Age and Fertility
What the numbers really mean—without the scare tactics.
The Real Story
- Yes, age matters: Fertility does decline, especially after 35
- No, 35 isn't a cliff: The decline is gradual, not sudden
- Individual variation: Some 38-year-olds are more fertile than some 28-year-olds
- Options exist: Many paths to parenthood at every age
Why Age Affects Fertility
Women are born with all the eggs they'll ever have—about 1-2 million at birth. By puberty, that's down to ~300,000-400,000. Each month, many eggs are lost regardless of whether you ovulate, use birth control, or are pregnant.
Two things happen with age:
1. Egg Quantity Decreases
The pool of remaining eggs shrinks over time. This is measured by AMH (Anti-Müllerian Hormone) and antral follicle count.
2. Egg Quality Declines
This is actually the bigger factor. As eggs age, they're more likely to have chromosomal abnormalities. This leads to:
- Lower fertilization rates
- Lower implantation rates
- Higher miscarriage rates
- Higher rates of chromosomal conditions (like Down syndrome)
📊 The Chromosomal Factor
At age 25, about 25% of eggs have chromosomal abnormalities.
At age 35, it's about 40%.
At age 40, it's about 60%.
At age 43, it's about 80%.
This is why miscarriage rates increase with age—many are due to chromosomal issues.
Fertility by Age: The Real Numbers
20-24
Monthly chance of conception: 25-30%
Chance of conceiving within 1 year: 85-90%
Miscarriage rate: 10-15%
This is peak biological fertility, though often not the ideal time for many people socially, financially, or emotionally. Fertility is excellent, but that doesn't mean you need to start now.
25-29
Monthly chance of conception: 20-25%
Chance of conceiving within 1 year: 80-85%
Miscarriage rate: 10-15%
Fertility remains excellent. Most women in this age range conceive within a year of trying.
30-34
Monthly chance of conception: 15-20%
Chance of conceiving within 1 year: 75-80%
Miscarriage rate: 15-20%
Still strong fertility. The decline is beginning but is gradual. Most women conceive without difficulty. This is the most common age for first births in many developed countries.
35-37
Monthly chance of conception: 12-15%
Chance of conceiving within 1 year: 65-75%
Miscarriage rate: 20-25%
The decline accelerates. Still, the majority of women in this age range conceive, though it may take longer. Seek help after 6 months of trying.
38-40
Monthly chance of conception: 8-12%
Chance of conceiving within 1 year: 50-65%
Miscarriage rate: 25-35%
Fertility is noticeably reduced. Many women still conceive naturally, but time is more precious. Don't delay seeking help if you're struggling.
41-43
Monthly chance of conception: 5-8%
Chance of conceiving within 1 year: 35-45%
Miscarriage rate: 35-50%
Natural conception is still possible but less likely. IVF success rates decline. Donor eggs may be discussed. Time is critical.
44+
Monthly chance of conception: 1-3%
Chance of conceiving within 1 year: 10-20%
Miscarriage rate: 50%+
Natural conception is rare. IVF with own eggs has very low success rates. Donor eggs offer much higher success. Some women do conceive naturally at this age, but it's the exception.
About That "35" Number
You've probably heard that 35 is some kind of fertility cliff. Let's set the record straight:
Where Does 35 Come From?
The data suggesting a sharp decline at 35 comes from 17th-century French birth records—before modern medicine, nutrition, or fertility treatments. Modern data shows a more gradual decline.
Why 35 Still Matters
While it's not a cliff, 35 is roughly when:
- The decline in egg quality accelerates
- Doctors recommend seeking help after 6 months instead of 12
- Prenatal screening becomes more routinely recommended
- Pregnancy is classified as "advanced maternal age" (a clinical term, not a judgment)
💡 The Real Takeaway
Don't panic at 35, but don't ignore it either. If you want biological children and haven't started, it's worth having a plan—whether that's trying soon, freezing eggs, or making peace with other paths to parenthood.
Individual Variation
These are averages. Individual variation is huge:
- Some women have diminished ovarian reserve in their 20s
- Some women remain fertile into their mid-40s
- Family history matters (when did your mother/sisters go through menopause?)
- Lifestyle factors play a role
- Overall health affects fertility
Testing Your Personal Fertility
If you want to understand your individual situation:
- AMH test: Measures ovarian reserve (egg quantity)
- Antral follicle count: Ultrasound counts visible follicles
- FSH and estradiol (Day 3): Hormone markers
Note: These tests measure quantity, not quality. Egg quality correlates with age and can't be directly tested.
What About Male Age?
Male fertility also declines with age, though more gradually:
- Sperm quality decreases after 40
- Takes longer to conceive with older male partner
- Slightly increased risk of miscarriage and certain conditions
- Men can technically father children into old age, but not without impact
The myth that men have unlimited fertility isn't quite true—it's just a slower and less dramatic decline than female fertility.
Options at Every Age
| Situation | Options to Consider |
|---|---|
| Not ready yet, worried about future | Egg freezing (best under 35-37) |
| Trying naturally, under 35 | Give it 12 months, then seek help |
| Trying naturally, 35+ | Give it 6 months, then seek help sooner |
| Struggling to conceive, 38+ | IVF may be more time-efficient than IUI |
| Very low ovarian reserve or 43+ | Donor eggs offer high success rates |
| Any age, open to alternatives | Adoption, fostering, donor gametes |
The Emotional Side
The pressure around age and fertility can be overwhelming. Some thoughts:
- Your worth isn't your fertility: You are more than your reproductive capacity
- Regret is complicated: You might regret waiting, or regret rushing. Neither is certain
- Information is power: Understanding your options helps you make informed choices
- There's no perfect time: Waiting for ideal conditions means waiting forever
- Many paths to parenthood: Biology is one route, not the only route
⚠️ Beware of Both Extremes
Don't let anyone terrify you into decisions you're not ready for. But also don't let anyone convince you that biology doesn't matter at all. Both extremes are harmful. Get the facts, understand your personal situation, and make choices that align with your values and circumstances.
The Bottom Line
Age does affect fertility—that's biology. But it's not a cliff at 35, and individual variation is enormous. If having biological children matters to you, don't ignore age, but don't panic either.
Get informed about your personal fertility, understand your options, make a plan that works for your life, and remember: there are many ways to build a family. 💚