For the first time, researchers have identified a specific link between common defects in sperm and an increased risk of pregnancy complications, as well as negative outcomes for the baby. A study conducted by Lund University in Sweden has found that a high percentage of sperm with DNA strand breaks significantly increases the risk of preeclampsia in women who conceive through in vitro fertilization (IVF). This defect also raises the likelihood of premature birth.
Infertility is a growing concern globally, with the number of IVF procedures rising steadily. It has long been known that pregnancies achieved through assisted reproduction techniques carry a higher risk of preeclampsia, recurrent miscarriages, and premature birth, often resulting in lower birth weights. However, the specific causes behind these risks have remained unclear—until now.
“Before IVF, a man’s sperm sample is typically analyzed for concentration, motility, and morphology. However, some men with normal sperm according to these tests still face fertility issues,” explains Amelie Stenqvist, a lecturer at Lund University and specialist in gynecology and obstetrics at Skåne University Hospital, Malmö.
Recent research has shown that 20-30% of fathers whose children are born through IVF have sperm with damaged DNA, indicated by elevated levels of DNA fragmentation. The DNA fragmentation index (DFI) measures the amount of strand breaks in sperm DNA and is a key indicator of male fertility. While sperm with DNA damage can still fertilize an egg, the chances of successful conception are reduced, and a DFI over 30% almost eliminates the possibility of natural conception.
Though advancements in IVF have enabled men with high DFI to father children, little has been known about how sperm DNA fragmentation affects pregnancy and infant health. Part of the challenge is that DFI measurements are not routinely included in fertility assessments in Swedish clinics, and research requires large study populations and access to national health data.
“Since half of the placenta’s genetic material comes from the father, and placental development is central to conditions like preeclampsia, we wanted to explore whether sperm DNA damage could influence this risk,” explains Professor Aleksander Giwercman, a reproductive medicine expert at Lund University and Skåne University Hospital. Giwercman, a co-researcher on the study, led a comprehensive investigation of 1,660 children conceived through IVF and intracytoplasmic sperm injection (ICSI) at the Reproductive Medicine Centre in Malmö between 2007 and 2018.
The findings revealed that among 841 couples undergoing IVF, those with a DFI above 20% faced double the risk of the mother developing preeclampsia (10.5%), as well as a higher likelihood of premature birth. In contrast, couples with a DFI below 20% had a preeclampsia risk comparable to natural pregnancies (4.8%). Notably, no such link was found in cases of ICSI, a procedure where a single sperm is injected directly into the egg.
The study’s implications extend beyond pregnancy complications, as DNA fragmentation in sperm is closely linked to the overall health of the father. Factors contributing to DNA damage include oxidative stress, aging, smoking, obesity, and infections. Many of these are treatable conditions, suggesting that interventions to reduce DNA fragmentation could improve both male fertility and pregnancy outcomes.
“The next step is to identify which groups of men respond best to treatments that prevent sperm DNA damage, with the goal of reducing pregnancy complications,” concludes Stenqvist.
This groundbreaking research offers new insights into male fertility and could pave the way for improved treatments in assisted reproduction, potentially reducing risks for both mothers and babies.
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