What do they not mean when doctors say "limit your intake of x to y times or y amount per day?

I am a little confused by the question. You seem to be conflating two different things: avoiding something (which means don’t have it) and limiting something for some duration of time.

If I were to put the caffeine for pregnant women into the formula you have set up, it would read:

“Avoid caffeine for the duration of your pregnancy.”

Edited:
Except it is not me who does that, it is some pregnant women, and the readers of articles, who are addicted to coffee, the doctors who sell coffee etc. The best doctors just say avoid it, period. But again even some of the ones who say “limit it to…” may not be thinking “1 cup per day for the duration of the pregnancy.” Maybe they assume they wouldn’t be misunderstood?

If a doctor doesn’t make it obvious play it safe and avoid it altogether.

Considering how long caffeine remains in the body it should be not just have no caffeine during pregnancy but also while attempting to become pregnant.

Man. My kid was 10½ lbs, and basically the only stuff I could hold down during my pregnancy was coffee and Dr. Pepper.

Guess I skipped that whole low-birth-weight thing.

It also bears mentioning that exactly no human pregnancy takes 365 gestation days.

Study lead author Kristen Hahn, an SPH research fellow in epidemiology, says the risk of miscarriage peaked at consumption of around 200 milligrams a day, followed by a decline in risk at higher levels of intake.

…

Hahn says that although the study is larger and more extensive than prior ones, its findings still leave questions about caffeine’s impact, because there was no evidence of a “dose-response relation” between increasing consumption of caffeine and higher miscarriage rates.

source

No dose-related response in increased (and then, decreased) risk of miscarriage.

Correlation =/= Causation.

If they meant otherwise, they would say so. For instance, there are foods I’ve been told I can only eat 1–2 servings a week. Some meds I’ve been on interact with alcohol, but not so badly that I must be an absolute teetotaler; I can have a (as in one; singular) beer once in a while.

If they don’t want you doing something every day, they will specify, “No more than X times per WEEK”.

As for citing those studies, realistically you can find proof of anything. If you believe everything you read, then the entire human race is all autistic, cancer-ridden people. But let us take the first thing Google listed when I searched for “Caffeine pregnancy”; just those two impartial words with nothing like “risk” or “avoid” or anything else to slant the results.

“Statement: Caffeine causes birth defects in humans.

“Facts: ... There have not been any conclusive studies done on humans…

“Statement: Caffeine causes miscarriages.

“Facts: In 2008, two studies on the effects of caffeine related to miscarriage showed significantly different outcomes…Due to conflicting conclusions from numerous studies, the March of Dimes states that until more conclusive studies are done, pregnant women should limit caffeine intake to less than 200 mg per day. This is equal to about one 12 oz cup of coffee.”

“Statement: A pregnant woman should not consume ANY caffeine.

“Facts: Experts have stated that moderate levels of caffeine have not been found to have a negative effect on pregnancy. The definition of moderate varies anywhere from 150 mg – 300 mg a day.”

Okay, let’s look at WebMD since so many people trust it.

”“For years, women have been getting mixed messages about whether or not they should have any caffeine during pregnancy,” says William H. Barth Jr., MD, chair of ACOG’s committee on obstetric practice, in a news release. “After a review of the scientific evidence to date, daily moderate caffeine consumption doesn’t appear to have any major impact in causing miscarriage or preterm birth.”

Well, at a glance, it looks like most doctors agree that moderate caffeine consumption is fine, even daily. I read through a few more results just to make sure, and the only thing I saw saying pregnant women couldn’t drink a cup a day was your question. I suspect that the only way you could find evidence to the contrary is to look for it, which would be confirmation bias.

I have a prescription for 3×10mg Valium per day. I’m pretty sure it doesn’t mean I can take 30 mg all at once. Although it would probably be entertaining. Add in a couple beers and I would be awfully relaxed.

Still confused.

@majorrich Same for me and Ritalin; wash a few down with some espresso and, due to my bizarro blood chemistry, I would be relaxed, and possibly quite entertaining too.

@flo: Just FYI, I drank caffeine every day when I was pregnant, and I had a great pregnancy and a perfect baby.

@jerv The pregnant women who just don’t want to take a chance, avoid it and stick to drinking water and homemade juices of fruits and vegetables, etc. There would be no confirmation bias, or…whatever else.

Could it be that the studies that say it’s okay go ahead drink x y z amount/per day funded by the coffee sellers or addicts to coffee?

@majorrich and @Cosmos I agree.

@Tropical_Willie Would you elaborate?

@Seek and @jca The question is not whether or not there are some people who had no problem. If that were the case, there would never ever be any study about anything.

To answer the question precisely,

Yes, one cup of coffee per day means one cup of coffee each day is fine.

Not 365 days, unless your fetus is an elephant.

Added:
@Seek Why the need to repeat yourself? I believe you haven’t read the airtight response I gave at my response to @jerv as well?

I don’t think anything about this discussion is airtight.

@flo “Could it be that the studies that say it’s okay go ahead drink x y z amount/per day funded by the coffee sellers or addicts to coffee?”

Given the weight of the evidence, I doubt it. Assuming that all the scientists could even be bought, the price would be enough that it would be reflected by coffee being considerably more expensive than it is.

If one has a belief system that dictates that they avoid caffeine entirely during pregnancy then there is no harm in it, though it would not be supported by scientific evidence. Compare the number of people who go gluten-free “for health reasons” to the number of people that actually have certifiable issues with gluten (like Celiac’s) and you will see that many people do “healthy” things that are not conclusively proven in any sort of peer-reviewed studies.

But unlike, say, choosing to not vaccinate your kids out of fear of Autism, there is no harm in going the whole coffee-avoidance route. I know plenty of non-pregnant people who are quite sensitive to caffeine and thus don’t drink coffee anyways. About the only thing that there is anything conclusive on is that high levels of caffeine are bad. The funny thing is that the limits is that they were more than I take in, and some people consider me to be “addicted to caffeine”; levels far above what most people could tolerate period. We’re talking 200–300mg/day compared to the 400mg/day limit for non-pregnant people.

In other words, pregnancy doesn’t affect the recommended daily maximum terribly much. It’s still high enough for a single Latte, per day…. though as the caffeine content of coffee varies (90–200mg per 8-ounce serving), you’ll want to limit yourself to a 12-ounce. As regular cola is only about 30–40mg per 12-ounce can, it’s actually a better bet for those wishing to curb their caffeine intake. A six-pack of canned Pepsi is a little under 240mg/day, and even many non-pregnant people would consider that a bit excessive. Trust me, I only drink about that much and I get comments on my caffeine consumption.

Now, if you want to make the argument that EVERYBODY, pregnant or not, consumes too much caffeine, that is a separate discussion.

@jerv All the proof that’s needed,, look how much energy you’re wasting on defending coffee/caffeine. Key word defending. Let’s see you say to @Seek or @jca for example “C’mon you two that is not really an answer., whether or not your baby is perfect”
Or ” @Seek That’s just a distracting move re. the 365 days thing, not an argument”

Um, it is if you’re referring to pregnant women and not pregnant elephants.

@Seek Lets go. I don’t think we can do anything here.

Added:
...Not to mention that to mothers all their children are perfect even if they have birth defect. Also they will not say “I may have caused this problem for my child because of my addiction”