My obstetrician said some coffee was fine, but I should stick to less than two cups (again, that’s a 235-millilitre cup).Read more at location 901
The big concern with caffeine and pregnancy is that it might lead to higher rates of miscarriage.Read more at location 904
Caffeine can cross the placenta and it’s not clear how the foetus processes it. In addition, researchers have speculated that caffeine can inhibit foetal development by limiting blood flow to the placenta. This is a case where the biological story on its own is not very compelling; although there is speculation about these effects, they have not been proven.Read more at location 904
What has been shown in a well-controlled way is that very high doses of caffeine do cause miscarriage in mice and rats. But these doses are much, much higher than what people consume. In order to produce pregnancy problems in rats, researchers require something like 250 milligrams of caffeine per kilogram per day. Translated to a human of 10 stone, 10 pounds? That’s a bit more than 60 cups of coffee per day.18 I challenge you to even find the time to drink that much!Read more at location 907
Studies of the impact of caffeine on miscarriage have another problem, one that makes caffeine even harder to study than alcohol: nausea. Nausea is an unpleasant part of early pregnancy, one that most women experience. But (more on this later) it’s also a really good sign about the health of the pregnancy. Women who experience nausea in early pregnancy are less likely to miscarry (it is not clear why this is the case; nausea may reflect hormone levels, but that’s just speculation). Why is this a problem?Read more at location 914
We know that nausea is a sign of a healthy pregnancy. At the same time, it also causes women to avoid coffee. But this means that women who drink a lot of coffee are probably those who are not experiencing nausea. These women are more likely to miscarry. But you might be wrong to conclude that coffee causes miscarriage;Read more at location 921
Researchers try to “adjust” for this – asking women whether they experienced any nausea, for example – but this is hard to do. Nausea isn’t a yes-or-no thingRead more at location 925
Even with this nausea issue, many studies suggest that in moderation there is no strong link between caffeine and miscarriage.Read more at location 928
Perhaps my favourite study of this question is a recent one from the University of Maryland published in 2010. The researchers followed a group of women starting when they tried to get pregnant. They collected daily diaries of their diets, including caffeine.Read more at location 935
This study found no relationship between caffeine and miscarriage. The big drawback, however, is the sample size: with data on only 66 pregnant women means this study is suggestive but not conclusive.Read more at location 939
Consider one covering about 2,400 women published in the journal Epidemiology in 2008.20 Women enrolled in the study either while they were trying to get pregnant or at their first antenatal check-up. Information on coffee consumption was collected at 16 weeks of pregnancy and miscarriage was recorded up to 20 weeks.Read more at location 941
Among the women who reported drinking no coffee, the miscarriage rate was about 10 percent. Women who consumed a half cup to two cups a day had a slightly higher rate, but this difference is small. It’s also not statistically significant.Read more at location 951
Women who consumed even more coffee (more than two cups a day and more than three and a half cups a day) had, if anything, lower rates of miscarriageRead more at location 954
This isn’t the only study to come to this conclusion – one in Denmark with almost 100,000 women similarly found no impact from up to three cups of coffee a day.22Read more at location 958
Around the same time this 2008 study came out, a similar study was released in California. The study design was very close: researchers recruited women early in pregnancy, interviewed them about how much coffee they drank and measured miscarriage up to 20 weeks. However, despite the similar design, the researchers came to somewhat different conclusions.Read more at location 960
researchers found no difference in miscarriage rates between women who drank no coffee and those who drank up to two cups a day. However, they did find higher miscarriage rates for those who drank more than two cups a day.Read more at location 965
For some women and for the American Congress of Obstetricians and Gynecologists, this study may be enough to conclude that pregnant women should stick to less than two cups a day. For me, however, there were enough aspects of the study that gave me pause and suggested that perhaps this is just the nausea story all over again.Read more at location 968
For one thing, the authors found no effect of coffee among women who reduced their consumption, regardless of what their final consumption level was. Taken literally, this means that it doesn’t matter how much coffee you drink, as long as you reduce from your starting level.Read more at location 970
Note: STRANEZZADELLI STUDIO: BASTA RIDURRE IL CONSUMO... BI LIVELLI ASSOLUTI NN COBTANO. CHIARA INTERFERENZA XEFFETTO NAUSEA Edit
As I poked around this research, there were a few other things that made me think the nausea story might be quite important. One was that other common sources of caffeine – tea and cola – are less consistently linked with miscarriage.25 These contain caffeine (although less than coffee), but tend to be easier on the stomach, so the confounding relationship with nausea is limited.Read more at location 981
I also found one clever study that showed that decaffeinated coffee was as strongly linked to miscarriage as caffeinated coffee. Decaf coffee has the same nausea problem, but no caffeine.Read more at location 985
I decided the three to four cups a day I was having was fine.Read more at location 989
The evidence is better for the simple reason that there is at least one randomised controlled trial (I guess it’s not impossible to get this by an ethical review board, just difficult). Researchers in Denmark recruited 1,207 pregnant women who were coffee drinkers (at least three cups a day). They were asked to be in the study before 20 weeks of pregnancy and the researchers recorded the birth weight of their babies and whether they were premature.Read more at location 996
Now here is the experiment: women were given free instant coffee. Half of them were given free caffeinated instant coffee and half were given free decaffeinated instant coffee. The women did not know which type of coffee they received (the boxes looked the same). They were asked to replace their usual coffee with the instant coffee from the study.Read more at location 1000
The caffeinated-coffee women had babies of the same weight and length after the same number of days of gestation and with the same head size. Other, non-randomised studies have reached similar conclusions.Read more at location 1026
The first thing to note is that studies of women at this higher level of consumption are, if anything, even more subject to the concerns about nausea. If you are feeling at all nauseous, at any time of the day, you are probably not having eight cups of coffee. Perhaps for this reason – or, perhaps, because too much coffee really is a problem – studies are more consistent at showing a linkRead more at location 1031
The Bottom Line • In moderation, coffee is fine. • All evidence supports having up to two cups. • Much of the evidence supports having three to four cups. • Evidence on more than four cups a day is mixed; some links are seen with miscarriage, but it is possible that they are all due to the effects of nausea.Read more at location 1053
If you smoke, your doctor has presumably encouraged you to quit. But quitting is hard and most smokers have tried at one time or another. The question in the case of pregnancy: is there any extra reason to quit while pregnant? The answer is a resounding yes. Smoking, even in moderate amounts, is bad for your baby.Read more at location 1060
higher risk for SIDS (sudden infant death syndrome, often called cot death).Read more at location 1063
Tobacco contains a number of chemicals, but the two important ones are nicotine and carbon monoxide. Both of these restrict oxygen to the foetus. Less oxygen means less growth. Additionally, the blood vessel constriction caused by nicotine exposure can damage the placenta, which is the source of many pregnancy complications.Read more at location 1065
Consider a representative study that analysed all births in Missouri, USA, between 1989 and 2005 (this amounted to more than one million babies).31 The authors in this study simply looked at whether women said they smoked during pregnancy and compared women who smoked to those who did not.Read more at location 1068
Women who smoke are more likely to be anaemic and are much more likely to have problems with the placenta and to have pre-term labour or stillbirths. The impacts on birth weight are huge: if you smoke you are more than twice as likely to have a baby who is very small.Read more at location 1099
Maybe moderate smoking is okay? No, it is not. The study in Missouri showed that women smoking one to nine cigarettes a day had just has many extra complications as those smoking more than a pack.Read more at location 1102
Does it matter when during pregnancy you smoke? A study from the Netherlands published in 2008 looked at the timing of smoking.32 These authors found that smoking later in pregnancy had the largest effects on birth weight.Read more at location 1104
Women who smoked more than nine cigarettes a day after 25 weeks had babies about 200 grams smaller than those who did not smoke; this is a 6 percent reduction in body weight! This means, among other things, that even if you smoke at the start of pregnancy, there are still huge benefits to quitting later on.Read more at location 1106
A study in the United Kingdom described differences in the risk of cot death in children of mothers who smoked and those who did not.33 Children of mothers who smoked one to nine cigarettes a day during pregnancy were more than four times as likely to die of cot death as those whose mothers did not smoke. Children of mothers who smoked 20 or more cigarettes a day were almost nine times as likely to die. Here is another way to look at it: 86 percent of cot deaths in the UK were among children of mothers who smoked.Read more at location 1109
Second-hand smoke exposure (for example, from fathers or grandparents) also leads to many of the same negative outcomes. A 2010 review article found that babies of mothers who were exposed to second-hand smoke during pregnancy were about 57 grams lighter at birth than babies who were not.34 It’s worth saying that the women in these studies were exposed to a lot of smoke, like the amount that would come from living with a partner who smokes. Very occasional contact (a night with smokers, or walking by someone smoking on the street) is not a big deal.Read more at location 1116
precisely because people are convinced that smoking is bad and because it is hard to stop, there are randomised trials that do exactly the opposite: encourage women to quit smoking. Typically, these studies take a group of pregnant smokers and randomly assign half of them to some treatment that will hopefully reduce their smoking. If some of the women do quit smoking, we can learn about the impacts of smoking by comparing their babies with the babies of women in the control groups.Read more at location 1128
A 2008 review article summarised 64 studies just like this,36 16 of which also collected information on the babies. One thing we learn is that it’s really hard to quit smoking: of these 16 trials, only five actually got a significant number of women to quit. But among those studies we see benefits for the baby: women who were encouraged to quit had babies who were about 57 grams heavier.Read more at location 1131
The impact of not smoking must be very large if we can see differences in average birth weightRead more at location 1136
A final note: the best option is to quit smoking cold turkey as soon as you find out you are pregnant, or, ideally, before.Read more at location 1145
The Bottom Line Smoking during pregnancy is dangerous for your baby. *It’s hard to know why this is. As foetal alcohol syndrome is typically a result of binge drinking, it is possible that it could be due to the United States having more inequality in drinking – a lot of people not drinking at all and a few engaging in binge drinking – as opposed to European countries where most people drink moderately. **This graph reports co-efficients adjusted for maternal demographics and weight. ***This particular study observed a lot of information about children – including information on the drinking behaviour of the father – and after adjusting for everything about the child, they still found that test scores were unaffected by maternal drinking in pregnancy. ****These figures take the miscarriage rate for zero cups as the baseline and calculate the higher-intake groups by multiplying this baseline by the adjusted hazard ratio. You can read this as saying: if the group drinking eight cups of coffee was similar on all the other variables to the zero cups group, their miscarriage rate would be 1.9 percent, versus 1.2 percent in the zero cups group.Read more at location 1154
