Kennislacunes

P: pregnant women without an indication for acetylsalicylic acid use, subgroups:

1. 1. singleton pregnancy without a history of preterm delivery
   2. singleton pregnancy with a history of preterm delivery
   3. multiple pregnancy without a history of preterm delivery
   4. multiple pregnancy with a history of preterm delivery

I:  low dose acetylsalicylic acid

C: placebo or no low dose acetylsalicylic acid

O: spontaneous and all preterm delivery (<28 weeks, <34 weeks, <37 weeks of gestational age)