10 Fertility Myths: Fact or Fiction with Emily Oster
I’m so excited to welcome Emily Oster, renowned economist, bestselling author, and professor at Brown University. You probably know her from her popular books Expecting Better, Cribsheet, and The Family Firm. Today, Emily joins me to take on “10 Fertility Myths: Fact or Fiction,” and we’re diving into what the data really says (all while having a great time chatting about some of our favorite topics).
We’re breaking down some of the most common beliefs about fertility; things like alcohol and caffeine use, stress, age, male fertility, and when to see a specialist. Emily is known for her clear and evidence-based approach to decision-making, and I know you’re going to walk away from this conversation feeling more informed, supported, and empowered.
In this episode, we discuss 10 of the top myths around fertility, including:
- Whether alcohol and caffeine really impact fertility
- How timing sex and managing stress play into conception
- When it’s time to see a fertility specialist
- The truth about age-related fertility decline
- Common myths around male fertility and sperm quality
- How to use data in making fertility decisions
- Emily’s expansion of ParentData.org to support those who are trying to conceive
Dr Aimee: Welcome to the Egg Whisperer Show. We’re going to talk to the fabulous Emily Oster today. The title of today’s show is “10 Fertility Myths: Fact or Fiction with Emily Oster.”
How much of the conventional wisdom about fertility and pregnancy is actually backed by science? And what myths might be holding you back from making your best decisions for your journey? Emily Oster is an economist, bestselling author, and professor at Brown University, known for bringing data-driven insights to pregnancy, parenting, and fertility.
I’m a huge fan. I’ve been following her for a long time. I’m so excited to have her here. She is also the author of Expecting Better, Crib Sheet, The Family Firm and The Unexpected, each offering practical guidance, based on rigorous research. Emily is also the creator of parentdata.org, a popular platform that helps readers make informed decisions with clarity and confidence.
I highly recommend that you subscribe so you can get the insights that I get in my inbox as well. The site recently launched a new section dedicated to those trying to conceive. You’re my people. So go over to parentdata.org, expanding its evidence-based support to the fertility journey. Emily, can you tell us about the start of ParentData what your mission was there?
Emily Oster: Hey, first, thank you so much for having me. I’m so delighted to be here. I’m such a big fan.
So, the goal with ParentData is really to give people solid evidence-based information that they can use to make their own best decisions. The sort of connecting thread through all of my work, my books and ParentData, is really this idea that we are all going to make our own best choices if we have the evidence to do that with, not that the data is going to tell us what to do, but that underlying good choices is understanding what my options are, understanding what’s information and what’s misinformation. And so, when people come to ParentData, I want them to trust that they can ask a question, that they can get an answer, and they can trust the answer. They can know that it’s based on evidence, whether it’s infertility or pregnancy or parenting.
Dr Aimee: That’s great. And fertility comes with a lot of conflicting advice. I love being a fertility myth buster myself, and I rely on a lot of the things that you share when I try and educate my patients too. So, I want to go through some of the myths that you bust, things that I think a lot of people may not know.
So, can we go through some of those?
Emily Oster: Yes, absolutely. I’d be delighted.
Dr Aimee: So, the first myth is you must completely give up on alcohol when trying to conceive. My question here is that you’ve written that occasional alcohol in pregnancy isn’t as risky as many believe. However, what does the data say about drinking during the two week wait or while trying to conceive?
Emily Oster: So, drinking during the two-week wait is a little bit of an all or nothing thing. So, if you drink a lot, such as binge drinking, very heavy alcohol consumption during that period, that can interfere with your chance to conceive because if you drink a lot at the wrong time, it can cause an embryo of fertilized egg to not develop. However, drinking smaller amounts doesn’t have that impact, and with the timing there, it would not have an impact on the fetus ultimately. So, what I would tell people is, if you want to have a glass of wine, a couple glasses of wine, during that two week wait, there’s really no evidence to suggest that it would be problematic for conception.
This isn’t a good time for, you know, seven drinks at a time, although there’s never a good time for seven drinks at a time.
Dr Aimee: That’s right. Maybe on your 21st birthday and you might regret it for the rest of your life. Yeah.
Emily Oster: That will be the only time. If you do
Dr Aimee: I mean there’s so much shame that goes into being a fertility patient. You know, we shame ourselves and we think that somehow, we did something that caused us not to get pregnant. The first thing people think is like, it’s something I ate or something I drank, and it’s almost never that.
Okay, so the next myth is “caffeine will hurt your chances of getting pregnant.” And I’m saying that as I’m drinking my coffee. You know, many people trying to conceive are told to cut out coffee entirely. What does the research say about caffeine and infertility?
Emily Oster: The research does not support a link between caffeine consumption and infertility, and unlike some other things, there is really no mechanistic reason to think caffeine would interfere with fertility. There’s just no reason to think that would happen. In fact, moderate caffeine consumption during pregnancy is also completely fine.
And so, this is, it’s interesting. This isn’t a class of things that I think is very important to say because when people are struggling, when it’s taking longer than you expected it to, it’s very common for people to come and blame themselves and say, you know, “What did I do? What am I doing wrong?”
And when we suggest, “Well, maybe it’s coffee, maybe it’s that glass of wine, maybe it’s those potato chips you ate.” We end up with people saying, “I’m going to restrict and restrict and restrict,” and if those things don’t, there’s no reason to do it. And it just makes an already challenging situation worse.
Dr Aimee: Yeah,
Emily Oster: Now you’re not caffeinated.
Dr Aimee: Caffeine can help with your mood. You know, especially when you’re taking fertility drugs, you’re hormonal. You’re maybe feeling that estrogen fog, taking caffeine away from those patients… that’s not a good time to do it.
Emily Oster: It’s mean.
Dr Aimee: Okay. Let’s talk about sex. So, I get these questions all the time, and this is one of the myths that you must time sex exactly right, and that is everything. And there’s so much pressure on getting the timing of intercourse perfect. What is the data on how much room is there for error when it comes to timing sex?
Emily Oster: You want to be having sex on the day of ovulation or the day before. Those are the two days that you are most likely to conceive. You can conceive with sex a few days before ovulation, perhaps as much as six days before, although the chances are highest on one of those two days, but it’s not a 45-minute window.
I’m always thinking about that episode of Sex in the City where Charlotte is trying to get pregnant and she’s running around at a house party with this idea that it’s “our hour.” It’s not your hour. It’s a good idea to try to aim for the day of ovulation or the day before that gives you the highest chance, but it’s a two-day window at least.
Dr Aimee: Sex. Sex should not feel like an emergency.
Emily Oster: That should not feel like an, sometimes it feels like an emergency, but only in a good way.
Dr Aimee: Let’s talk about stress now. You know, one of the first questions I ask a patient is, why do you think you’re struggling? What do you think your fertility diagnosis is? Because I think it’s important to listen to patients. Oftentimes they go unheard. One of the most common things people tell me is, I think it’s because I’m too stressed.
Stress gets blamed for a lot of fertility struggles. How strong is the evidence linking stress and trying to conceive outcomes?
Emily Oster: There is some evidence suggesting small impacts on conception from extreme stress. But the effect sizes in these studies are not very big. I also think it’s, in that case, important to focus on, what can you do?
People say, well just relax. This is a very stressful experience and that may be impossible. And so, I think in that case, you know, telling people, “Yeah, this is a stressful experience. And if there’s something that you find helpful in managing your stress, is it massage? Is it meditation? Walking outside in the forest?
Try to prioritize space for that because that will make you feel better,” rather than saying, “You have to relax because that’s how you’re going to get pregnant,” which I don’t think would cause anyone on the planet Earth to become more relaxed.
Dr Aimee: That is true. And the thing about stress, when I talk to patients about it, I say, “Okay, you’re stressed, but are you so stressed that you’re not sleeping, you’re not eating, you’re having panic attacks?” Like that’s the level of stress that I think would potentially cause problems with ovulation and fertility.
But most patients just feel stress, but it’s a healthy amount of stress because it gets them to pick up the phone and call me and come into my office.
Emily Oster: I think that many of these studies that focus on stress, the kinds of things you’re looking at are stressful life events. You know, the death of a parent, something which is, is pushing stress beyond what we would be experiencing in our normal, you know, “my job is stressful.” “ I’m worried about my pregnancy” levels of stress.
Dr Aimee: Okay. Next myth. You need to see a fertility specialist after just a few months of trying. So, my question is, how long should someone try before seeking help? What’s the data backed guidance for when to see a fertility doctor?
Emily Oster: There are some standard recommendations, which people are given: about waiting a year if you’re under a certain age, waiting six months if you’re over a certain age, seeing somebody immediately when you’re over 40. I don’t find those very helpful, nor are they especially well backed up by data.
You know, the idea of waiting a shorter time as you’re older has some logic because you know, you have fewer months of potential fertility too, to continue. But I, I think there isn’t an answer to this question where you could say it’s two months for this age, it’s three months for this age.
And I think it also should depend a little bit on how hard you’re trying. You know, there is a difference between, “for the last year I haven’t been on birth control and we’ve sort of just been having sex whenever,” versus “for the last year I’ve been tracking my ovulation every month and we’ve had sex on one of the two, you know, maximal ovulation days and we’ve done all these other things.”
Then, you know, you’ve learned quite a lot more. So, I, I think as with many things in this space, you don’t want to be hemmed in by the guidelines. This is something worth talking with your doctor about. Maybe even before you start to conceive, you know, what is the point at which I should come in if it hasn’t worked out.
Dr Aimee: And even just getting a fertility check-in, just like you said, talk to your doctor before trying, you know, we don’t take a cross-country trip in a car without getting the car checked and looking under the hood. So, pregnancy should be the same thing. You know, get an ultrasound, do some blood work, make sure that there’s nothing that’s going to get in the way so you don’t feel like you would have regret if you waited longer before seeing a fertility doctor if you’re worried.
Okay, myth number six. Every cycle is a 28-day cycle with ovulation on day 14. Clearly a myth. So many fertility apps are based on this textbook cycle. What does the actual data show about ovulation timing and cycle variability?
Emily Oster: There’s a lot of it. Normal cycles can be between 21 and 35 days. Even if you’re having a regular cycle, people have cycles that differ in their length. You can have differences in the timing of ovulation within the cycle. So, you know, most people have, it’s more consistent that you’d have about a 14-day phase in the second half of the cycle and there might be a longer or shorter time at the beginning that’s also not consistent. People can have a 10-day phase or an 11-day phase.
So, if you are a consistent menstruater with really consistent cycle tracking, you probably have some sense of this. If you’re going into it and you’re saying, “Well, I don’t know anything about my cycle, but let’s just assume it’s exactly 28 days every month, and I ovulate on day 14.”
That isn’t all the information that you need. There are more investments you should make in trying to figure out how your cycle’s working if you want to maximize your chances of conception.
Dr Aimee: I wish I was a brand ambassador for the Aura ring. I love my Aura. It tells me exactly when to stay away from my husband, exactly when to tell him to put his bulletproof vest on every month. It’s very reliable.
Emily Oster: Yes.
Dr Aimee: Okay, the next myth is fertility starts declining sharply at the age of 30. I mean, I get so many calls, “I’m turning 30 next month,” or “I want to have a baby by 35,” and people are panicking.
I’m like, “Where’s this coming from?” Clearly a myth. So, can you walk us through what the data really says about age related fertility decline?
Emily Oster: There’s a glass half full, glass half empty part of this, which is your fertility is pretty much declining as you age, starting in your teens. And it is true that age is an important determinant of fertility, but I think we give people this impression that there are these sharp changes. And that’s not really, not how biology works.
It’s not a space where you step off the cliff at 30 or step off the cliff at 35 or even step off the cliff at 40. As you age it becomes more difficult to get pregnant. But people absolutely do get pregnant at 35, at 36, at 37, at 40.
I feel like with age you want to simultaneously hold the sort of “two things are true.” One is that you know, your age is a determinant of fertility and something you should think about, and it is not the only determinant of fertility. And certainly, it’s not the case that if you wait another two months and now, you’re 30 and one month rather than 29 and 11 months, that somehow everything has collapsed and changed.
Dr Aimee: Right. No one’s pushing you off the egg cliff at 30 or 35 or anything like that.
Emily Oster: Even though we have special names for the over 35, which I think makes it worse, like geriatric pregnancy,
Dr Aimee: That’s so mean. It’s so mean.
Emily Oster: Advanced maternal age, it’s, it’s great.
Dr Aimee: So cruel. I try to use words, so they don’t internalize the terms that they see, you know, when they go to the doctor on their charts. So, I say, it’s advanced mitochondrial egg age because it’s about the eggs.
It’s not like you as a person, it’s not you. Our eggs are the fastest aging cell in our body. It just happens to be in your ovary. That might be aging a little faster, but you are certainly a young, healthy, very fertile woman.
So the next myth is male fertility doesn’t decline with age, which is so not true. And you’ve noted that semen parameters decline with age but have little impact on reproductive success. How should this influence couples planning when trying to conceive?
Emily Oster: So, it is true that men can have babies for longer. Their fertility also declines with age. A piece of advice that people should be getting is that when they are checking on fertility, before they start to try, you should also check him if there is a male partner. And I don’t think many people do that, because we often don’t think about male infertility as a sort of bigger piece of this, but it’s about half of infertility, people think, is male factor infertility.
And the reason it’s a great thing to check is because a lot of the things that can interfere with male fertility are changeable in the moment. So, unlike your eggs, which you get at the beginning and you’re using the whole time, men are making sperm all the time.
And so, things like heavy drinking, marijuana use, having your testicles be really hot, these can all impact sperm quality. And they’re fixable. It would be a shame to wait nine months and then find out that like all that extensive exercise, biking in tight shorts is the reason that you haven’t yet gotten pregnant.
Because you could have fixed that at the very beginning.
Dr Aimee: Totally. Now I add, because a lot of guys are into longevity stuff, they’re doing saunas, but they’re also doing ice baths. So, I’ve now recently added, don’t freeze your balls too. I say don’t cook ’em and then also don’t freeze them because people are getting into ice baths now and doing all that cryogenic stuff, you know, for muscle recovery.
Emily Oster: Keep your balls at a regular temperature. Is it so hard?
Dr Aimee: Is it so hard?
Dr Aimee: I know. Seriously. Okay, next thing. Wearing tight underwear has no effect on sperm count. That is a myth. So, given the evidence on tight underwear affecting sperm quality, what practical advice would you offer to men aiming to optimize fertility? And you can talk about underwear if you want.
Emily Oster: There are, my sort of favorite experiment in this is when they had a set of men wear extremely tight underwear all the time for weeks, and they got their sperm count more or less to zero. So, you, they get all the way down by, I mean, these, these were not like a regular pair of tight whities.
Dr Aimee: They were like corsets. They were.
Emily Oster: They were like
Dr Aimee: corsets for their balls.
Emily Oster: Testicle — balls.
Emily Oster: Ball corsets. If you want to keep your balls at a better temperature, wear some loose underwear. I think the bigger thing than this sort of underwear is things like saunas and then things like extended periods of time in bicycle shorts, like people who do a lot of cycling spending many hours a day on a bike. That is not true of many people, but it is also not good for your sperm count.
So just a little bit of thought. About this and it can go a long way.
Dr Aimee: Great. Okay, last myth. A normal semen analysis guarantees male fertility. So, my question is, considering that the semen analysis doesn’t tell the whole story, what else should be considered when assessing male fertility?
Emily Oster: There are a lot of different ways to do a semen analysis. There’s sperm count, there’s sperm morphology. You could do many versions of that test and try to get a better sense. It’s still not going to tell you everything in part because we have male factor infertility, female factor infertility, and then combined infertility.
And you aren’t going to get things from a semen test about translocations in genetic code and things like that. They could also be part of the fertility story. So, the semen is, is a piece of it. It’s not going to be everything. Just like doing an ultrasound and seeing that you’re ovulating, or that your ovaries are looking like they should, that’s not going to tell you everything either.
Dr Aimee: I have a checklist for every case that I do, and the checklist for the guys includes chromosome testing, carrier screening, sperm DNA fragmentation testing if needed. Y chromosome micro deletion testing if needed. So, I couldn’t agree more. So, let’s go back to ParentData’s core promises.
It’s to reduce anxiety by offering clarity, and your platform is. I always just trust what you say. It’s just a trusted place that patients can go to, that I can go. How can fertility patients arm themselves with data that helps them on their journey?
Emily Oster: I think of the fertility space here, and this is how we try to structure things at ParentData, is really having at least two phases. I think for a lot of people, they start their fertility journey thinking, “Okay, I, I haven’t been trying and now I’m going to start trying.” And I think that’s a really good moment for people to learn a lot.
Unfortunately, our education, our educational system has not always provided us with all the information about even how our menstrual cycle works. So, this is a moment to learn how my cycle works. How can I do some cycle tracking? Let me do some potentially basic testing about my fertility, basic testing, and my partner.
So, you know, we have a whole bunch of content that’s really in this space of just like “I am here to learn everything about the first stage of this.” And then of course my hope always is that people, that’s all that people will read in that, in that area, and then they will move on to the content of that pregnancy.
But there’s another phase if you are struggling with if things haven’t worked as quickly as people hope. Then I think there’s another place where it’s really valuable for people to be able to learn at least a high level overview about what are the options that I’m likely to be faced with if I’m pursuing fertility treatment, what’s the difference between IUI and IVF? Who might these things be right for?
Because I think often people come into fertility treatments almost blind. And then there is so much information all at once and you’re seeing the doctor and you’re trying to learn the basics while you ask them questions about your specific case.
And I just like much of pregnancy and parenting content, our goal is to give people enough information that they can come up with the questions that are really right for them. This is not replacing fertility doctors, obviously, but it hopefully gets people to a point where they say, “I understand what my options are, now I can engage with what is the right option for me.”
Dr Aimee: Excellent. Yeah, I mean, along the lines of people not understanding their menstrual cycles, so many people just don’t know that every cycle you make cyst. Then an egg comes out and it’s an ovulation cyst, and when I show it to people on ultrasound, I always, always have to qualify, “I see your cyst of ovulation and all of a sudden they’re like, “ Do I have cancer?”
I’m like, “No. You make a cyst every time you ovulate, it becomes a corpus luteum,” and it’s like that’s just one thing that everyone should know. Right.
Emily Oster: Yeah. I mean, I feel like there should be more education about this in sex ed. People should come out of high school knowing this information that they don’t,
Dr Aimee: Like these are the phases of the menstrual cycle, you know? Okay. So as ParentData grows, how do you envision expanding the “trying to conceive” section to support an even more diverse and inclusive community of people trying to conceive?
Emily Oster: It’s a very large collection of information designed for people who are building their families in non-traditional ways. Whether that’s with two partners who both have a uterus, whether it’s two partners, neither of whom has a uterus, whether it’s one person, whether its people thinking about surrogacy or adoption, and there are a lot of medical questions in that space. But there’s a lot of also just general decision making about, you know, if we’re going to have a sperm donor, do we want a known donor, an unknown donor? We have a, a really amazing writer, who is a midwife and they put together this large just set of content that again, someone could go very deep in and say, “Okay, now I really have a sense of what my choices are in this space.” Because, you know, not everyone is trying to build a family in quite the same way.
Dr Aimee: Right. Oh, that’s so great. Emily, thank you for joining me today. I am so happy and extremely honored that you took time to be here. I’m a huge fan, as I’ve mentioned many, many times. Do you have anything else that you’d like to add?
Emily Oster: I’m so delighted that you had me here and it’s a treat to get to talk and I’m so glad to get this information out to people because it feels, I think, so important to both of us.
Dr Aimee: Yeah. Remind us again where people can find you and ParentData and sign up for the “Trying to Conceive” newsletter.
Emily Oster: You can find us at parentdata.org and there’s a Trying to Conceive section on the website. You can sign up for a free trial of the newsletter, and you can find me on Instagram at Prof Emily Oster.
Dr Aimee: Awesome. Well, thank you again, Emily. Have a lovely rest of your day, thanks for all the incredible work. It’s super spectacular all the work that you do.
Emily Oster: Thank you.
Originally published at https://www.draimee.org.
