Multiple pregnancies and photoperiodicity.
D000328:Adult; D005260:Female; D005387:Finland; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D008027:Light; D010507:Periodicity; D011247:Pregnancy; D011272:Pregnancy, Multiple; D012098:Reproduction / Q000502:physiology; D012621:Seasons; D014798:Vital Statistics