Chen Chien-jen, Professor at the Graduate School of Public Health at National Taiwan University, says that one reason for the discrepancy is that women in the West give birth much later (about five years on average for the first birth) than women in the Orient.
台灣大學公共衛生研究所教授陳建仁推測，造成東西方雙胞胎數量差別的主要原因之一，是歐美產婦第一胎的平均年齡約比亞洲地區大五歲左右。