Families are like fruit trees.
The best time to start one is 20 years ago.
The second best time is now.
They Have Fewer Kids than They Want
Most Americans… and Europeans… and Asians… and so on have fewer children than they wanted.
You can find that out by talking to people who've finished their families. You can find that out by talking to people who have fertile years left and compare what they would like to happen with what realistically will.
Or you can delve into a whole host of studies.
https://www.mic.com/life/falling-birth-rates-childfree-millennials-genz
Evolving Fertility Goals and Behaviors in Current U.S. Childbearing Cohorts - Guzzo - 2023 - Population and Development Review - Wiley Online Library
MoreBirths has been banging this drum pretty hard.
How Fertility Works
One of the main reasons for this mismatch? Modern men and women both don't understand fertility very well and really really don't understand that IVF on average only helps a little.
A new study spells it out. The study took conception data from. American women in the 1960s and 1970s, combined it with contemporary data about the effectiveness of in vitro and other fertility treatments (“IVF”), combined it with data about rates of disease/accidents/reproductive problems that put a stop to childbearing, and then ran a simple mathematical model.
Think of it as running a retirement planner based on historical rates of return.
If you want really good odds (90%) of having a moderate-sized family of three children by purely natural means, be married and procreating by age 23. Shell out for IVF (and other fertility treatments) and put up with the hassle of it, you raise that to age 28. If you want really good odds of having any children at all, 32 is your age. Expensive IVF only raises that age to 35. (Remember, 1 and 2-child families are below the replacement rate.)
From the study
IVF makes a difference but not much of one.
From the study
Let's say you are just a nice American couple, all you want is a boy and girl, you are not weird.
If you want better odds than a coin toss, you need to plan on 3 kids. But 1 out of every 4 couples who have 3 kids will only have boys or only have girls. If you want really good odds, at least 90%, you need 5.
What if you want a big family?
They didn't calculate that. maybe it would have been too depressing. A rough straight-line extrapolation says extremely high odds of having a moderate-sized family of 4 kids means the rings are on the fingers and the pills and condoms are in the trash by the time a woman is 20. For a biggish family, 5 children, where you have a really solid odds of having at least one boy and at least one girl, 17.
We don’t really believe that 17 number. Remember, this is not a direct longitudinal study. There are errors and assumptions. We think that needing to start at age 17 is an exaggeration, the odds are better than that for those who start young. Colonial American and Amish fertility, both 6-8 TFR, had average female marriage ages of 20-22. But perhaps the odds are not better by much.
You can't retire a millionaire by starting to save when you are in your 40s or 50s. You can't get a big, warm, happy family by waiting until your biological clock is screaming for it in your 30s. The late 20s are called the late 20s for a reason--that's late.
Get married, have sex, have kids.
Already Done. You are Preaching to the Choir
All right, two things. First, don’t make assumptions on continued fertility because its been easy so far. If having kids has been relatively complication free, you just have sex, conceive, have a pregnancy, and get birth, you should probably keep going. This is a gift. It won’t last forever and some people never even get the chance.
Second, yes, you probably already know this information about fertility windows. Your naive friends don't. Your children and grandchildren don't either. maybe its up to you to tell them. What your naive, uninformed friends and your progeny need to know:
high odds of having at least three kids without IVF if they start in their early to mid-20s
IVF is expensive, difficult, and doesn't make a huge difference. It's worthwhile for some but is not a gamechanger.
If they want better than even odds of having a boy and a girl, they need to plan on at least 3 children. 4-5 children if they want high odds.
women's fertility declines begin in the 20s
You Can Improve Your Odds
This study's projections are averages. You can beat the odds.
Start early. Women's fertility declines less slowly when the first births are in the late teens to early 20s.
Good nutrition and good health. Most Americans have terrible diets, even in the 60s and 70s. Its worse now. Animal fats, animals proteins, avoid foods that cause inflammation in your experience, avoid processed foods.
Avoid hormonal contraceptives even prior to the desired child-bearing period.
Marry someone with a similar demographic background. Scientists have repeatedly concluded that the ideal fertility levels are between a man and a woman who have genetic similarity equivalent to 3rd or 4th cousins.
Avoid C-sections if at all possible. Rates of c-sections vary wildly from hospital to hospital.
Love each other, reduce the wife's burdens outside the home. Fertility rates go up when the wife is into her husband and when she isn't highly stressed. Getting married while off hormonal contraception will help with this.
Nurse to allow some spacing between birth. For most women on average spacing of about 2 years between births combined with good health and good nutrition maximizes total fertility. Though there are plenty of families with one or two or more closer births who pulled it off.
Learn Natural Family Planning. Most non-Catholic women who have learned it have been really grateful for the enhanced understanding of themselves and their fertility
What If I'm already past my early 20s?
Go for it anyway. You may not have extremely high odds of success, but your odds are much better than if you don't try. Late marriage, IVF, whatever it takes--give yourself a real shot at that happiness. Everyone loves adventure stories about beating the odds, especially if there's some sex hinted at. For you the sex and the adventure where you try to beat the odds are one and the same.
There are plenty of instances of couples having children naturally after conceiving via IVF. Or after unsuccessful IVF. Or after just giving up. Marry, have sex, eat well, exercise, love each other, be happy.
But what about that important bonding time without children in our first few years as a couple?
Myth.
But I knew this one girl, she didn't get married until past 30 and her husband was a great guy and she had 6 kids, no problem
Is your retirement plan winning the lottery?
From my own experience, I can only recommend to start early with having children. I was late to the party. This has a lot of disadvantages. Most likely, you are not as fit anymore, if you are older. If you have kids, you have to be fit to have a lot of fun frolicking with them. In addition, the grandparents are not that old and can spend quite a few years with their grandchildren, which should be benefial for both parties.