The four quarters of pregnancy.
D000028:Abortion, Induced; D001724:Birth Weight; D005260:Female; D005313:Fetal Death; D005865:Gestational Age; D006801:Humans; D007226:Infant Mortality; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular; D013997:Time Factors; D014944:World Health Organization