Fat and pregnancy: resources for debunking risk factor myths

This blog does not set out to directly debunk the myths surrounding the dangers between fat and health. There are other sites that focus on this, though, as a mathematician, I will from time to time step in and have a few choice words about research-based statistical analyses (which are 80% of the conclusions made by most authors). I’d argue, in fact, a mathematician is the best interpreter of the real results of these studies, and not medical professionals. But that’s neither here nor there.

I did, however, want to compile a list of resources which will help fat pregnant women (or fat women who want to become pregnant) debunk the junk science correlations between fat and reproductive disorders and pregnancy complications. Often such studies are done on fat infertile women, or fat women with PCOS, and applied in blanket, press-release fashion to all fat women. Other studies can’t even find the correlations they’re looking for, unless they chop their study group down to a statistically meaningless size, or don’t correct for comorbidities (like PCOS or family history) when making conclusions about correlations.

Here is the list so far. I will be editing this from time to time, and will keep this post linked on the sidebar for easy access.

If you want to search on your own, I recommend this particular search of Junkfood Science’s archives.

Another blank missile fired at fat pregnant women

The study, published in the New England Journal of Medicine, was led by Susan Y. Chu, Ph.D, and colleagues at the National Center for Chronic Disease Prevention and Health Promotion at the CDC and Kaiser Permanente*. The primary objective of this study “was to estimate the maternal healthcare services associated with obesity during pregnancy.” More precisely, they were looking for correlations between pre-pregnancy BMIs and length of hospital stays when the women had their babies.

After they adjusted for age, multi-parity (number of pregnancies), race, delivery and other conditions, the total hospitals stays averaged 4.4 days for the “normal” weight and “overweight” women … and 4.5 days for all of the “obese” women, regardless of how fat they were.

Fat women of child-bearing age targeted again:

The 2001 study cited, was a retrospective analysis of a maternity database, which had recorded women’s BMIs when they were booked at maternity units in London. The authors from the Imperial College School of Medicine at St. Mary’s Hospital used computer modeling to look for correlations to pregnancy outcomes. Interestingly, they redefined ‘obesity’. Women with BMIs 25-29.9 (labeled worldwide as “overweight”) were defined as being “moderately obese,” leading to a larger group of “obese” women which would overstate any correlations with ‘obesity.’ The risks associated with “obesity” were also reported as odds ratios — a way to compare two groups based, not on actual incidences of stillbirths, but by comparing odds and can greatly exaggerate correlations that aren’t actually significant.

Even so, this study still found no tenable correlations between high BMIs and intrauterine deaths (odds ratio 1.10-1.40), nothing beyond random chance and happenstance.

Another study cited in the review, as supporting risks for stillbirths four times greater among ‘obese’ women compared to ‘normal’ weight women, had been published in the American Journal of Public Health. … Here again, the authors reported correlations as odds ratios. Despite all of this, however, the researchers were unable to find any correlations with adverse pregnancy health outcomes that were tenable and beyond what might appear by chance. And concerning stillbirths? As the authors said: “We were unable to include fetal death as an outcome because the birth certificate database includes only live births… we were unable to assess the risk of fetal death in relation to maternal BMI.” So, this study cited in the Australian review didn’t support its assertion of a higher risk for stillbirths.

The final study cited in this review paper as evidence of higher stillbirths associated with obesity was an observational study using data from computer-assisted telephone interviews of women in Denmark. … They also reported the correlations using odds (hazard) ratios. Overall, the Danish study found no tenable association between BMI and fetal deaths from 13 weeks gestation to >40 weeks. There was also no correlation between pregnancy weight gain and stillbirths, nor were risks for stillbirths associated with “obesity-related” diseases in pregnancy.

Pre-eclampsia: a disease of malnutrition

But perhaps the single biggest factor which has been linked to pre-eclampsia is poor diet: if a woman is malnourished and living in a stressful environment, the risk is even greater. Unfortunately, many practitioners are ignorant of what constitutes a proper diet for pregnancy. When nutrition is studied, the research shows an obsessive focus on single nutrients, like magnesium, given in isolation, instead of a holistic dietary approach.

In the meantime, the published evidence on diet is very clear. The only clinicians who have managed to completely eradicate pre-eclampsia are those who have taken steps to ensure women are fed properly. This means receiving daily high protein in the form of milk, eggs and meat, as well as daily servings of leafy green vegetables and fruit. The daily calorie intake should be around 2,800 and should include 80-100 g of protein.

Common sense, some would say, yet so many doctors still recommend calorie and weight restriction during pregnancy, forgetting that a diet for pregnancy is not necessarily a diet for life. This tunnel vision may only worsen with a recent study which concluded that the “liberal” weight gain now recommended (25-35 pounds) during pregnancy is not necessary (Lancet, 1998; 351: 1054-5).

Science by press release

Today’s media has been filled with stories of a new study by Dr. Artal and colleagues at St. Louis University School of Medicine, purportedly showing that fat pregnant women should lose weight to avoid pregnancy complications and avoid having a fat baby. “Obese women don’t have to gain any weight during their pregnancy,” he said in the press release. “Pregnancy is a big factor in this [obesity] epidemic.” … “The findings are significant in addressing a major public health crisis …. This study confirms what we’ve suspected all along — that obese women don’t have to gain any weight during their pregnancy,” Dr. Artal said.

But it didn’t.

This was not an interventional trial to examine if controlling weight gain improved pregnancy outcomes, it was an observational study looking for correlations among a database of ‘obese’ pregnant women in Missouri who delivered term babies (37 or more weeks gestation) from 1990 to 2001.

The women who were heaviest, for instance, were also more likely to be poorer, minority women and most likely to delay seeking prenatal care. As the March of Dimes explains, for instance, pregnant women facing very stressful situations, such as low socioeconomic status, long working hours, strenuous or stressful work, long commutes to work or unemployment, have higher rates of preeclampsia. So, not surprisingly, slightly higher preeclampsia rates were also correlated with the heavier women in this cohort. Another important note is that the heaviest women in this study population were also older and higher maternal age is also associated with higher rates of gestational diabetes and preeclampsia. Good prenatal care can effectively care for these conditions to ensure safe pregnancies and healthy babies.

More resources will be added later.

Have resources/articles debunking fat as a risk factor for pregnancy and reproductive complications? Please post them using the comment field below.

One comment on “Fat and pregnancy: resources for debunking risk factor myths

  1. vesta44 says:

    Every time I read something about how dangerous it is for a fat woman to become pregnant, I get livid. I was overweight the first time I got pregnant (at 17 1/2) and I was overweight the second time I got pregnant (in spite of being on the pill). I was morbidly obese the third and fourth times I got pregnant (I had an IUD both times). Obviously, my fertility wasn’t affected one little bit by the amount of fat I was carrying on my body. I ended up having to get my tubes tied to prevent pregnancy (and I was only 25 at the time). So any time a doctor says fat women have a harder time getting pregnant, I laugh. My first 2 pregnancies were quite normal, no complications, and vaginal births for both of them. I don’t know about my daughter’s health (I gave her up for adoption), but my son’s health is just fine (and he’s 33 now). My last 2 pregnancies were terminated (my choice), but were normal up to their termination. I know my experience is anecdotal, but there are probably a lot of women just like me out there who are fat and have had no problems with getting/staying pregnant and have had no problems with their pregnancies. Thing is, researchers are too good at picking and choosing the populations they use, and it’s very easy for them to eliminate women who won’t support the conclusions they’re looking for. That’s why I view most research on fat with such suspicion (yeah, I’m a cynic from way back).

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