Potential selection bias in hospital-based studies of perinatal outcome.
D005260:Female; D006761:Hospitals / Q000706:statistics & numerical data; D006801:Humans; D007230:Infant, Low Birth Weight; D007231:Infant, Newborn; D007234:Infant, Premature; D011247:Pregnancy; D011256:Pregnancy Outcome / Q000453:epidemiology*; D015983:Selection Bias; D015030:Zimbabwe / Q000453:epidemiology