 are grouped together, conform the rules of CBS. *Statistically significant. CBS, Statistics Netherlands; CI, confidence interval; CIN, cervical intraepithelial neoplasia; IVF: in vitro fertilization; NA, not applicable. (DOCX)