Multiple-pregnancy complications.
D001724:Birth Weight; D036861:Delivery, Obstetric; D005260:Female; D005865:Gestational Age; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D011044:Poland; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology*; D011272:Pregnancy, Multiple; D014310:Triplets; D014427:Twins