What Research Says About Pregnancy at 35+

Hillary Bennetts

What Research Says About Pregnancy at 35+

Table of contents

  • Intro
  • Risks
  • Benefits
  • So What Can You Do?
  • You Don't Age Overnight

0 min read


Our previous post about supporting pregnancy at age 35+ was a favorite. We know this is a topic that resonates with many of you (us too!) and so we wanted to follow it up with some more evidence-based information about pregnancy beyond age 35. 

There can be a great deal of misinformation and fear about the risks associated with pregnancy in the late 30s and beyond. So we want to address these true risks while weighing them against some potential benefits of pregnancy at 35+. We’ll also provide some actionable tips for how you can best prepare for your pregnancy so that you feel empowered with information to start your family whenever it feels right to you.


Fertility Decline

Research shows that fertility decline starts at age 32 and progresses more rapidly after age 37. This decline is largely due to egg quality, as a woman’s healthier eggs tend to be used first. Once a woman reaches her late 30s and early 40s, the number of high quality eggs that are able to be fertilized are fewer. That does not mean a healthy pregnancy isn’t feasible, it just means it may take a bit longer to achieve.

One study reported in an American College of Obstetrics and Gynecology (ACOG) journal followed women with sterile partners through artificial insemination over 12 menstrual cycles. After 12 months, the following statistics were recorded: 

  • Women less than age 31: 74% got pregnant 
  • Women age 31-34: 62% got pregnant 
  • Women 35 and over: 54% got pregnant

Another study evaluated fertility declines in IVF patients. The percentage of IVF cycle starts that resulted in live births were as follows:

  • 41.5% in women younger than 35 years
  • 31.9% in women aged 35–37 years
  • 22.1% in women aged 38–40 years
  • 12.4% in women aged 41–42 years
  • 5% in women aged 43–44 years
  • 1% for women older than 44 years  

In contrast, in patients who used eggs obtained from healthy, younger donors, 51% of fresh transfers resulted in a live birth, regardless of the age of the recipient.


The rate of miscarriage (spontaneous loss of a woman's pregnancy before the 20th week) climbs gradually with age. Research estimates the spontaneous miscarriage rate as follows:

  • 9% at age 22 
  • 18% at age 30 
  • 20% at age 35 
  • 40% at age 40 
  • 84% at age 48

It’s important to note that this increase is not due to a woman’s ability to carry a baby. Rather, it is due to egg quality. Again, as a woman ages, she has fewer eggs that are viable for a healthy pregnancy. While losses are terribly painful, it can be comforting to know that your body is still well equipped to carry a baby, and simply trying again may result in a higher quality egg being fertilized.

Genetic risks 

Age is a strong predictor of Down Syndrome and other chromosomal abnormalities. Large population-based trials, as well as in-vitro fertilized embryos, estimated the risk of down syndrome at 16 weeks as follows:

  • 1 in 1,120 at age 25 
  • 1 in 733 at age 30 
  • 1 in 265 at age 35 
  • 1 in 60 at age 40 
  • 1 in 23 at age 45 

For this reason, many women age 35+ opt for genetic screening, which is a simple and highly accurate predictor of genetic defects. These tests can be performed as early as 10 weeks.


Stillbirth is the loss of a baby at or after 20 weeks of pregnancy. The increased risk in women 35+ is slight and has decreased over the past several decades thanks to modern research and technology. In addition, the risk is decreased if a woman 35+ has already had a baby - it is actually less in a woman 35+ who has already had a baby than in a first time mom who is under 35! Here’s how the data compares:

The other good news is that stillbirth is a risk that is more influenced by other factors than the other risks of pregnancy at age 35+. The following are other factors that increase risk of stillbirth. Many of these can be managed and mitigated:

  • Being pregnant with your first baby 
  • Body mass index ≥ 30 
  • Preexisting diabetes
  • Chronic high blood pressure 
  • Smoking
  • Alcohol use 
  • Having a pregnancy using assisted reproductive technology 
  • Being pregnant with multiples 
  • Male fetal sex 
  • Placenta previa
  • History of a previous stillbirth


While the risks of pregnancy at 35+ can seem somewhat intimidating, the truth is, there are always risks associated with pregnancy, and there are also benefits to delaying pregnancy until later in life that may balance out the increased risks for many women.

Research shows that women age 35 and over are more likely to breastfeed their babies than women under age 35. This is most certainly a benefit, as there are notable gains to both mama and baby that come with breastfeeding. 

This increased rate of breastfeeding may be due to a number of factors, including women age 35+ having a better understanding of the benefits of breastfeeding, having a more established partnership at home to help support the journey, and having a career more conducive to pumping at work.

There are also significant benefits to many women and men of delaying parenthood. The decision to wait to have a baby means that you have years in your life to accomplish other things that can benefit you in the long term. Delaying pregnancy into the 30s and 40s may provide a couple a number of benefits:

  • More emotionally ready to start a family
  • More established a stable relationship long-term partnership
  • More financially established and able to support a family
  • More stable career that is supportive of family leave, lactation, flexible work
  • More stable living conditions
  • More ability to accomplish other personal fulfilling life goals (e.g., travel, etc.)
  • More maturity and a better social support system

So what can you do?

Just as in other aspects of life, some risks stand as they are in pregnancy, while others can be mitigated with lifestyle factors and empowering information. 

Live a healthy lifestyle

Many of the risks around pregnancy at age 35+ are due to declining egg quality. While aging is inevitable, you can still take steps to support egg quality by living a healthy lifestyle - eating well, minimizing stress, exercising regularly, avoiding cigarettes, and limiting alcohol. Research shows that health does matter when it comes to pregnancy outcomes at all ages.

Specific nutrients to support egg quality include Omega-3 fatty acids, CoQ10, Vitamin D, Inositol, Zinc, Folate and antioxidants. 

It’s important to note that male factors aren’t as well understood around risks, but research has shown that these lifestyle factors matter for men too.

Reduce likelihood of other risks 

Similarly, many of the risks discussed around stillbirth relate to living a healthy lifestyle. These include managing weight/body mass index, blood pressure, diabetes, and avoiding smoking and alcohol use.

Empower yourself with information

There are certainly risks to pregnancy at 35+, but by empowering yourself with information, you can weigh these risks against the benefits of waiting, and you can also take steps to mitigate these risks with lifestyle factors and information that can help support your pregnancy and birth. The following have been shown to help support birth at 35+:

  • Find a supportive provider: finding the right provider is key to any pregnancy, but particularly at 35+, a supportive provider will be open and honest about your options for screening and testing and can help navigate options and concerns you may have
  • Be ready to advocate for yourself: this will be less necessary with a supportive provider, but know that based on hospital or insurance guidelines, you may feel pressured to opt into interventions like a scheduled C section. However, even at 35+, a planned elective C-section is significantly linked to higher risk of maternal death and severe complications compared to planned vaginal birth. In fact, the authors of one study on the effect of planned mode of delivery in women 35+ conclude that “when possible, planned cesarean deliveries should be avoided in this population.”
  • Understand induction: It’s important to know that a large study known as the 35/39 trial showed that induction in women 35+ shows no benefit or no risk at 39 weeks. However, another large scale trial that occured over five years did show a slight benefit and lower risk at 40 weeks (rather than waiting to 41 or 42 weeks to birth naturally or induce at that time. Consider these statistics when discussing your options with your provider.
  • Consider midwifery care: A large scale study in the UK from 2008-2010 showed that midwifery-led care was associated with fewer interventions and fewer C-sections with no increased risk to baby as compared to hospital obstetric labor and delivery settings, which saw more interventions and C-sections and more NICU admissions for women age 40+.

You Don’t Age Overnight

Remember, you don’t age overnight. Risks to a woman age 35+ are higher than for those less than age 35, but your risk increases gradually, and management of risk isn’t entirely out of your control.

The vast majority of women age 35+ who carry to term will birth a healthy baby. In addition, some risks can be somewhat managed by good care and good health. And remember, waiting comes with benefits too.

We appreciate as always the in-depth research compiled by Evidence Based Birth on this topic.

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Hillary Bennetts, Nutritionist

Hillary Bennetts is a nutritionist and business consultant focusing on prenatal and postpartum health. In addition to nutrition consulting, she provides business consulting and content creation for companies in the health and wellness industry. Hillary spent almost a decade in corporate consulting before shifting gears to combine her lifelong passion for health and wellness with her business background and nutrition education.