Many women today choose to have children later in life for various personal and professional reasons. However, terms like “advanced maternal age” and the idea of a biological clock may raise questions: when does fertility start to decline, and why does it happen?

How Age Impacts Female Fertility

Women are born with a set number of eggs, which decreases in both quality and quantity as they age. While maintaining a healthy lifestyle can boost the chances of conception and a healthy pregnancy, it cannot fully counterbalance the effects of aging on fertility.

On average, women in their early to mid-20s have about a 25–30% chance of becoming pregnant in any given month. Fertility begins a gradual decline in a woman’s early 30s, and the process accelerates after age 35. By the age of 40, the monthly chance of conception drops to approximately 5%.

Why Fertility Declines in Women

Unlike men, who produce sperm continuously, women are born with a finite number of eggs. At birth, this number ranges between one and two million, but by the time puberty hits, only 300,000 to 500,000 eggs remain. Throughout a woman’s reproductive years, she loses several eggs each month.

It’s not just the quantity of eggs that diminishes over time—the quality also declines. By the ages of 45 to 50, many of the eggs left in the ovaries may have chromosomal abnormalities, making them difficult to fertilize. Even if fertilization occurs, some eggs may not implant successfully in the uterus, and a significant portion of pregnancies may end in miscarriage, particularly in the first trimester.

Age and IVF Success Rates

In vitro fertilization (IVF) can assist couples struggling with conception, but a woman’s age also influences IVF outcomes. Here are the percentages of live births per egg retrieval by age group:

• Under 35: 41.3%
• Ages 35-37: 29.7%
• Ages 38-40: 18.2%
• Ages 41-42: 9.1%
• Over 42: 3.1%

The Connection Between Age and Pregnancy Complications

As women age, the risks of pregnancy complications increase. This includes a higher likelihood of chromosomal abnormalities in babies, as well as complications during pregnancy and delivery, such as gestational diabetes, placenta previa, cesarean sections, and stillbirth.

Why Male Fertility Declines 

Although men continue to produce sperm throughout their lives, the quality of sperm deteriorates over time.

Several factors contribute to reduced fertility in men as they age:

• Hormonal changes: Testosterone production decreases, affecting fertility.
• Oxidative stress: This can damage sperm quality.
• Sperm production: The rate of sperm production slows.
• Vas deferens: The tubes that transport sperm can narrow with age.
• Blood flow: Decreased blood supply to the pelvic area may reduce sperm delivery.

In addition to age, lifestyle factors such as poor diet, obesity, and exposure to environmental toxins can impact male fertility.

Tips to Support Fertility After 35

If you’re trying to conceive later in life, there are ways to help optimize your fertility:

• Maintain a healthy diet and regular exercise to support overall wellness.
• Limit caffeine intake to 200 milligrams per day or less.
• Consider taking a prenatal vitamin and supplements that promote egg and sperm health.
• Avoid nicotine, cannabis, and excessive alcohol.
• Reduce exposure to environmental toxins and manage stress levels.

What to Do If You’re Struggling to Conceive After 35

If you’re over 35 and have been trying to conceive for six months without success, or over 40 and trying for three months, it’s a good idea to consult your OB-GYN or midwife. They can help you explore your fertility options and create a plan moving forward.

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