Twinning in one area of New Britain.
D003153:Community Health Services; D005193:Family Planning Services; D005260:Female; D005298:Fertility; D006801:Humans; D007226:Infant Mortality; D008297:Male; D008542:Melanesia; D010060:Ovulation; D010298:Parity; D011247:Pregnancy; D012737:Sex Factors; D014427:Twins