A recent study conducted by University of Manchester scientists has uncovered intriguing insights into how maternal age impacts fetal development in mice. Published in the journal Reproduction, this research sheds light on why older mice tend to produce offspring with reduced growth potentials.
Oxidative Stress: A Key Player
The study highlights that placentas from older female mice are more prone to oxidative stress, a condition characterized by an imbalance between free radicals and the body's ability to neutralize them. Oxidative stress has been linked to various pregnancy complications, including fetal growth restriction and preeclampsia, both of which elevate the risk of stillbirth. Specifically, the study revealed noteworthy findings:
- Male Offspring: Placental damage was notably heightened in male offspring, displaying increased cell damage due to oxidative stress.
- Female Offspring: Although there were some reductions in fetal weight, the placental alterations observed were not as pronounced as those seen in males.
Weight Reduction and Mitochondrial Function
Interestingly, the research demonstrated that both male and female fetuses from older mice presented reduced weight. This weight reduction was associated with alterations in placental mitochondria, which are essential for cellular energy production. The key findings regarding mitochondrial function are as follows:
| Sex of Offspring | Weight Reduction | Mitochondrial Activity |
|---|---|---|
| Male | Significant weight reduction | Increased oxidative stress |
| Female | Moderate weight reduction | Higher mitochondrial numbers, lower activity |
Future Directions for Research
The researchers are now extending their investigations to include human subjects, specifically looking at placentas from mothers classified as having advanced maternal age (AMA), defined as age 35 and older. Dr. Michelles Desforges, the lead author of the study, noted the importance of understanding sex-specific placental dysfunction, as these mechanisms could provide insights into pregnancy risks associated with maternal age.
“Evidence that sex-differentiated placental dysfunction occurs across various risk groups—including diabetes or obesity—has existed, but our findings uniquely delve into the specific processes related to advanced maternal age,” – Dr. Michelles Desforges.
Understanding these processes is vital as societal trends indicate that pregnancies among older women are increasingly common. In the U.K., for example, the proportion of births to women aged 35 and over has risen substantially from just 6% in 1980 to approximately 25% today.
Conclusion
While advanced maternal age can pose increased risks for certain pregnancies, it is crucial to recognize that many mothers aged 35 and above still experience healthy pregnancies and deliver healthy babies. Future studies will be crucial for developing therapeutic strategies aimed at preventing complications such as fetal growth restriction and stillbirth associated with advanced maternal age.
Further Reading
For more detailed insights, you can access the original study by Jessica Dalton-O'Reilly et al., titled Sex-specific alterations in placental mitochondria, oxidative damage and apoptosis in mice of advanced maternal age, published in Reproduction (2025).
References
[1] Desforges, M., et al. (2025). Sex-specific alterations in placental mitochondria, oxidative damage and apoptosis in mice of advanced maternal age. Reproduction.
[2] Medical Xpress. (2025). Why older mice have smaller offspring—and how sex may play a role. Retrieved from https://medicalxpress.com/news/2025-11-older-mice-smaller-offspring-sex.html.
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