Department of Epidemiology and Population Studies, Jagiellonian University Medical College, Krakow, Poland.
Am J Hum Biol. 2011 Jul-Aug;23(4):560-2. doi: 10.1002/ajhb.21177. Epub 2011 May 4.
This study evaluated changes in breast size during pregnancy depending on infant sex. Due to larger nutritional needs during lactation, male infants may stimulate greater changes in maternal breast size than female infants.
Data were collected by an online questionnaire survey of 120 women from Poland, who had at least one child.
Changes in breast circumference during pregnancy were associated with the infant's gender. Surprisingly, mothers of female infants had greater breast circumference changes than the mothers of male infants (P = 0.03).
The observed difference is surprising in the light of studies reporting that mothers of male infants produced milk that had greater energy content. However, breast size alone does not determine the quality and quantity of produced milk. It is suggested that the larger difference in breast size for mothers of female infants results from a trade-off between direct energy allocations to the growing fetus and to breast enlargement. Perhaps, as in other primates maintaining sexually attractive attributes during pregnancy, early breast enlargement in women is a primary sexual stimulus. The ultimate function of early breast enlargement may function to ensure greater involvement from partners, which is especially important to mothers expecting daughters, who might be in poorer nutritional condition, as predicted by Trivers-Willard hypothesis.
本研究评估了婴儿性别对孕期乳房大小变化的影响。由于哺乳期的营养需求更大，男性婴儿可能比女性婴儿更能刺激母体乳房大小的变化。
研究数据来自对波兰 120 名女性的在线问卷调查，这些女性至少有一个孩子。
妊娠期间乳房周长的变化与婴儿的性别有关。令人惊讶的是，女婴母亲的乳房周长变化大于男婴母亲（P = 0.03）。
鉴于研究报告称，男婴母亲的乳汁能量含量更高，因此观察到的差异令人惊讶。然而，乳房大小本身并不能决定乳汁的质量和数量。有人认为，女婴母亲的乳房大小差异较大，是因为直接将能量分配给胎儿生长和乳房增大之间存在权衡。也许，与其他灵长类动物在怀孕期间保持性吸引力特征一样，女性早期的乳房增大是一种主要的性刺激。早期乳房增大的最终功能可能是确保伴侣的更多参与，这对那些预计会生女儿的母亲来说尤为重要，正如特里弗斯-威尔德假说所预测的那样，她们的营养状况可能较差。
