Relation between semen quality and fertility: a population-based study of 430 first-pregnancy planners

doi:10.1016/S0140-6736(97)10514-1

The Lancet

Volume 352, Issue 9135, 10 October 1998, Pages 1172-1177

https://doi.org/10.1016/S0140-6736(97)10514-1 Get rights and content

Summary

Background

Semen analysis is part of the routine assessment of infertile couples. WHO defines a sperm concentration above 20×10⁶ 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.

Methods

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.

Results

There were 256 (59·5%) pregnancies among the 430 couples: 165 (65·0%) among those with a sperm concentration of 40×10⁶/mL or more and 84 (51·2%) among those with lower sperm concentrations. The probability of conception increased with increasing sperm concentration up to 40×10⁶/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.

Interpretation

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.

Introduction

Semen analysis has been part of the standard diagnostic routine for infertile couples ever since low sperm count was linked to male infertility. The sperm count remains the standard measure, but there is debate about the importance of sperm concentration in male infertility. In a study of 800 fathers in 1951,¹ the lower limit of the normal range of sperm concentration was set at 60×10⁶ spermatozoa per mL seminal fluid. The lower limit has been successively reduced to 20×10⁶/mL,² which was subsequently adopted by WHO as a guideline to diagnose male infertility.³ Routine semen analysis also includes measures of sperm morphology and motility, which may have significant effects on male fertility.⁴

Previous studies of semen characteristics and male infertility were limited because they included only infertile couples or only men who had fathered a child.1, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 Some of these studies did not take account of time gaps between semen analysis and fertility assessment, or lacked information on female infertility and sexual activity. To address these issues, we studied the relation between semen characteristics and the probability of pregnancy for couples who had no previous reproductive experience.

Section snippets

Participants

In 1992–94 we wrote to 52 255 Danish trades-union members (metalworkers, office workers, nurses, day-care workers) aged 20–35 years, who lived with a partner and had no children. Couples were eligible for the study if they had no previous reproductive experience, and now intended to stop contraception and have children. Couples were ineligible if they had ever deliberately tried to have a child, whether successfully or not, if the woman had ever miscarried, had an induced abortion, or given

Participants' and semen characteristics

35 couples of the 430 withdrew from the study before the woman became pregnant (table 1); 20 because of changes to family plans, and 15 because of azoospermia, amenorrhoea, or anovulation. 12 men did not provide a semen sample at enrolment.

Characteristics of semen samples are given in table 2. Paired analysis showed that the mean sperm concentration of frozen follow-up samples was 7·6% lower than that of unfrozen enrolment samples (p=0·17), the mean volume was 14·2% larger (p=0·0001), and the

Discussion

This study has linked semen quality with the probability of conception among first-pregnancy planners. Low sperm concentrations were strongly associated with low likelihood of pregnancy. We set a sperm concentration of 40×10⁶/mL as a reasonable threshold between subfertile and fertile men, since any higher sperm concentration was not associated with increased likelihood of pregnancy. However, the 95% CI around this threshold was broad and included a concentration of 20×10⁶/mL—the upper limit of

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Motility and morphology are crucial factors in determining male fertility. The current gold standard defined by the World Health Organization (WHO) mandates that semen analysis be performed by trained technicians. Despite strict standardization and technical guidelines set by the WHO, variability in semen analysis results remains prevalent owing to human subjectivity. Computer-Aided Sperm Analysis presents a further challenge because of its poor agreement with human analysis. This study aimed to enhance the accuracy of automated semen analysis by introducing a new method for expressing sperm motion and investigating advanced deep neural network architectures to estimate motility and morphology. Initially, we extracted motion information from the VISEM dataset using our novel motion representation technique called MotionFlow, along with shape information. Consequently, motility and morphology neural networks were constructed to exploit transfer learning in other fields to improve performance. These networks ingested motion and shape features and made separate predictions for motility and morphology. The evaluation process utilized a K-Fold cross-validation scheme to determine the mean absolute error (MAE) and maintain objectivity throughout the analysis. The proposed method achieved a greater level of performance than the current methods by attaining MAE of 6.842% and 4.148% for motility and morphology estimation, respectively. The improvement accomplished by this research may pave the way toward a fully automated human sperm quality assessment.
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Heat wave exposure was significantly associated with a reduction in semen quality. The windows of susceptibility during 0–90 days before ejaculation varied across sperm count, motility, and morphology. Our findings suggest that reducing heat wave exposure before ejaculation may benefit sperm donation volunteers and those attempting to conceive.
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Anomalías congénitas (mayores y cualquiera; resultados primarios), parto pretérmino (PPT) y ser pequeño para la edad gestacional (PEG; resultados secundarios), así como la necesidad de inyección intracitoplasmática de espermatozoides (ICSI) para lograr el embarazo (resultado primario en cohorte expuesta frente a controles, resultado exploratorio en cohorte previamente expuesta frente a controles). Los resultados se analizaron mediante regresión logística.
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ArticlesRelation between semen quality and fertility: a population-based study of 430 first-pregnancy planners

Summary

Background

Methods

Results

Interpretation

Introduction

Section snippets

Participants

Participants' and semen characteristics

Discussion

Fertil Steril

Reprod Toxicol

Fertil Steril

Fertil Steril

Fertil Steril

Am J Obstet Gynecol

Fertil Steril

Fertil Steril

Fertil Steril

Reprod Toxicol

Fertil Steril

Reprod Toxicol

WHO laboratory manual for the examination of human semen and semen/cervical mucus interaction

Articles
Relation between semen quality and fertility: a population-based study of 430 first-pregnancy planners