Where’s the evidence in what to expect when you’re expecting?
By Adrienne M. Roehrich
In pregnancy, there is a list a mile long of what you can not do. Not only are there warnings on cigarettes and alcohol, your great-aunt will tell you to microwave your ham or skip cold cuts altogether. A stranger on the street tells you not to carry your heavy purse or grocery bag, and at the very least may give you a dirty look for the coffee cup in your hands (never mind if it contains herbal tea with no sweetener.) Your doctor tells you how much weight to gain (or not to gain) and when. The pile of pregnancy books say no sushi, sing to your belly, and don’t go to the movies.
Associate professor of economics at the University of Chicago Booth School of Business Emily Oster began to wonder if there was any evidence for the old wives tales and exactly the evidence for the medical advice given to pregnant women when she became pregnant with her first child. Published in 2013, Expecting Better is the book resulting from her critical analysis. No stranger to writing, Oster’s work has appeared in The New York Times, The Wall Street Journal, Forbes, and Esquire.
Weighing in at over 300 pages, including bibliography and index, Expecting Better is chock-full of pregnancy myth and science information. Oster used her training and skills as an economist, a “decision science,” to determine what decisions are best during pregnancy. She points out that the point of a decision is taking the data and weighing the plus and minuses — something that can lead to different best outcomes of decisions for different people. Oster points out that in many things in life, decisions aren’t based only on data but also on the person’s feelings. And in pregnancy and pregnancy advice, there are a lot of feelings involved.
Oster expresses her dismay at the list of rules presented to the pregnant mom by the doctor, friends, colleagues, books, and strangers on the streets, many of which contradict each other. From her doctor, she expected to hear the data, the pluses and minuses and be able to be involved in the decision-making of her healthcare and her day-to-day life. This was not so. Your mileage may vary, but many pregnant women find themselves in just this exact situation.
For my first child 14 years ago (pictured in feature image), I was in that situation. My doctor dictated what I could and couldn’t do and I did my best to follow all the rules put forth by society. However, when I made requests or questioned some of the rules and was overruled by my doctor I didn’t stick around. I came to term and had my daughter with him because I was young and didn’t assert myself and had no idea who else to see. By the time I had my second child (in utero in feature image), I switched to a provider who was much more interested in having a conversation and allowing me to participate in the decision making of my own health care and life. It’s also important to note that the rules change over time. The rules from my second child nearly 13 years ago were much different than the rules put forth today — although those old rules persist as old wives tales, family advice, and societal pressure.
That changing and updating of data is key. Oster found that by tracking back to the source, from her doctor to the official recommendation from the American Congress of Obstetricians and Gynecologists to the most recent randomized trials and studies published, the actual recommendations (not rules, mind you) changed. Science is ever-updating and sometimes the doctors aren’t as quick to change their recommendations, let alone society.
The book is divided into five parts: Conception, The First Trimester, The Second Trimester, The Third Trimester, and Labor and Delivery. Depending on where you are at in your reproduction stage, you may want to read the introduction, then skip straight to your section. Or, if you are like me and have no plans for kids but thought the book sounded interesting (I love data-driven, evidence based health stuff), you can read from start to finish. The book is a story, not just the data (despite Oster’s claims that it is just the data). Depending on your time for reading and your need to know the information within the book, you could get through it pretty quickly. If you are reading for decision-making during pregnancy, then you may want to slow down a bit and read more carefully and take the time to think over the data to make your best decision.
Oster starts out her first chapter with the age question. How old is too old? Why? Yes, the number is fertility based – some of the recommendation from research from the 1800s and other from more recent, better controlled research. And she moves smoothly from that topic to that of weight and right into graphs of why pre-pregnancy weight is more important to consider than pregnancy weight using a couple graphs. (Yay, graphs!)
Starting about page eight, I noticed citations. I headed back to the Notes section to see exactly what Oster was citing, and it is along the lines of papers from the New England Journal of Medicine, Archives of Gynecology & Obstetrics, Reproductive Biology & Endocrinology, International Journal of Obesity & Related Metabolic Disorders, Reproduction, American Journal of Clinical Nutrition, and Early Human Development. These are peer-reviewed, often high impact factor (meaning the articles in them get cited a lot within their fields), and respected journals. In general, we can expect that the studies being published in them are rigorous and quality we can trust.
At the end of the chapter, Oster presents “The Bottom Line,” a summary in 1-2 sentence, bullet point form of the topics she covered and what the bottom line is. Of course, these bottom lines do not have data and are rather generalized – just like the advice that Oster found so frustrating. I was also a little wary of the bottom line at the end of the nausea chapter – rather than give a DIY nausea pill cocktail remedy, maybe this one should have read “see your doctor and trust their advice.”
In the Conception chapter, we get a primer on fertility and conception. I’m reminded of a recent story I heard where a study was looking at why people get pregnant unintentionally and found that a large percentage weren’t using birth control because they thought they couldn’t get pregnant. Basically this was their premise because they’d had unprotected sex and didn’t get pregnant so they figured they couldn’t (ie scare-tactic biology class ‘if you have sex, you will get pregnant’ totally back-fired). It seems many people need such a primer. Not only does she discuss when you might need to have sex to get pregnant, she also tackles how frequently to have sex. Guess what? It doesn’t matter. If you have sex once in the proper 5 day window or every day during the window, the calculated predicted chance of pregnancy was the same, according to one set of researchers. Getting pregnant is both harder and easier than all the advice and information says it is.
Not only do you get cited hard data (with graphs!), the book also gives history lessons, like the one in chapter 3 methods of determining if you are pregnant. This lends the book to easy read-ability. An interesting note to this chapter is the discussion of increased sensitivity in our technology. Pregnancy tests that are standardly used have increased sensitivity from the 1980s to today to the point that 22% of miscarriages resulting from unknown pregnancies in the 1980s would be known pregnancies today, giving us 22% higher miscarriage rates. I can see the headlines now – why do we miscarry so much more today? Well, we don’t, we just know we are pregnant that much sooner today.
Over 10% of Expecting Better is dedicated to the “Big Bads” of caffeine, alcohol, and tobacco. Depending on how much caffeine you go with since the recommendations from source to source (including doctors and national agencies) varies, you may even need to check with your barista about having that cup of java!
Concerned about miscarriage? Oster devotes a chapter to the actual contributions to risks of miscarriage – length of pregnancy, age, the “Big Bads,” nausea (or rather lack of), and vaginal bleeding to name a few. Want to know what foods you really should avoid? Oster goes into a summary and detail on that list you are given of what to avoid for why you are being told to avoid it (the risk associated).
During the book, Oster not only goes into the studies, but also discusses why some studies are more valid and relevant than others. Her teaching skills become evident as she describes concepts such as randomized trials in layman’s terms. She may undershoot her target audience’s understanding a little, and likely yours if you read this blog, but I’m always up for refreshers. She also goes into why these gold standard studies are not always available for these pregnancy studies. As our science ed editor Chris Gunter commented on the November 2 podcast, the governing body (IRB) would not approve randomized trials on pregnant women for ethical reasons.
Some topics may not apply for you in the first place. If I were to become pregnant at this time, I could completely ignore the “Beware the Deli Meats!” chapter since the only issue is unwashed vegetables and fruits can carry contamination and I wouldn’t consume those or any of the non-vegan items (everything else of concern) under normal circumstances anyway. However, reading this chapter may make you want to become vegan as you read just her summary, let alone if you choose to delve into literature yourself.
Reading the book, the conception primer is not the only biology primer. There are primers on alcohol and caffeine pathways in the body (go, biochemistry!), chromosomes, and more! Of course I learned stuff I didn’t know about pregnancy and health. I also learned stuff I would have thought I knew, such as the difference between chemical and clinical pregnancy.
In general, the hand-waving is minimal. There were a couple places where she used a little more feeling than evidence (especially the section about home birth), but mostly it was data driven. Except for her 1-liner bottom lines at the end of each chapter, Oster discusses which studies she choose to rely on and make decisions from and why. She tends to choose larger studies with data collected during the interested period (ie, during pregnancy) and with longer term checks on the resulting children. Recommendations that read “drink like a European adult, not like a fraternity brother” appeal to my sense of humor and enjoyment of the book but may be off-putting to some. One reservation I had was that some of the advice in the nausea chapter included a home cocktail for nausea treatment and something that seemed suspiciously like doctor-level advice. However, we are all adults reading this book, so whether or not such cocktails are made and advice is taken is up to said adult.
Oster stays away from what she clearly thinks is doctor territory most of the time. She does, however, make it clear that based upon her research of the medical literature, she believes some of the standard practices are either not based on evidence or at the least based on outdated evidence. I cringed when she cited some studies on acupuncture showing it worked for instigating childbirth. She also pointed out more recent (and probably better) studies shows it does not work, but her bottom line was “it might work.”
We also get Oster’s birth story. I’m of a split opinion on this. Personally, I love birth stories, but I’m not sure it fits into an evidence-based pregnancy book. On the other hand, it completely fits the tone of the book. She uses it to point out things you might want to prepare for. However, I had things I needed to consider and prepare for for both my children’s births that she didn’t cover. Her labor portion is not comprehensive.
My final recommendation is, this is a book to read if you are pregnant, thinking about getting pregnant, give advice to pregnant people, or have friends who are pregnant who talk about it. It isn’t light-hearted reading, there is some number-crunching science, but it is a good read and a fun read (if you are into that sort of thing, which I am, even long past child-bearing plans). And it is definitely a resource that you can use to argue against the random anecdotal data.
Feature image is of me when I was pregnant with my son in 2001. He was born 2 weeks after the photo was taken.