Advancing age and the primigravida.
D000328:Adult; D001724:Birth Weight; D005260:Female; D006801:Humans; D007226:Infant Mortality; D007231:Infant, Newborn; D007234:Infant, Premature; D008423:Maternal Age; D008428:Maternal Mortality; D008875:Middle Aged; D007744:Obstetric Labor Complications; D011247:Pregnancy; D011248:Pregnancy Complications