Bonde J P, Ernst E, Jensen T K, Hjollund N H, Kolstad H, Henriksen T B, Scheike T, Giwercman A, Olsen J, Skakkebaek N E
Department of Occupational Medicine, University Hospital or Aarhus, Denmark.
Lancet. 1998 Oct 10;352(9135):1172-7. doi: 10.1016/S0140-6736(97)10514-1.
Semen analysis is part of the routine assessment of infertile couples. WHO defines a sperm concentration above 20x10(6) per mL seminal fluid as normal. We studied the association between semen quality and the probability of conception in a single menstrual cycle in Danish couples with no previous reproductive experience.
In 1992-94, we invited 52,255 trades-union members aged 20-35 years, who lived with a partner and had no children to take part in the study; 430 couples agreed. The couples discontinued use of contraception, and were followed up for six menstrual cycles or until a pregnancy was verified within this period. Each man was asked to provide a semen sample at enrolment (which was analysed without freezing). Women kept a daily record of vaginal bleeding and sexual activity. The association between semen quality and likelihood of pregnancy was assessed by logistic regression, adjusted for sexual activity and female factors associated with low fertility.
There were 256 (59.5%) pregnancies among the 430 couples: 165 (65.0%) among those with a sperm concentration of 40x10(6)/mL or more and 84 (51.2%) among those with lower sperm concentrations. The probability of conception increased with increasing sperm concentration up to 40x10(6)/mL, but any higher sperm density was not associated with additional likelihood of pregnancy. The proportion of sperm with normal morphology was strongly related to likelihood of pregnancy independently of sperm concentration. Semen volume and motility were of limited value in pregnancy prediction.
Our study suggests that the current WHO guidelines for normal semen quality should be used with caution. Some men with sperm counts above the lower limit of the normal range defined by WHO may in fact be subfertile.
精液分析是不孕夫妇常规评估的一部分。世界卫生组织将精液中精子浓度高于每毫升精液20×10⁶个定义为正常。我们研究了丹麦此前无生育经历的夫妇精液质量与单个月经周期受孕概率之间的关联。
在1992 - 1994年，我们邀请了52255名年龄在20 - 35岁、与伴侣同居且无子女的工会成员参与研究；430对夫妇同意参加。这些夫妇停止使用避孕措施，并接受了六个月经周期的随访，或直至在此期间确认怀孕。每位男性在入组时被要求提供一份精液样本（未冷冻进行分析）。女性记录每日的阴道出血和性活动情况。通过逻辑回归评估精液质量与怀孕可能性之间的关联，并对性活动以及与低生育力相关的女性因素进行了调整。
430对夫妇中有256例（59.5%）怀孕：精子浓度为40×10⁶/mL或更高的夫妇中有165例（65.0%）怀孕，精子浓度较低的夫妇中有84例（51.2%）怀孕。受孕概率随着精子浓度增加至40×10⁶/mL而升高，但更高的精子密度与额外的怀孕可能性无关。正常形态精子的比例与怀孕可能性密切相关，且独立于精子浓度。精液体积和活力在预测怀孕方面价值有限。
我们的研究表明，应谨慎使用世界卫生组织当前关于正常精液质量的指南。一些精子计数高于世界卫生组织定义的正常范围下限的男性实际上可能存在生育能力低下的情况。
