Advanced paternity does not affect maternal or foetal health during pregnancy

Within the framework of the 38th Congress of the European Society of Human Reproduction and Embryology (ESHRE)

• Two studies presented by IVI at the 38th Congress of ESHRE confirm that advanced paternal age does not appear to negatively affect the health of mother or foetus during pregnancy
• Health indicators such as gestational diabetes, hypertension, infant weight and head circumference, type of delivery and admission to neonatal ICU (NICU) after birth were analysed as part of each study
• Results will provide reassurance as growing numbers of men delay starting a family

The age at which people are starting to have children is getting later and later. As this number rises, many recent studies have focused on the influence of maternal age on obstetric, gestational and perinatal outcomes, but little is known to date about the implication of advanced paternal age.

Study on the influence of paternal age

This context gives rise to two studies entitled, “Paternal age does not affect obstetric and perinatal outcomes in IVF or ICSI cycles with autologous oocytes” and “Paternal age is significantly related with the type of delivery and the sex of the newborn in IVF or ICSI cycles with donated oocytes”, led by Dr Ana Navarro, researcher at the IVI Foundation, and supervised by Dr Nicolás Garrido, Director of the IVI Foundation. Both studies were presented at the 38th edition of the Congress of the European Society of Human Reproduction and Embryology (ESHRE), held this year in Milan. Their aim was to show whether the obstetric health of a woman during pregnancy was affected if the baby was conceived with sperm from an adult of advanced paternal age. They also sought to find out whether this affected the type of delivery and the health of the infant, and how this influence occurs.

How were the studies designed?

In the first study, data was analysed from 16,118 singleton newborns conceived through IVF/ICSI treatment with a patient’s own eggs at IVI clinics in Spain between January 2008 and March 2022. Paternal age ranged from 18 to 51 years. The fathers were divided into three age groups: under 30 years, 30 – 40 years, and over 40 years.

In the second study, all of the couples used donor eggs. Data was analysed from 16,382 couples who had IVF treatment at IVI clinics in Spain between January 2008 and March 2022. This included information on 17,988 births. Multiple births were excluded from the analysis. Paternal age ranged from 21 to 54 years. The egg donors were aged between 18 and 35 years and had no history of health problems. The fathers were again divided into three age groups: under 30 years (this group had 233 babies), 30-40 years (6,539 babies) and over 40 years (11,216 babies).

“We’ve taken into account a series of pregnancy and perinatal health indicators such as gestational diabetes, hypertension, child weight, type of delivery, head circumference and admission to the ICU after birth. This resulted in the conclusion that paternal age does not affect obstetric and perinatal outcomes in assisted reproduction treatments with a patient’s own oocytes. Despite the fact that several studies suggest the threshold for paternal age to be considered ‘advanced’ is 40 years, we believe it is convenient to revise this limit according to these results,” explained Dr Garrido.

Is there a loss of quality due to advanced paternal age?

The studies specifically examine whether there is a drop in semen quality or a decline in male fertility with age that may influence obstetric and perinatal outcomes. After the analysis was adjusted for maternal age among other variables, the results were not statistically significant. This was the case for treatments with a patient’s own oocytes.

“One of the reasons for this difference between men and women is purely biological. In men, spermatogenesis takes place constantly, every day and at all times. New cells are generated. Women, on the other hand, have ovarian follicles in their ovaries from when they are in their mother’s womb. They are with them all their lives. Obviously, this influences the characteristics of fertilisation and all that it entails afterwards. The sperm cells are not as old as the eggs when fertilisation is attempted,” added Dr Navarro.

Study on the influence of paternal age with donor eggs

One of the advantages of research with donor oocytes, or eggs, is that it allows the female factor to be standardised: the profiles of egg donors are very similar (e.g. age, no history of health problems, etc.).  While analysing the status of pregnancies with donor eggs, a small variation was observed. Pregnancies fathered by men over 40 were 2.3 times more likely to be delivered via caesarean section than those fathered by men under 30. A significant difference in the sex of the newborn was also observed, showing that men over 40 were 20% more likely to have male offspring. Both of these observations remained significant after the adjusted analysis. However, the researchers indicated that the rate of caesarean delivery may not be clinically relevant, since caesarean delivery is a variable that is influenced by personal or medical decisions.

“Starting from the premise that advanced paternal age is understood to mean a male of at least 40 years of age, it is the medical problems associated with ageing that lead to the quality of the semen not being optimal. This is especially true in the case of older ages. It can lead to a somewhat higher risk of disease in the baby, although these are very rare. Male fertility is still a somewhat unknown field in scientific terms. With this mind, that’s why at IVI, we continue to our research on a daily basis to tackle the challenges it presents.

What is really interesting and hugely important, is our finding that the babies born to older fathers were just as healthy as those born to younger men and the pregnancies were just as healthy too,” concluded Dr. Garrido.