As we have seen in this series, there is a move afoot to lower the pregnancy weight gain guidelines from the Institute of Medicine (IOM). We've discussed the people behind this push, and we've discussed what advice fat pregnant women are actually receiving about weight gain.
Now the question is, how much weight do most fat women actually gain in pregnancy? Do most follow the "only gain 15 lbs." rule? Do most gain more? Less? It's one thing to have guidelines on paper, it's another thing to see what happens in real life.
Many doctors and research articles contend that fat women gain "excessively" in pregnancy. The way this is phrased in the media spin makes it sound like fat women are stuffing down everything in sight because being pregnant gives them an excuse to "eat for two," and that they are all out of control, gaining huge amounts of weight.
Yet if you look at the research studies, they consistently find that fat women gain LESS weight than average-sized women. But because the IOM threshold for fat women is 15 lbs., what is a "normal" gain for every other woman (25-30 lbs. or so) is automatically categorized as "excessive" for fat women.
So when you read that research shows overweight and obese women are "gaining too much weight," remember that this is because they are being held to a different, stricter standard.
Is this a fair and realistic standard?
If you look at the graphic above, even if fat women gain NO weight for fat/protein stores, and gain the least amount of weight in each of the other categories, the minimum weight gain is 17 lbs. And yet fat women are regularly told to only gain 15 lbs., or almost none if you go by the new standards some doctors are pushing. How is this a realistic standard?
Furthermore, much of the prenatal weight gain research is tainted by inadvertent errors. The fact is that many fat women actually lose weight in the first trimester or so of pregnancy. However, pregnancy weight gain is often calculated from the first prenatal appointment, so any first-trimester loss is often not accounted for in official records. So researchers may be overestimating pregnancy weight gains in women of size, unless they figure gain from your pre-pregnancy weight.
The point is that these "excessive" gains being recorded in fat women are often because researchers are holding fat women to a stricter standard than average-sized women, and because they often figure gains from the first prenatal weight, rather than from pre-pregnancy weight. So the reports tend to get distorted.
But that leads us back to the question.....what do fat women REALLY gain in pregnancy, in REAL life? What's a realistic standard?
Highly Variable Gains
When you look closely, what you find is that there is a LOT of variability in the weight gains of fat pregnant women. Many fat women gain about 15-25 lbs., while others gain <15 color="#000000">All of these may be variations of NORMAL. The truth is that fat women's weight gains are all over the map. Even when mothers' nutrition is excellent and they are getting regular exercise, a wide range of weight gain is not unusual.
This is reflected in my own data. Over the years, I have collected the birth stories of several hundred women of size, from women who are just barely plus-sized to women who weigh over 400 lbs. You can find these stories at my website, http://www.plus-size-pregnancy.org/, in the "BBW Birth Stories" part of the site.
As a way to help categorize the stories, I asked each contributor to enter data about her pre-pregnancy weight and weight gain in pregnancy. This gives me a database of information about pregnancy in women of size to pull from. Because it's taken from stories women submit, it's not a truly scientific database, but it still can offer some insight into the way that women of size gain.
My data upholds the idea that weight gain in pregnant women of size is highly variable.
- The largest group of gains is the 0-15 lbs. group, with most of these women falling in the top 2/3 of that range (5-15 lbs.)
- Then comes the 15-25 lbs. group, with the group equally spread within this range
- Close behind is the 26-35 lbs. group, with most of the gains in the bottom to middle (around 26-30 lbs.)
Although the results are not equal between these three groups, they do tend to be fairly well distributed. The vast majority of large women will fall into the first two groups, with a slightly smaller (but still significant) group in the third category. In other words, most fat women gain somewhere between 5-30 lbs. during pregnancy.
Doctors who want to lower the weight gain standards for women of size claim that lower gains will help lower the risk for cesareans in this group. However, the data from my site doesn't support this idea. The majority of women who had cesareans actually had gains in the 0-15 lbs. range. An increase in excessive weight gain was not the cause of the cesareans in this group. More often, cesareans there seem to be due to fetal malpositions or failed inductions.
Weight Gain Patterns Along the Fringes
But what about the fat women who had a cumulative weight loss or a high weight gain during pregnancy? Although these were outside the usual gains of most women of size, they're not all that unusual. But if you read the stories of these women more closely, you begin to notice some patterns.
Those who had a cumulative weight loss during pregnancy often tended to be those who started at very large sizes, or those who experienced problems like severe nausea in pregnancy or hyperemesis. Most do not recount being put on hypocaloric diets, but note that the weight loss happened "without trying" or in spite of their efforts to gain weight. Although the reason for this is unclear, it may be that in some women, pregnancy improves their metabolism so strongly that a net loss occurs.
Those who had high weight gains in pregnancy often were those who experienced pre-eclampsia (where fluid retention tends to make weight gain larger than normal), those who were chronic yo-yo dieters, those who had eating disorders (bulimia or binge eating disorders), or those who had lost a great deal of weight just before pregnancy.
For example, one woman has 7 birth stories on my site (she has since had more babies). She is courageously frank about having a strong history of bulimia and starting her first pregnancy at a lower-than-usual weight. Once she stopped purging, she gained 110 lbs. in that pregnancy. In later pregnancies, after her weight had stabilized at a higher weight, she gained anywhere from 0 to 30 lbs. each time. In one pregnancy where she had a terrible case of hyperemesis, she lost a total of 23 pounds. In another pregnancy where she had deliberately lost 115 lbs before the pregnancy, she gained 60 lbs.
So in one woman, pregnancy weight gain varied from a loss of 22 pounds to a gain of 110 pounds.....quite a wide variation, but perhaps not unexpected in someone with such a tumultuous weight history. (However, we should hasten to add that even when she gained 110 lbs., she still had a vaginal birth, something some doctors would lead you to believe is impossible. Such a variety of weight gains is not ideal, yet in the end her outcomes were okay.)
In the extremes of documented gains on my website, the lowest "gain" was a loss of 54 pounds, and the highest gain was the one listed above, +110 lbs. So while the majority of gains fell in the 0-15 or 15-25 lb. category (and this is probably the most realistic ideal), there really was quite a variety of weight gains documented.
This is echoed in the 2003 research in the "International Journal of Obesity," which compared weight gain in Finnish women between groups in the 50s/60s, in the 80s, and in 2000-2001. They found:
Overweight women gained the least weight in all the three cohorts. These findings are similar to the results from earlier studies....Obese women gained the least. On the other hand, variation in pregnancy weight gain has been the largest among overweight and obese women.
So large women tend to gain LESS than average-sized women, but their gains are highly variable and may range from very large gains to quite large losses.
Still, MOST fat women tend to gain in the middle, either in the 0-15 lbs. range or the 15-25 lbs. range. Some doctors will see this as justification for lowering the IOM guidelines, but again, that's just not very realistic. Although many women gained in the 0-15 lbs. range, most in this category gained in the 5-15 lb. side of the range. Very few women gained <5>
Although some fat women do gain little/no weight (or even lose weight), is this a realistic goal for most fat women? Is it even a healthy one? How possible is it really to manipulate weight gain anyhow? And what might the fallout be of restricting the pregnancy gain of someone who would otherwise gain normally? Do we even know? Aren't we playing with dynamite to try to manipulate things like this?
Generalizations About Weight Gain Patterns in Women of Size
There are some typical weight gain patterns in women of size. They don't hold true for EVERY fat woman, but there are some general trends you can pick out.
In general, the larger you start, the less weight you tend to gain. Women who tend to have larger gains usually are the ones lower on the BMI scale to begin with, and women who are high on the BMI scale usually tend to gain less. (However, there are plenty of exceptions to this!)
Fat women at greatest risk for large weight gains include those who develop complications like pre-eclampsia (where fluid retention is a common symptom and distorts total weight gain), and those who have dieted recently or who are chronic yo-yo dieters.
Women who diet chronically or lose a large amount shortly before pregnancy may gain extreme amounts. This is probably because the 'rebound' phase that often occurs after dieting may be intensified by the pregnancy's need to have adequate fat reserves for later (i.e., if it feels 'starved' after dieting, so it overcompensates during the pregnancy).
[This is one of the problems with the common medical advice to lose weight before pregnancy; these women often then have tremendous weight gains in pregnancy afterwards. One big mom I knew lost over a hundred pounds before pregnancy, only to gain 80 of them back during the subsequent pregnancy. Another woman on my website lost 90 lbs. before pregnancy, only to gain back 65. It is questionable how healthy such wide swings of weight in such a short period of time.]
All in all, if you are a woman of size and eat normally and healthfully, nature will likely keep your weight gain slightly lower than women of average size. This may be because women of size already have fat reserves and don't need the extra reserves that other women tend to add in pregnancy. It may also be because many fat women (especially those with PCOS and/or hypothyroidism) find that pregnancy tends to increase their metabolism.
Gaining too much weight may cause problems in pregnancy, so women of size should try to avoid excessive gains, but nutrition always trumps weight gain. A larger weight gain may simply be a variation of normal for some women; as long as they are eating healthfully and getting regular exercise it may not be a reason for excessive concern. It is certainly not a reason to put a woman on a diet in pregnancy or to schedule an automatic cesarean.
Remember, women of size do seem to have a wide variation of "normal" gains, depending on a variety of factors. Trying to manipulate weight gain through extreme means in order to meet artificial guidelines is probably an unrealistic pursuit, and possibly even be a dangerous one.
The best course is probably to eat healthily, exercise regularly, and let nature take care of the rest.