Expecting Better contains a wealth of information on conception, pregnancy, and labor. Here are some of the most memorable points, especially when they contradict common wisdom.
Your chances of getting pregnant decline with age. Chance of conception in a month is 24% at age 25; 21% at age 30; 16% at age 35; 7% at age 40; and 3% at age 45.
In terms of timing sex, it’s pretty much impossible to get pregnant outside of a 6-day window before the day of ovulation. That’s because the egg only survives for 24 hours after release, so the sperm have to be waiting in the Fallopian tube to greet the egg. Luckily, sperm live up to 5 days. Therefore, the best chance of conception happens the day before or the day of ovulation. Conception can still happen up to 5 days before ovulation, with lower chances.
The frequency of sex during this 6-day window does NOT make a difference in chance of conception - it's more important to hit the right day.
There are a variety of ways to track ovulation, including temperature charting and cervical mucus. The most accurate is ovulation sticks, which detect hormones in urine. Of women randomly given access to ovulation detection sticks, 23% got pregnant within 2 months, vs 15% who didn’t have them.
Alcohol: There’s no strong evidence showing 1 drink per day affects child IQ, test scores, or behavior problems. However, this means sipping 1 drink per day, not binge drinking 7 drinks in one night and abstaining the other 6 nights.
Caffeine: It seems safe to have up to 3-4 cups of coffee per day.
Tobacco: Tobacco is not recommended at any time in pregnancy or in life.
Food: Toxoplasmosis and Listeria are the most dangerous infections to the baby. These come from undercooked meats, unwashed produce, and other sporadic outbreaks. Otherwise, for typical foods that may cause illness (from raw eggs, raw fish, shellfish) use your standard caution - your risk of infection aren’t higher when you’re pregnant.
Pharmaceuticals: Many drugs that are...
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Emily Oster is a Harvard-trained economist at Brown University. When she was pregnant, she was dismayed at the quality of pregnancy information. First, clinicians and other mothers seemed to have contradictory ironclad rules for pregnancy. Secondly, and even worse, it wasn’t clear what evidence supported their beliefs, despite their strength of conviction!
For Oster, getting pregnancy advice felt like having a realtor who said that some people don’t like houses with backyards, so they wouldn’t have any houses with...
Contrary to what you learned in high school health class, it’s not that easy to get pregnant. Female fertility peaks in your teens, then decreases gradually from then on, until falling off a cliff around age 45.
In more positive terms, you’re much more likely than not to have a baby if you’re in your 30s.
A study of births at different ages from the 1800s shows that the chance of having children:
A more modern study of artificial insemination showed that after 12 cycles (months), women under 30 had a pregnancy rate of 75%; women age 31-35, 62%; women over 35, 54%.
(Shortform note: it’s not explained what comprises the 46% of women over 35 who weren’t able to get pregnant after 12 cycles. What fraction of women will get pregnant with more cycles, and what fraction will unfortunately never be able to conceive?)
70% of the US is overweight (BMI > 25) and 35% are obese (BMI > 30).
Obese women are less likely to get pregnant and more...
Congratulations, you’re pregnant! It might have been a journey to get here, but there are still 9 months of things that people worry about.
Pregnancy is usually tracked in terms of weeks (e.g. “I’m 28 weeks in.”) Weeks in pregnancy are counted from the time of your last period. So 5 weeks into pregnancy is 1 week past your missed period.
The first thing we’ll discuss is common vices that people generally advise to stop during pregnancy - caffeine, alcohol, and tobacco.
There’s a lot of stigma and confusion around the use of substances in pregnancy. In perhaps the most provocative part of Expecting Better, Oster argues that caffeine and alcohol, in moderation, show no evidence of being harmful to the child.
To cut to the chase:
Where does all the confusion around...
A minority of pregnancies end in miscarriage, and there’s largely nothing you can do about it. 90% of miscarriages in the first trimester are due to chromosomal problems at conception.
Here’s the risk of miscarriage by week:
|Week||Chance of miscarriage|
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Pregnant women are commonly recommended to avoid a long list of foods - raw eggs, raw fish, cheeses, deli meats, to name a few. The general fear is that food illnesses can bear a risk to the fetus.
Oster argues that many food illnesses are actually no riskier than when you’re not pregnant. But two forms are, and are worth avoiding.
Typical food poisoning is caused by Salmonella, E.coli, and Campylobacter. These pathogens cause diarrhea, nausea, and vomiting, but do not usually affect the fetus.
For foods more at risk of harboring these bacteria, like raw eggs, raw fish, and shellfish, use your standard caution. Chances are you haven’t gotten food poisoning more than once a year, and this isn’t going to get more likely when you’re pregnant.
Oster acknowledges two illnesses that are harmful:
Toxoplasmosis affects 1 in 1,500 babies and causes mental retardation, blindness, and epilepsy. Acute...
Nausea is very common in pregnancy - 90% of women report nausea, and >50% report vomiting. The important thing concerning nausea is to know when you have an unusually high level of nausea, and when to seek help.
Here’s what normal nausea looks like:
The primary purpose of prenatal screening is to detect chromosomal abnormalities, the most common being Down Syndrome, or trisomy 21. Tests also screen for the rarer Edwards syndrome (trisomy 18) and Patau syndrome (trisomy 13), both more severe than Down Syndrome with babies rarely surviving their first year. Families at high risk for genetic disorders may also screen.
The risk of Down Syndrome increases with maternal age, from 1 in 1488 from ages 20-24, to 1 in 746 in ages 30-34, to 1 in 30 for age 45 (a fuller chart is shown later). For some comparison, the risk of a car accident in the next year is 1 in 50, and the risk of being audited in the next year is 1 in 200.
There are largely two types of screening: non-invasive (cell-free fetal DNA, ultrasound), and invasive (amniocentesis, chorionic villus sampling). Non-invasive tests pose no risk to the fetus but are more prone to false positives and false negatives. In contrast, invasive tests have higher accuracy, but pose a risk of miscarriage (according to Oster, 1 in 800).
Spoiling the punchline: cell-free fetal DNA tests have advanced non-invasive screening considerably from the ultrasound days.
Just as common as prescriptions on diet during pregnancy are prescriptions on activities like gardening and hot tubs. Here’s a run-down of common activities commonly barred during pregnancy.
Cats present a risk for toxoplasmosis only during the cat’s first exposure. Therefore, older cats that have already had it, cats that don’t eat raw meat, and cats that don’t hunt outside are less likely to have toxoplasmosis. If the cat has kittens when you’re pregnant, risk increases.
There is a strong association between working with soil and toxoplasmosis. So if you garden, wear gloves and maybe a mask.
The misconception around hair dye causing birth defects likely began with experiments that dosed animals at unnaturally high amounts. In humans, a study of hairdressers found a small but significant increase in low-birth-weight babies, but this was not replicated and may be due to other things (like standing a lot).
Hair dye is likely safe, particularly after the first trimester.
**Raising your body temperature above 101...
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Weight gain is a top topic for your prenatal care visits. Gain too much or too little weight, and the child is at risk (and your doctor will probably complain). Even more, the concept of “eating for two” may stimulate pregnant women to overeat.
Here are the guidelines for suggested weight gain over pregnancy:
|Starting weight||Suggested weight gain (lb)||Weight gain per week (lb)|
|Underweight (BMI < 18.5)||28-40||0.85|
|Normal Weight (BMI 18.5-25)||25-35||0.75|
|Overweight (BMI 25-30)||15-25||0.50|
|Obese (BMI > 30)||11-20||0.38|
If you start out underweight, you should gain 28 to 40 pounds throughout pregnancy, or 0.85 pounds per week.
If you start out normal weight, you should gain 25 to 35 pounds throughout...
About half of couples choose to learn about their baby’s gender before birth.
You can find your baby’s gender through a maternal blood test (soon after pregnancy), CVS test (first trimester), or in ultrasound (typically around 20 weeks).
If you don’t want to put your baby's gender to chance, you can dictate your baby’s gender...
There is little evidence suggesting that exercise has any effects on preterm birth, rate of C-section, length of labor, or baby APGAR scores. Exercise does show a modestly lower weight gain (1.3 fewer pounds).
Exercises to consider:
The baby is exposed to most drugs the mother takes, except for large molecules (e.g. [restricted term]) and drugs that get stuck in the placenta (e.g. [restricted term]).
Drug safety is hard to test in pregnant mothers because of ethical concerns - if there is risk of damage, then exposing a fraction of mothers to a drug seems unspeakable. Furthermore, medicine has a traumatic memory from the use of anti-nausea drug [restricted term] in the 1950s, leading to thousands of infants with birth defects and thousands of deaths.
Therefore, many drugs that are probably safe for pregnant women don’t get an explicit clearance from the FDA.
The FDA classifies drugs into five categories (A B C D X), based on strength of evidence on safety:
A premature birth occurs before 36 weeks and occurs in 12% of pregnancies. Early-term is between 37-38 weeks, and full-term is 39 and beyond.
Over the past decades, survival for preterm babies has increased dramatically due to improvements like assisted ventilation (lungs develop later in pregnancy). It’s a marvel that even babies born at 22 weeks still have a shot at survival.
However, premature children are more likely to get sick, have lower IQs, and may have vision/hearing problems. 75% of 5-year-olds born before 30 weeks have a disability (vs 27% of full-term births). Their IQs were 5-14 points lower.
Here’s a table of % of births occurring at each week of gestation:
|Weeks of Gestation||% of Births||Probability of Death in First Year|
This scary chapter goes through major complications of pregnancy in the third trimester, their consequences, and treatments.
(Shortform note: Oster did not include the baseline rates for these and risk factors, so we did the research and added them here (thus, any inaccuracies are not the book’s fault). Mercifully, the risk for any grave condition is usually <1%.)
Generally, if a particular complication happens in your first pregnancy, it’s likely to happen in future pregnancies.
What: Placenta covers the cervix, partially or fully.
(Note the vicious cycle here - placenta previa leads to C-sections, which increases risk of placenta previa.)
What: Placenta detaches from the uterine wall
As you cross the 36th week of pregnancy, you’re past the preterm period (hooray!) but then you start worrying the baby will never come out.
18% of babies are born week 38, 30% on week 39, and 17% on week 40. In sum, 70% of babies are born before their due date.
Here’s the chance of pregnancy for every week you reach:
|Week of pregnancy||Chance of birth this week if still pregnant this week|
Here’s a timeline of labor:
First Stage: Dilation (few hours to a few days)
Second Stage: Pushing (few minutes to a few hours)
Third Stage: Placenta (short)
Generally, labor progresses at an average of 1 cm of dilation per hour, but this rate can be slower in early labor (2 hours without any change in dilation) and speeds up near the end (going from 7 to 10 cm in < 90 minutes).
If the cervix doesn’t open quickly enough, you can be given [restricted term] to induce contractions or a C-section if the baby’s heart rate is dropping.
C-sections happen in 30% of births in the US, but they are not the preferred mode of delivery since they entail slower recovery. Once you have a...
Birth plans are short documents that describe what you want to happen during your birth and what treatments you’re willing to accept in which situations. OBs and nurses have a slight aversion to them because they may signal some inflexibility to do what they think is best in critical situations.
But Oster argues it’s far better to think about hard decisions and articulate your preferences beforehand than to come up with them on the fly.
Here are the elements of her birth plan:
The baby’s out! Now there are just a few more actions to know about.
Delayed Cord Clamping
Vitamin K Shots
<1% of women in the US have a home birth. If you’re high risk (breech, twins, gestational diabetes), you’ll probably need a hospital birth, as it’ll be hard to find a midwife to attend a risky birth.
Home birth supporters will say that delivering at home is how it’s been traditionally done. It’s more comfortable, and you don’t risk the hospital forcing you to get a treatment you don’t want. Studies also show that births at home show fewer vaginal...