It comes as no surprise that pregnancy causes dramatic changes to a woman’s body as it kicks into overdrive, compensating for the increase in metabolism associated with developing a baby. But what is surprising is that pregnancy may actually have an effect on aging. Whether it may cause accelerated or slowed down aging, however, is still wildly debated. Despite this uncertainty, there may be ways to counteract the possible effects of pregnancy on aging.
In many studies, childbirth is associated with shorter telomere length. Telomeres are repetitive, random base-pair caps at the end of chromosomes. They serve to protect the genes on each chromosome during replication as after each cell replication, the very ends of the chromosomes cannot be replicated. The ends of each chromosome are slowly eaten away at with every cell replication, but because of the presence of telomeres, the genes near the end of the chromosome are preserved. However, because telomeres are shortened with every cell division, there is a limit on the number of proper cell divisions that can occur per each cell line before a cell lineage can no longer divide healthily. Shorter telomere length has been associated with an increase in the overall risk of mortality, as well as morbidity rates for diseases such as cancer and cardiovascular disease (x).
In a study published in the Oxford Academic Journal it was found that on average, women who have had children had 4.2% shorter telomeres. The study utilized data collected from the 1992-2002 National Health and Nutrition Examination Survey. Women between the age of 20 and 44 were surveyed, and their telomere lengths were collected. The study does emphasize that the data does not consider the effects of stress, which has previously been linked to shorter telomere length. This means that women who have children may experience increased rates of cellular aging because of the increased stress associated with caring for children.
Another study published in 2018 utilized not just the length of telomeres as a sign of accelerated aging, but epigenetic DNA methylation age. Epigenetic tags, which work by methylating specific parts of our DNA in order to turn on or off genes, have been shown to be a dependable way to determine age. Just as with telomere length, accelerated epigenetic aging has been linked to increased risk of mortality and morbidity. The research found that the average telomere length was shortened and the average DNA methylation aging rate was increased with every child. Curiously, they did find that during the actual period of pregnancy, women appeared to have a younger-looking DNA methyl age. This only lasted during pregnancy, but after giving birth, they appeared to have aged much faster.
Accelerated DNA methyl aging is not only observed after pregnancy, but also during menopause, inflammation, and other notable transitions throughout a woman’s life. This means that accelerated cellular aging is not just specific to the hormonal changes that occur during pregnancy, which is very different than the hormonal changes observed during menopause. This hints that both physiology and hormonal changes are tied to DNA methyl aging.
It also may help provide a reasoning for why women seemed epigenetically younger during pregnancy, but older afterward. Estrogen and estradiol levels spike all throughout pregnancy, and an increase in these hormones has properties known to maintain telomere length as well as DNA methyl age which may account for the temporary younger cellular age during, but not after, pregnancy.
Despite this evidence showing that pregnancy increases the rate at which women age, there have been studies published that contradict this conclusion. Some have shown that in certain societies and communities, childbirth does not shorten a mother’s telomere length, but instead better preserves it in comparison to women who have not have children. This may point to other factors involved in the changes in the aging process in women. One study suggests this may be a result of stress and the amount of support available for mothers.
A study conducted by Pablo Nepomnaschy followed 75 Kaqchikel Mayan women over 13 years. Contrary to the two aforementioned studies, women who had children were observed to have longer telomeres than women who did not have children. Nepomnaschy explains that it may be because, in Guatemalan societies, mothers are supported by their society, especially in providing care for the children. Children are also seen as Godsends, and so the more children a woman has, the more support she receives. This support provided by the community for new mothers helps alleviate not only the stress associated with caring for a newborn baby but also the energetic cost that many theoretic biologists consider to be a possible culprit in the increased rate of aging in mothers. The study further argues that this reduction in energetic cost on the mother may also play a role in the slowing down of aging.
Another possible factor in play in the slowing down of aging observed in the study is the increased levels of the hormone estradiol during pregnancy. Estradiol is an antioxidant that helps protect cells from the wear caused by natural cell processes. Estradiol is also known to increase telomerase activity. Telomerase is an enzyme that helps maintain telomere length by elongating it. The increased presence of estradiol may be a driving factor in the slower cellular aging observed in the study.
Nepomnaschy’s study also found that women who did not have children in the Mayan society had shorter telomeres. One explanation may be that the increased stress that comes from not having children plays a role in the shortening of their telomeres
There is no definitive explanation for why different studies have come to varying conclusions. But there is one common thread that may play a part in the uncertainty, and that is stress. In many of the studies that have investigated the effect of pregnancy on cellular aging, stress is mentioned as a possible explanation for their results. The good news is that the effects of stress on the rate of aging is well studied, and stress is manageable.
A study published in the Proceedings of the National Academy of Sciences of the United States of America followed 58 mothers and found that increased stress associated with caring for children shortened telomere length. It also emphasized that both perceived and environmental stress is strongly associated with lower telomerase activity and shorter telomeres.
One question remains: is there a proven way to mitigate the effects of stress on aging? The answer is yes. A study led by Dr. Puterman found that exercise is an effective way to buffer the effects stress has on telomere length. In those who exercise, perceived stress no longer had a direct effect on telomere length, so perceived stress no longer correlated with shorter telomere length. This was seen with those that participated in vigorous exercise for at least 14 minutes a day.
Mindfulness meditation has also been shown to increase the activity of telomerase. In mindfulness meditation, one focuses on the current thoughts and sensation felt in the present moment. Although more investigation is still needed to better understand the best implementation of mindfulness to help increase telomerase functioning, it is still a good way to help to try and reverse the possible effects of pregnancy on telomeres.
So for those who are pregnant, or considering having children, the one thing that can be taken away from the varying studies on the effects of aging on pregnancy is that stress plays a role, and that there are ways to help mitigate stress. The fact that there are such varying effects of pregnancy on aging goes to show that it may not just be pregnancy itself. The social support women receive in Guatemala and the possible profound effect it had on aging just goes to show that taking steps towards alleviating stress may help. Whether it’s through exercise, meditation, or seeking out support to help with caring for children, women can take actionable steps to do the best they can with the information we have on this topic.
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