title: Twins and other multiples: progress with a price.
authors.forename: L G
authors.initials: LG
authors.lastname: Keith
mesh_terms: D000367:Age Factors; D005260:Female; D006801:Humans; D007247:Infertility, Female / Q000628:therapy*; D009774:Obstetrics / Q000639:trends; D011247:Pregnancy; D011272:Pregnancy, Multiple / Q000706:statistics & numerical data*; D012307:Risk Factors