Is it better to have kids when you’re young or wait until you are older? While previous studies show that kids of older moms are well-adjusted and had better social and language skills, the negative factors linked with delaying childbirth are also evidenced, such as energy and health. Pregnancy and childbirth can be harder for older mothers than for younger moms but advanced medical care mitigates the risks in the developed world.
Maternal effect senescence
Recently, a team of researchers from Woods Hole Oceanographic Institution found that the offspring of older moms are not as healthy or don’t live as long as those of younger mothers. They also have fewer offspring themselves compared to offspring of younger moms. The team discussed maternal effect senescence, which is the decline of offspring quality with increasing maternal age. Despite the negative impact of maternal effect senescence on fitness, it is common in animals.
Christina M. Hernández and colleagues created a matrix population model to better understand how maternal effect senescence may evolve. These models calculate the selection gradients on fertility and survival as functions of maternal age. They then estimated the parameters with information from an aquatic invertebrate, Brachionus manjavacas (Rotifera).
Older maternal age lessens the evolutionary fitness of offspring
The study of microscopic invertebrates tested the evolutionary fitness offspring born from older mothers in several simulated and real environments, including laboratory culture, with less food supply, or under the threat of the predation in the wild. They confirmed that older maternal age does lessen the evolutionary fitness of offspring regardless of the environment it grows. The primary reason is reduced fertility during their peak reproductive period. Hernández and the team also suggest the evolutionary mechanism of why it may happen.
Kristin E. Gribble from the Marine Biological Laboratory and Hernández led the study. Gribble told Phys.org that their research is unique as it combines mathematical modeling and laboratory data from their previous work to answer the long-standing question in the evolution of aging. Why do we observe the phenomenon across many species despite knowing that natural selection can weed out the less-fit offspring? Hernández said it is because the selection pressure declines as mothers age. This is why the less-fit offspring are not removed from the population across different species.
Gribble adds that maternal effect senescence will continue to evolve and persist in the population despite resulting in decreased fitness. The authors said that the models they developed can be applied to a wide range of species in evaluating the fitness consequences of older maternal age. As long as the research will have experimental data on fecundity and lifespan of offspring from mothers of different ages, they can address the question in other organisms.
They also mentioned that advanced maternal age has negative effects on offspring health, fertility, and lifespan in humans. Offspring from older moms have lower reproductive success and shorter lives or both, they wrote. Field studies on species of birds and other mammals also show that offspring from older parents show lower recruitment and survival includes. Producing high-quality offspring that prosper and live longer should offer a selective advantage, they went on.
A 2019 study by Martha J. Bock and the team also focused on how maternal age alters offspring fitness, lifespan, and lifespan extension under caloric restriction.
Age of mothers at childbirth
The Organization for Economic Co-operation and Development, an intergovernmental economic organization founded to stimulate economic progress and world trade, shares that the average age in most OECD countries at which women give birth stands at 30 or above. Only in one OECD country, which is Mexico, is the main age of women at childbirth stands at 28 or less. The mean age of mothers at birth is shown both for first births only and for all births.
Why people postpone parenthood
In another study, which appeared in Oxford Academic’s Human Reproduction Update, Melinda Mills et al said that people were increasingly able to control their reproduction with the introduction of pills and other reliable contraceptive methods. The availability of these contraceptive methods offered the world female emancipation as more women were able to depart from occupying exclusively the mother role and the aspects of reproduction. Career opportunities and employment also opened for women so they could choose between motherhood and other activities. These altered the pattern of reproductive behavior.
In 2013, countries with the highest share of married women ages 15 to 49 whose need for family planning is satisfied includes Thailand (89.2%), North Korea (89.8%), Zimbabwe (86%), Paraguay (82.6%), and Mexico (80.9%). Meanwhile, higher education of women is linked with lower fertility. The second aspect of women’s rising empowerment is labor force participation in society. This led to a decline in the number of kids that women have.
The benefits of youth
Jenn Savedge from the University of Strathclyde said that among the perks of having children at a younger age is that younger women ten to have an easier time with childbirth. They bounce back from pregnancy more quickly compared to older moms. As they begin trying to have kids in their younger years, younger mothers also have fewer fertility issues and even if these arise, they have more time to weigh options. They can have more time to enjoy motherhood and maybe even grandmotherhood. It increases their chance that their children will have a stronger and longer relationship with their grandparents and even great-grandparents. Savedge was not involved in the studies mentioned.
Benefits of having children later in life
On the other hand, there are also benefits to having children later in life. While giving birth may be the downside, older moms tend to be more patient with their children. Studies also show that having kids later in life can make one mentally sharper. The study found a link between having a baby at a later age and brainpower.
It can be scary to think that we have a ticking biological clock. It is also true that women’s number of eggs decreases as they get older. Nevertheless, it would be a good idea to consult with a doctor about family-building plans to ensure that one makes the right choices for their health and life.