Fredricsson B, Björk G
Fertil Steril. 1977 Aug;28(8):841-5. doi: 10.1016/s0015-0282(16)42738-x.
Morphologic analysis of spermatozoa recovered 10 hours postcoitally from the human female genital tract and its correlation to the clinical situation have shown that (1) spermatozoa in the vagina are equivalent to those in the semen sample; (2) spermatozoa within the cervical secretion exhibit significantly better morphology than do those of the semen sample, indicating the presence of a barrier against abnormal spermatozoa at the level of the external os; (3) this barrier is significantly more effective in cases where conceptions later occur than in cases of persistent, unexplained infertility; and (4) the barrier is particularly active against spermatozoa with abnormal heads.
对性交后10小时从人类女性生殖道回收的精子进行形态学分析及其与临床情况的相关性研究表明：（1）阴道内的精子与精液样本中的精子相当；（2）宫颈分泌物中的精子形态明显优于精液样本中的精子，这表明在外口水平存在对异常精子的屏障；（3）在随后发生妊娠的情况下，这种屏障比在持续性不明原因不孕症的情况下更有效；（4）该屏障对头部异常的精子特别有效。
