For the first time, researchers have linked specific and frequent defects in sperm to the risk of pregnancy complications and negative effects on the baby’s health. A study from Lund University in Sweden shows that a high proportion of the father’s sperm containing DNA strand breaks is associated with double the risk of preeclampsia in women who have become pregnant through IVF. It also increases the risk of the baby being born prematurely.
Infertility is a growing problem and the number of in vitro fertilization procedures is increasing rapidly. It is already known that women who become pregnant through assisted reproduction techniques have a greater risk of suffering from preeclampsia, repeat miscarriages, and the baby being born prematurely and with a lower weight. However, the reasons behind this have not been fully understood.
“Before a planned in vitro fertilization, the man’s sperm sample is analyzed for concentration, motility and morphology. But there are men who, according to this analysis, have normal sperm, but still have reduced fertility,” he says. Amelie Stenqvist, professor at Lund University. University. She received her PhD in Lund and now works as a specialist in gynecology and obstetrics at Skåne University Hospital in Malmö.
About 20 to 30 percent of babies born through in vitro fertilization have parents with damaged DNA in their sperm, as evidenced by elevated levels of DNA fragmentation. The DNA fragmentation index (DFI) is a measure of the number of strand breaks in DNA and is used to provide important new information about male fertility. Sperm with DNA damage may still be fertile, but the chances of fertilization are lower and if the DFI percentage exceeds 30 percent, the chances of natural conception are close to zero.
Although current in vitro techniques allow men with a high DFI to become fathers, until now very little is known about the impact of DNA fragmentation on pregnancy and the health of the baby. It has been difficult to research the topic because the DFI value is not included in the standard measurements currently taken by fertility clinics in Sweden. It also requires a large study population and access to national medical records.
“Since half of the placenta’s DNA comes from the father and placental development and function play a central role in preeclampsia, we wanted to investigate whether a high percentage of sperm DNA damage affected the risk of preeclampsia,” says Aleksander Giwercman.
He is a professor of reproductive medicine at Lund University, a consultant at Skåne University Hospital in Malmö and one of the researchers behind ReproUnion**. Aleksander Giwercman also led a research study that included 1,660 children conceived through IVF and ICSI at the Malmö Center for Reproductive Medicine during the period 2007-2018*.
The results showed that in the 841 couples who underwent IVF, a DFI of more than 20 percent doubled the woman’s risk of developing preeclampsia (10.5 percent) and also increased the risk of preterm birth. In the IVF group with a DFI less than 20 percent, there was a 4.8 percent risk of preeclampsia, which is comparable to naturally occurring pregnancies. For couples undergoing ICSI, there was no association with preeclampsia.
“Today, DFI analysis is only performed in some fertility clinics in Sweden, but we believe it should be introduced as standard in all clinics. It can give couples answers about why they do not get pregnant and can influence the method chosen Not only that, our latest results show that DFI analysis could be used to identify high-risk pregnancies,” says Aleksander Giwercman.
What makes this finding even more interesting is that high DNA fragmentation in sperm is related to the father’s overall health and is potentially treatable. Most DNA damage is caused by oxidative stress, which is an imbalance between harmful molecules and antioxidants that protect cells. Other factors that increase DNA fragmentation include a man’s age, smoking, obesity and infections.
“The next step is to identify which group of men respond best to methods to prevent and treat sperm DNA damage and test these methods to prevent pregnancy complications,” concludes Amelie Stenqvist.