Does sperm size and shape impact fertility outcomes after assisted reproduction?

This study investigated the effect of sperm morphology (SM; size and shape of sperm) on fertility outcomes in couples undergoing fertility treatment. 

They found that abnormal SM is associated with poorer fertility outcomes. 

Male infertility (MI) is a common cause of infertility. Reduced sperm concentration and motility (movement) are common features of MI. Abnormal sperm morphology (SM) is also found in men with MI. SM describes the shape and size of sperm cells. If the shape is abnormal it suggests the quality is lower. Abnormal SM can affect also affect motility. 

Assisted reproductive techniques (ART) can be used to treat MI. Intracytoplasmic sperm injection (ICSI) is a type of ART. It involves selecting the best quality sperm and injecting it into the oocyte (egg). Some labs use sperm motility as an indicator of sperm quality. Some studies suggest that SM may be a better indicator. It is unclear is SM affects fertility outcomes in couples undergoing ICSI. 

This study included 741 ICSI cycles from 666 couples. All couples underwent ICSI with donated oocytes. Each cycle was grouped according to SM. SM is described as the percentage of normal form (NF) sperm. An NF of 5% is considered to be normal. Less than 4% is considered abnormal. Patients were grouped according to NF. Group 1 had a SM of less than 4%. Group 2 had a SM of 4-6% and group 3 had a SM higher than 6%. Fertility outcomes were compared between the groups. This included fertilization rate (FR), clinical pregnancy rate (CPR), and live birth rate (LBR).

Lower SM was associated with poorer sperm concentration and motility. FRs, CPR, and LBR were higher in group 3 compared to the other groups. 

The authors concluded that abnormal SM was associated with poorer fertility outcomes in couples undergoing ICSI. 

This study was based on medical records. There was no information on sperm DNA damage. This could also affect fertility outcomes. More studies are needed.