What Women Should Know About Their Biological Clock

For some women, their 20s are a magical time of dating, focusing on career moves, and figuring out who they are and where they belong in the world. For others, however, this is a time of immense pressure to land that marriage proposal, followed by sowing the seeds of a family by the time their 20s are over. While some women have naturally always had the deep desire to have children, there are plenty of women out there who would rather wait until their 30s or even later. In fact, because of the progression of women's roles in society, more and more women are spending longer periods of time without children compared to older generations, who typically began having babies right out of high school or college. Many women think this is linked to the societal norms of different periods in history, but what if there's some biological science connected to having children younger?

Most of us have heard of the term "biological clock," but not all know exactly what it means. Basically, when someone refers to a woman's biological clock, this phrase can be thought of as a hypothetical ticking clock that is counting down to the final timeframe in which she can have children. It can be easy to dismiss the biological clock as an old-school way to keep women steering in the direction of reproducing — as easy as it is to assume that women can effortlessly have babies all the way up until menopause.

Where the idea comes from

The idea that women's fertility could be measured by the ticking of a biological clock was first coined in a 1978 Washington Post article titled "The Clock Is Ticking For the Career Woman." Reporter Richard Cohen shared that most of the women he interviewed about the idea of the biological clock told him they could feel a clock ticking. "Some talked about it in a sort of theoretical sense, like the woman who said she wanted five children and didn't even have a boyfriend yet. She had to get something going, she said, and you could tell that she resented the fact that a deadline had been imposed on her," he reported. In a nutshell, Cohen's article emphasizes how women could feel the pressure to have children everywhere they went — something men would never have to worry about.

Soon after, Boston Globe writer Ann Kirchheimer wrote that "the beneficiaries of the women's movement, a first generation of liberated young ladies ... who opted for careers, travel, independence rather than husband, home, and baby are older now and suddenly the ticking of the biological clock is getting louder and louder" (via The Guardian).

News articles — like Cohen's and Kirchheimer's — began the societal phenomenon of the "glamourization" of working women who were able to juggle a career and children, while women who elected to focus on their career were bombarded with cautions saying that they would regret their decision in the future.

Why the clock doesn't stop at 35

Any pregnancy after a woman turns 35 is medically defined as a geriatric pregnancy. Every woman is born with all of the eggs she will have in her lifetime — close to 2 million — but she will only ovulate 300 to 400 of them between puberty and menopause. As you age, eggs begin to lose quality and eventually die off. In fact, a woman's fertility begins declining in her late 20s and continues to take dramatic dips for the next 10-15 years, with 40-year-old women having only a 5% chance of conception each month. So while pregnancy after 35 is much harder, it's certainly not impossible.

"Many women assume they will have no difficulty getting pregnant until they discover they can't," Rachel McConnell, MD, tells Columbia University Irving Medical Center. "I've had patients say, 'I didn't worry about this because my grandmother had a child when she was over 40.' But your grandmother's or mother's experience doesn't predict what will happen to you." McConnell notes that just because you are a healthy individual who exercises and eats right, it's important to remember that fertility health is a complete entity of its own. Different factors other than physical health will ultimately be the determining factor in your ability to conceive. However, despite the fact that fertility declines dramatically at a certain age, 35 is not an end-all number, and plenty of fertility options can be looked into for anyone having difficulty with conception.

Can you pause the clock?

In past years, the notion of pausing one's biological clock would have seemed totally impossible, but with more women broadening their life's focus, figuring out ways to delay the downfall of fertility has come to the forefront. Because the quality of eggs does decline over time, fertility treatment options like IVF might not be the best option for women trying to conceive past 35. IVF uses a woman's own eggs, so even if she is undergoing treatment, there is still a chance of birth defects and miscarriages, which are mainly caused by older eggs.

One way around the egg aging process is to freeze them, and this can be done years — or even decades — before you're looking to have children. The egg-freezing process begins by starting with a hormonal medication that causes the body to release more eggs than it normally would during a cycle. Then, on the day of the procedure, the doctor uses a fine needle and an internal ultrasound probe to harvest and collect eggs from the ovaries. Finally, the eggs are treated with cryoprotectants to maintain their structure and are frozen into "glasslike" cells to be stored in a cryopreservation tank.

Moreover, in 2019, Israeli researchers announced the discovery of a gene inside worms that is able to control the aging of eggs. Since worms contain the same number of genes that humans do, scientists are hopeful that research can develop further in regards to the gene in humans.

Societal pressure

2021 was U.S. history's slowest year for population growth. Whether this was due to the pandemic or personal desires is up for debate, but the fact that population rates have been declining for decades might tell us something. In fact, unlike in the '70s and '80s, recent surveys, such as one conducted at Pew Research Center, have reported that 44% of childless Americans say they have no desire to ever have kids. What's even more intriguing is that 74% of men and women under 50 with children said that they don't plan to have any more children.

What can this tell us about the pressures from society? In 2016, for the first time ever, more women gave birth in their 30s than in their 20s. Although women who give birth in their '20s are less likely to suffer from pregnancy conditions like preeclampsia and have a higher chance of getting pregnant, mothers in their '30s report that they have "higher energy, better fitness, and fewer aches and pains" compared to women who had babies in their 20s.

From all this research, we can arguably conclude that pressure from society to have children has eased up quite a bit in recent years. Women now have the option to wait until their 30s to have children, and they are beginning to see the possible benefits of this choice — something many women were not able to do in the past.

Not everyone will feel the effects of the clock

Not all scientists and doctors agree on the specific prime age of fertility, but generally speaking, between the ages of 23 and 32 is when fertility is at its maximum potential. Unfortunately, many women's bodies have not yet fully evolved with society's new standards of having kids later in life. So, naturally, some women will feel the tick-tock of their biological clocks at an early age. But some may never feel the urge to have kids, and that's completely normal, too. As psychologist Catherine Aponte explained to Ro, women should "be cautious about metaphors like the 'biological clock' — don't take them literally. The popularity of this metaphor is still strong, and it still supports a traditional view of women."

If you do feel your biological clock ticking but you're not currently in the position to have kids, there are some important things to remember. First and foremost, women should never settle. Oftentimes, a woman will begin to feel the effects of the clock and rush into a relationship or partnership that doesn't feel right just because she desires to have children. Try letting go of the childhood fantasies of what you pictured your life looking like — nine times out of ten, things never turn out the way we planned. If you truly and honestly know that having children is something you wholeheartedly desire, have the courage to be proactive and look into egg freezing before it's too late.

When is the best time to have a baby?

Women are most fertile in their early 20s, but is that the best time to have kids? It depends on who you ask. "We live way longer than our ancestors did," Zain Al-Safi, MD, tells UCLA Health. "The ovaries are designed to be done with reproduction by age 44, 45 maybe. So now that women live longer — like double that age — biology just didn't catch up. For women, we see a gradual decrease in pregnancy rates after age 32, then after age 35 to 37 it becomes more pronounced." Dr. Al-Safi also adds that paternal age makes a difference in fertility as well because the quality and quantity of fertile sperm diminish over time.

But at the same time, people in their 20s are less likely to be in a financially stable position to raise a family. "If you are still quite busy with establishing a career, or haven't found the perfect partner, you shouldn't be pushed into getting pregnant just to have a child," Mary Jane Minkin, MD, shares with Parents. "However, you also need to take into account how many kids you want." For example, some women who only want one or two kids can wait a bit longer to get pregnant, but for those who are set on having a large family, waiting until 32 or 33 might not be the best move. The perfect time to have a baby ultimately depends on numerous personal factors.

Age isn't the only factor in fertility

We all know someone who got pregnant on the first try. We probably all also know someone who has struggled with fertility for years. Though age is the most important factor in fertility, it's most certainly not the only one. There are many factors that come into play when it comes to your chances of getting pregnant. For starters, having a regular cycle will increase your chances of pregnancy. When a woman has regular cycles, she is ovulating once a month; when you ovulate, you can monitor precisely when this occurs with an at-home urine test and try to engage in more intercourse during this time.

Furthermore, many lifestyle factors can play an indefinite role in your fertility. For instance, women who are overweight are less likely to ovulate each month. Obesity is also linked to miscarriage, gestational diabetes, preeclampsia, and other pregnancy complications, but research shows that a drop in even 5% to 10% of body fat can improve chances of fertility. Additionally, women who smoke and take part in recreational drugs are three times less likely to get pregnant quickly compared to women who don't smoke or do drugs.

Some instances of infertility simply come without an explanation, which is called "unexplained infertility." When a woman suffers from unexplained infertility, she typically shows no signs of anything that would cause delays in pregnancy, and all bloodwork, imaging diagnostics, egg count, and their partner's fertility levels all come back normal.

Pregnancy later in life

For some women, getting pregnant in their late 30s and 40s is a breeze, but for others, it can take hard work, time, and money. Advanced maternal age is a term used to describe a pregnancy in a woman over the age of 35. Because of the risks and challenges associated with a woman being older, it is considered to be a high-risk pregnancy that is treated and monitored differently and more closely than an average pregnancy. Some of these risks include a higher likelihood the baby is born with Down syndrome or other genetic disorders, low birth weight, stillbirth, and the probability of needing a c-section. But while there will likely be challenges and obstacles, a healthy pregnancy is more than possible.

But what happens after pregnancy and you give birth? In reality, there are actually plenty of benefits to being an older mom. "We know that people become more mentally flexible with age, are more tolerant of other people, and thrive better emotionally themselves," professor Dion Sommer states. "Psychological maturity may explain why older mothers do not scold and physically discipline their children as much ... thereby [contributing] to a positive psychosocial environment" for their children (via ScienceDaily). "This style of parenting can thereby contribute to a positive psychosocial environment which affects the children's upbringing," he explains. Additionally, scientific advancements with each passing decade give more and more advantages to a child in terms of health, education, technology, and society.

Are you running out of time?

In spite of success stories, statistics, and facts, many aging women still wonder if they are indeed running out of time to conceive. While the pressure of the clock can feel overwhelming, the good news is that major innovations in fertility might be on their way. One such innovation lies in creating eggs and sperm from patients' skin cells. This technique, called in vitro gametogenesis (IVG), has proven to be successful in mice and could allow women to become pregnant at a much later age and allow same-sex couples to produce children who are biologically related to each other.

But what do advancements like this mean ethically? "I don't think the goal should be to enable women to get pregnant into their 60s," fertility expert Marcelle Cedars, MD, explains to UCSF Magazine. "Rather, we want women to have the best reproductive lifespan possible — to be able to have children when they want to and to not have children when they don't want to — and to have a society that supports women across that spectrum." Dr. Cedars adds that by 2050, we may be able to genetically cure diseases in embryos before they're even born. "But will society be ready to accept it?" she asks.

Ultimately, a biological clock isn't definite. There are many factors that play into a woman's fertility, and it's up to every individual to decide when and how to be proactive about their reproductive health.