Women trying to conceive all want to know the same thing: how likely is it that I will get pregnant? Several factors influence the answer, with the biggest one being age. The older a woman is, the harder it is for her to get pregnant naturally or with fertility treatment. If you’re eager to get to your chances, scroll down. If you’re eager to understand why your chances are the way they are, keep reading. Learn your odds of getting pregnant at 30, 35, 40, and beyond.
Age and Fertility: Getting Pregnant at an Older Age
So what does age got to do with it? In a word, everything.
We know that while men continuously produce new, healthy sperm into their later years (up to their late 50s and beyond), women didn’t get so lucky in the reproductive lottery.
That’s because a woman is born with all the eggs she’ll ever have in life – about 2 million – and she loses eggs all the time. Not only does she lose eggs in the years between birth and the start of her period and during pregnancy and breastfeeding, but she also loses eggs every month as part of her menstrual cycle.
That means that from those 2 million eggs at birth, a woman really only ovulates about 500 eggs during her reproductive lifetime, losing the rest. And just as her egg supply shrinks with time, so does the quality of her remaining eggs. Like the rest of our bodies, eggs cannot escape time-related cellular damage, which results in abnormal eggs that either fail to implant in the uterus, lead to miscarriage or result in an affected baby with a chromosomal condition.
This gradual fertility decline ultimately results in menopause, when a woman’s egg supply is in the hundreds and she no longer has a regular menstrual cycle.
But, as mentioned above, the process does not happen overnight. It’s also not an ‘all or nothing’ mechanism – though the rates of age-related infertility, miscarriage and aneuploidy (a chromosomally abnormal embryo or fetus) go up with a woman’s age, young women can experience these things too, just in smaller numbers.
So what are the numbers then? How likely are you to get pregnant naturally in each decade of your life? How likely is miscarriage as you age? What about your chances of having a chromosomally normal baby? And finally, how successful is IVF as you age? We’ve got you covered. Let’s dive in.
But first, a very important basic premise that underlies all of the above is the genetic makeup of your baby, which is called euploidy (normal) or aneuploidy (abnormal) in scientific terms.
Euploid Embryo vs. Aneuploid Embryo– a primer
Quick biology lesson, here. An embryo can become abnormal if either of its two main parts (the egg or the sperm) is abnormal in some way. Genetically healthy people and babies (and embryos) have 46 chromosomes – 22 pairs of numbered chromosomes and 1 pair of sex chromosomes, indicating the sex of that person.
When an embryo has the correct number of chromosomes (46), scientists call that embryo chromosomally normal, or euploid. If that embryo has 45 or 47 chromosomes, which is not the correct number of chromosomes, scientists call that embryo chromosomally abnormal or aneuploid.
While men’s sperm can stay normal late into their lives, women’s eggs can be abnormal at any point of their reproductive lifespan, but it’s much more common for older women. The older a woman, the more age-related distress her eggs have undergone. This is why as a woman ages, it’s more likely she will have abnormal eggs in her egg reserve, and an abnormal egg will ovulate, leading to an abnormal embryo.
Note: This is not to say aneuploidy cannot come from the sperm – it can – but it more often comes from the egg, especially for couples where the woman is older than 37.
What happens when an abnormal egg ovulates?
Usually, nothing much. If that egg is fertilized by sperm, it usually does not implant inside the woman’s uterus because the body is smart – it can tell the embryo is abnormal.
The normal communication process between embryo and uterus that leads to implantation is disrupted. In this case, pregnancy does not occur. Sometimes the embryo will implant into the woman’s uterus and pregnancy will occur.
However, there will be a breakdown in the pregnancy process due to the abnormal embryo, and miscarriage will occur. This is why miscarriage is so common – 1 in 4 pregnancies end in miscarriage, usually in the first trimester – because the embryo is likely abnormal and fails to progress. However, in rare cases, that abnormal embryo will progress through the pregnancy and result in a baby, but the baby is affected with a genetic condition. The most common of which is Down syndrome, which occurs when a baby has three copies of chromosome 21.
What about normal eggs?
A euploid embryo results when a normal egg ovulates and meets a normal sperm. The chances of pregnancy and implantation and the live birth of a baby are very good with a euploid embryo. This is why fertility clinics now routinely do genetic testing on the embryo to determine if it’s normal or abnormal – that result plays a huge role in achieving success.
That said, neither nature nor science is perfect – pregnancy is a complicated art! – and even euploid embryos don’t always implant or lead to successful pregnancies sometimes. For a fertile young couple, the chances of getting pregnant each month are only roughly 20%. At RMA, the chance of pregnancy following one euploid embryo transfer through IVF is about 69%.
Getting Pregnant at 30, 35, 40, 45
The older a woman, the higher the chance she has abnormal eggs in her egg supply. How old is old?
Well, a woman’s peak fertility is actually in her mid to late 20s, meaning the average woman in that age range has far more normal eggs in her ovaries than abnormal eggs.
As a woman hits 35 years old, however, her aneuploidy rates inches higher, and by the time she’s 37, higher still.
When a woman hits 40, most of her eggs are aneuploid, and when she’s in her early 40s, her aneuploidy rate is so high that her chances of pregnancy and birth, naturally or with In Vitro Fertilization (IVF), are quite low.
The above data summary comes from a landmark study on aneuploidy done by RMA’s Dr. Jason Franasiak, published in 2013. Dr. Franasiak looked at embryo biopsy patient data from IVF patients and saw how the aneuploidy rate climbed with age.
While his data found that aneuploidy rates were also relatively high (over 40%) for 22 and 23-year old women, this is not a natural phenomenon for most healthy young women – the young women included in the trial likely had other fertility or genetic issues. In other words, though this study found young women had high aneuploidy rates, the finding was specific to those in the study and not indicative of aneuploidy trends for young women overall. Meaning, we can assume the younger a woman, the lower her rates of aneuploidy.
Rate of Aneuploidy by Age
- When a woman is 29, about 20% of her eggs will be aneuploid (or abnormal)
- When a woman is 31, about 30% of her eggs will be aneuploid
- When a woman is 35, about 35% of her eggs will be aneuploid
- When a woman is 37, about 42% of her eggs will be aneuploid
- When a woman is 40, nearly 60% of her eggs will be aneuploid
- And when a woman is 44, nearly 90% of her eggs will be aneuploid
Does your chance of getting pregnant decrease with age?
What can we deduce from this data, other than that your chances of pregnancy decrease with age?
Well, we can say that the chance of naturally ovulating a normal egg each month goes way down after a woman is 37 – in fact, her chances of ovulating a normal egg are a little less than 60% each month.
Suppose you think that’s still pretty good. In that case, you’re right – but remember, even normal eggs and embryos don’t lead to a successful pregnancy 100% of the time, so saying the woman has a 60% chance of ovulating a normal egg each month is not the same as saying she has a 60% chance of pregnancy each month – in fact, the figure is much lower (remember a young fertile couple’s chance of pregnancy is only about 20% each month, and that’s assuming the ovulation of a normal egg).
On top of that, the aneuploidy rate increases faster after 37 and very rapidly after 40. Because aneuploidy usually means no pregnancy or a miscarriage, a high aneuploidy rate indicated a low sustained pregnancy rate.
Dr. Franasiak’s data also allows us to deduce miscarriage prevalence among different age groups. Because we know aneuploidy is the leading cause of miscarriage, we can safely assume women in age groups with high aneuploidy rates would also have high miscarriage rates. In other words, the older the woman, the less chance she gets pregnant, and if she does, the higher the chance she’ll miscarry.
Age and Fertility Research
Plenty more, and it reflects the same trend we mentioned above – the younger the woman, the better her chances of a successful pregnancy. Let’s take a look at the data below.
If you look here, you’ll see data from the American Society of Reproductive Medicine (ASRM) on the odds of natural pregnancy by age each month.
|Age (years)||Odds of a Natural Pregnancy by Age each Month|
Below, you’ll see data on the odds of natural pregnancy by age within one year of trying.
|Women’s Age||Chance of Getting Pregnant by Age Within 1 Year|
Hendershot GE, Mosher WD, Pratt WF. Infertility and age: an unresolved issue. Fam Plann Perspect. 1982 Sep-Oct;14(5):287-9. PMID: 6926975.
What if I can’t get pregnant naturally? Will IVF help?
If you are struggling with age or non-age-related infertility (like PCOS or endometriosis), a fertility doctor can help.
The first line of treatment for mild infertility is Intrauterine Insemination, or IUI, which is when a doctor inserts sperm into a woman’s uterus at the time of ovulation in hopes of achieving pregnancy. This can often be combined with medications to increase the number of eggs released at the time of ovulation.
For more advanced cases, and even some mild cases that want to see success quickly, IVF is the treatment option to pursue, as it’s got the highest success rates by far. IVF dramatically improves live birth rates for infertile couples and gives them a chance at family-building.
It is just as shocking as it is for a woman who got pregnant quickly with her first child to discover just a few years later that she has a low ovarian reserve and may not conceive again, either naturally or with IVF. It’s also shocking when that same woman, several more years later, conceives naturally and gives birth to a healthy baby. While these types of surprise success stories are not as common as one would like, they certainly happen. Ask any fertility doctor.