A new Israeli study published in the American Journal of Obstetrics and Gynaecology has looked into why Autumn seems to be a very busy time for babies being born. This is one of the first studies to look into seasonal variation in human sperm quality and suggests that Winter and early Spring are the best times for good quality sperm production (from men with ‘normal’ sperm samples).
There were 6447 participants in this study and all were men attending a Fertility Clinic in Israel with their partners between January 2006 and July 2009. Of the 6455 samples collected from these men, 4960 were considered normal samples according to the World Health Organisation (WHO) criteria while 1495 were considered abnormal.
In the group of men with normal sperm, it was found that sperm count and number of faster swimming sperm (the ones that increase the chance of fertilisation) was higher in Winter and early Spring. It was also noted that there were fewer abnormal looking sperm in samples during Winter and early Spring. In order to conclude that the best quality sperm was produced during this time period, the authors of the paper had to take into account that human sperm production takes approximately 70 days. Levitas and colleagues reported a decline in sperm quality from men with normal sperm from Spring-time onwards. Interestingly this seasonal variation did not apply to men with sperm that was considered abnormal.
The authors of the paper suggest that ‘the winter and spring semen patterns are compatible with increased fecundability and may be a plausible explanation of the peak number of deliveries during the Fall’.
Before this, most studies into seasonal variation in sperm quality have been carried out on animal models. Seasonal variation in sperm as seen in animals is thought to be due to changes in sperm production and mating behavior that are dependent on temperature and length of daylight hours. However it is not clear what factor(s) may be the cause of seasonal variation seen in human sperm quality.
Of course, this study only included men attending a single Fertility Clinic and so may not be representative of the natural population. In addition, the differences in climate and lifestyle between Israel and Britain may mean that this data is not reproducible in this country.
Reporting on the findings of this study, many specialists in the field of Fertility would encourage those trying to conceive to do so regardless of the season. Many couples trying to conceive in the natural population however may benefit from fertility treatment.
Here at the Herts & Essex Fertility Centre our results are consistent throughout the year, come rain or shine!
To get more advice on how to improve your fertility or maintain good sperm quality, do call us on 01992 78 50 60 to book an appointment with a member of our team.