Expecting Better: Why the Conventional Pregnancy Wisdom Is Wrong—and What You Really Need to Know

Award-winning economist discovers that most pregnancy rules are often misguided and some are just flat-out wrong.

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Karsen: From the Parents Club, I’m Karsen Kolnicki. This is your briefing.


Karsen: Today, we’re discussing Expecting Better: Why the Conventional Pregnancy Wisdom is Wrong—and What You Really Need to Know. Written by Emily Oster.

In this title, when award-winning economist Emily Oster was a mom-to-be herself, she evaluated the data behind the accepted rules of pregnancy and discovered that most are often misguided and some are just flat-out wrong.

Karsen: Vincent Phamvan on the key takeaways [pause] and what you need to know.


Karsen: Vincent, there’s a pretty widely accepted list of rules for parents during pregnancy. These are things like don’t drink alcohol and avoid eating sushi. Which of these are true and which are myths?

Vincent: That’s exactly what Emily Oster tackles in this book. When she was pregnant, she decided to evaluate the data, which of course comes from her background as an economist. In doing so, she discovered that more often than not, these rules were either misguided or wrong.

It definitely makes for a very interesting read.

Karsen: It sounds like the author was pretty skeptical of the traditional recommendations like that pregnant women should quit drinking coffee entirely. How did she approach her personal decision-making?

Vincent: Well, Oster’s background uses the economist’s framework for decision making. First, she made sure that she had good data, starting with academic medical literature that these recommendations were based on.

The second part of the economist’s framework takes a look at the costs and benefits of a decision. Different people have different preferences, but it’s helpful to have a clear idea of a decision’s cost and what the benefits might be. Then, parents can make smart decisions instead of blindly following recommendations.

Karsen: So the pregnancy journey starts with getting pregnant. What does the author say about this? For example, tribal knowledge says that a woman’s eggs are best used by age 35.

Vincent: Yes, Oster argues that this is not entirely true. She found that fertility does decline with age, especially after age 40. However, in a study of 2,000 women trying to conceive, 36 percent of those over 40 got pregnant within a year.

Karsen: What’s the most important factor when it comes to conception?

Vincent: Well, one important factor is timing. You can get pregnant up to five days prior to ovulation, but it’s easiest to conceive either while you’re ovulating or a day before.

Karsen: How can a woman check to see if she’s ovulating?

Vincent: There are three ways for figuring out when a woman is ovulating—temperature charting, testing cervical mucus, and the third one… well, the author calls them pee sticks.

The pee sticks are the most accurate, but they’re costly—about $40 per month.

Karsen: And temperature charting is free, right?

Vincent: Yes, temperature charting is pretty simple. You just take your temperature every day at the same time. There are lots of mobile apps you can use too, but for the two weeks after ovulation, your body temperature will be higher than normal.

Oster says that in a University of Naples study from the 1990’s, sixty percent of women who participated were able to pinpoint either the day of or the day before ovulation using temperature charting.

Karsen: And the last method is cervical mucus. How accurate is this?

Vincent: The author says that this is almost 50 percent accurate at detecting the day of ovulation.

Karsen: If it takes two weeks to know if you’re pregnant or not, should you avoid alcohol during that time period?

Vincent: The author says no. During fertilization, she says that light alcohol consumption won’t do serious damage. Even heavy drinking can kill the cells developing into your baby, but other cells will replace them.

If you drink too heavily and kill too many cells though, the embryo won’t develop and you won’t become pregnant at all.

Karsen: So, overall a glass of wine here and there is fine.

Vincent: According to Oster, the answer is yes.

Karsen: Good to know. Okay, so once a woman becomes pregnant, what do the parents need to know during the first trimester? I assume that the biggest concern is a miscarriage, so it’s best to avoid alcohol, coffee, and sushi.

Vincent: Surprisingly, the author argues that one or two drinks per week during the first trimester won’t negatively impact your baby’s IQ or behavior, and also it won’t increase the likelihood of miscarriage. For caffeine, the evidence says two 8-ounce cups of coffee a day won’t harm a baby.

The author says that when it comes to food, she wouldn’t worry much about raw eggs and raw fish. However, it’s best to avoid other raw meat, make sure you wash fruits and vegetables, and avoid gardening or handling cat litter.

Karsen: What about the mercury content in fish? Isn’t that a concern?

Vincent: Yes, there is a concern with mercury content affecting your child’s IQ, but fish is also rich in omega-3 fatty acids, which can boost your child’s IQ. My wife, Erin, completely avoided swordfish while she was pregnant, which has one of the highest mercury levels.

But Salmon on the other hand, high in omega-3 fatty acids which is good… and also relatively low in mercury content. Sardines are great too. And avoid canned tuna.

Karsen: Got it. When do most parents choose to share their pregnancy announcements with family and friends?

Vincent: Most people wait until the 12th week to share the pregnancy news for fear of miscarriage, but there’s not a sudden safe period. The chances of miscarriage gradually decline throughout pregnancy. 11% chance of miscarriage at 6 weeks, 6% chance at 8 weeks, and 2% chance at 11 weeks.

Karsen: What does a good, healthy first trimester look like?

Vincent: One sign of a healthy pregnancy actually is nausea. The data shows that 30% of women who had first trimester miscarriages didn’t experience nausea. Most are nauseated between 6 and 14 weeks, vomiting only for a few days. There are also safe treatment options like taking ginger or vitamin B6 to anti-nausea drugs like Unisom or a stronger prescription drug like Zofran.

Karsen: Later on in the pregnancy, I’ve heard about prenatal tests. Does the author say anything about this?

Vincent: Yea, so prenatal testing can detect chromosomal abnormalities like Down syndrome. There are two testing methods: prenatal screening and invasive testing.

For prenatal screening, it’s not always 100% accurate. It’s possible to get a false negative where everything looks good, but it’s not. The opposite is also true where you can get a false positive, where the test shows irregularities, but everything is okay.

Karsen: How is prenatal screening done?

Vincent: Oster describes it as being a combination of blood tests to check hormone levels along with an ultrasound. There’s also a newer method that’s slightly more accurate by analyzing free-cell DNA. That uses a small amount of the mother’s blood to analyze. The risk of an incorrect negative test is one in 90 thousand women aged 30-34.

Karsen: So is invasive testing more accurate than both of these?

Vincent: Invasive testing is 100% accurate, but carries a small risk of miscarrage—one in 800. Invasive testing takes a sample of the baby’s cell from the amniotic sac between the 16th and 20th week of pregnancy.

There’s also another procedure called a CVS where a sample is taken from the uterus between 10 and 12 weeks.

Karsen: Or, the other option is to avoid medical intervention completely.

Vincent: Right, another option is to just wait until the baby is born, since the statistical chance of chromosomal abnormalities is low.

Karsen: Moving onto the second trimester, parents are faced with a few decisions. When can you find out the sex of a baby?

Vincent: Typically by 20 weeks, you can find out with ultrasound or invasive testing. There is another test that determines sex with a blood sample. That can be done anytime, but it’s not 100% accurate.

Karsen: What else should parents know in the second trimester?

Vincent: Oster does talk a bit about exercise. The main takeaway is that women who exercise have lower-risk pregnancies, but it also could be that these women were just healthier to begin with. Prenatal yoga could have positive effects, but the data set is pretty small.

One note though is to avoid sports where you might fall… like skiing and snowboarding. A fall could cause the baby’s placenta to detach, which would not be good.

Karsen: How about sleep for the mom?

Vincent: Oh yea, that’s a good area to discuss. The author says that sleep aids can be helpful in moderation and there are a few safe options. She mentions Unisom as one of them. Using Ambien is safe, but a Taiwanese study showed that long-term Ambien prescriptions while pregnant could cause low-birth-weight babies.

Karsen: Sounds like moderation is the key there.

Vincent: Yes, definitely. Lastly, on sleep, women are often told not to sleep on their backs because of reduced blood flow to the baby, but the majority of evidence suggests that this is impractical.

Karsen: In the third trimester, you’re on the final stretch. How can moms and parents avoid a premature birth?

Vincent: Well the good news from Oster is that premature birth isn’t as big of a risk as it used to be due to advances in technology. Babies born up to 22 weeks early have a chance of surviving.

The author also shares that if you go into labor early, the doctor can delay birth by a few days with drugs. That gives mothers time to get steroid treatments that speed up fetal lung development.

Karsen: How can you get an estimate on when your baby is coming?

Vincent: Yes, the author talked about how cervical checks can predict the timeline of labor. So your doctor can tell you how dilated your cervix is. Right before labor, it opens up to 10 centimeters. So that can help… but even better is cervical length, which is called effacement.

Effacement has more predictive power according to the research.

Karsen: I know that some people schedule labor inductions. Is there any data about the safety of doing so?

Vincent: So the author mentioned that labor inductions and cesarean sections have become more common in the United States because of convenience. Although C-section is good in an emergency, Oster says that it shouldn’t be your first choice.

She also says that the data shows that induction is safe at full term. If done earlier, it has some risk. There was data that showed that nipple stimulation is a safe, at-home method of induction that had proven effective.

Membrane stripping was another one that showed effectiveness. That’s when a doctor or midwife uses a gloved finger to separate the amniotic sac from the wall of the uterus at the cervix.

Karsen: During labor, what should parents know?

Vincent: The author shared that in a 2002 study of 1,300 women in Hawaii, that the average speed the cervix dilates is 1 to 2 centimeters per hour.

There’s a few phases of labor. The first stage includes dilation and active labor. On TV, you see that a woman’s water breaks and then she goes into labor right away, but this is only 10 percent of women’s experiences.

Karsen: What about the second stage of labor?

Vincent: The second stage is pushing, which can be anywhere from a few minutes or a few hours. A common labor problem the author shares is trouble pushing the baby out, often because of the baby’s position.

Two situations that may result in a C-section. The first is if you’ve had a C-section before, the studies show that there’s an increased risk with vaginal birth after cesarean.

The second is breech, where a baby is positioned to come out feet first. In about half of breech cases, the doctor or midwife can move the baby manually by pushing from the other side.

After the baby comes out, the third stage is placenta delivery, where the placenta is removed after the baby. This is usually painful, but quick.

Karsen: And the umbilical cord?

Vincent: Right, so after labor, some mothers may decide to delay the clamping of the umbilical cord. It’s a way to get extra blood to preterm babies, who are at risk of anemia and other complications. We did this when my daughter Lily was born.

And for dads, you have a decision to make whether you want to be the one to cut the umbilical cord. I got to do this when Lily was born. You cut the umbilical cord between the two clamps.

Karsen: It sounds like each birth is pretty unique.

Vincent: Yes, that’s why the author recommends putting together a birth plan. That way you can write down your decisions in advance and discuss them with the doctor or midwife.

You’ll want to know about things like eating and drinking in the delivery room. Although it’s not dangerous to do so, some doctors don’t allow it.

You can also include decisions like hiring a doula, which is a childbirth specialist that advocates for the mother. Randomized trials have suggested that doulas have a significant impact on birth outcomes: women with doulas are half as likely to have a C-section, less likely to use an epidural, and have shorter labor.

Karsen: It sounds like the key takeaway from this book is that every decision has pros and cons, so it’s best to have all the facts that you can. Some things aren’t as dangerous as conventional wisdom makes you believe, while other standard practices are actually quite dangerous. It’s good to understand that not all scientific research is high-quality, so it’s important to know the difference, especially when it comes to correlation and causation.


Karsen: That’s it for your briefing. I’m Karsen Kolnicki. See you next time.


Pregnancy—unquestionably one of the most pro­found, meaningful experiences of adulthood—can reduce otherwise intelligent parents to, well, babies. Pregnant women are told to avoid cold cuts, sushi, alcohol, and coffee without ever being told why these are forbidden. Rules for prenatal testing are similarly unexplained. Moms-to-be desperately want a resource that empowers them to make their own right choices.

When award-winning economist Emily Oster was a mom-to-be herself, she evaluated the data behind the accepted rules of pregnancy, and discovered that most are often misguided and some are just flat-out wrong. Debunking myths and explaining everything from the real effects of caffeine to the surprising dangers of gardening, Expecting Better is the book for every pregnant woman who wants to enjoy a healthy and relaxed pregnancy—and the occasional glass of wine.

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