Junkfood Science: Fat women of childbearing age targeted again

June 09, 2008

Fat women of childbearing age targeted again

For fat women who are expecting a baby, recent news has been delivering a continual barrage of stories that has left them frightened and worried. Pregnant women have heard that because of their fat, they put a strain on hospitals and that their babies are at higher risk of being born stillborn. Heavens, how does news like that help anyone? Before women add more worries to what is already naturally one of the most anxious times in their lives, remember that news stories are not research and just because something is said in the media — and in growing frequency — does not mean that there’s a growing body of new evidence... or any at all... to make it true.

As we look at the main stories in the news recently, we again find that the evidence paints a very different picture from what we’re hearing.

Hospital resources

The first story came when recent headlines in Canada blamed fat expectant mothers for putting a strain on hospitals due to their fat. It turns out, there was no research being reported, only sensationalized claims — claims which defied reason and available evidence.

Canwest News reported of an “obesity crisis: a growing proportion of dangerously overweight or obese expectant mothers,” saying that “one Edmonton doctor estimates that as many as 1,500 extra days in hospital are being spent in his region each year for new mothers due to obesity-related risks.” But this assertion wasn’t supported with any documentation.

As we recently saw when a similar claim was made in the United States, research examining 19,538 women, published in a recent issue of the New England Journal of Medicine, found no difference in hospital stays related to pregnant women’s weights.

The Canadian article went on to make an even bigger larger-than-life claim. According to the reporter, “obstetricians say it's not uncommon today to see women with a pre-pregnancy BMI of 50 or greater.” (‘Obesity’ is defined as a BMI of 30 or more.) The number of people with a BMI ≥ 50 is about 0.5%, according to recent statistics here. It defies reason that just across our borders, this weight would be common among young Canadian women of childbearing age.

The article goes on to quote Dr. Jan Christilaw, an obstetrician/gynecologist at B.C. Women's Hospital in Vancouver, as saying: “We do have a fairly large group of women [with a BMI of] between 30 and 35.” [This would equate to a 5ft 5-inch woman, weighing about 180 pounds — an example can be seen here.]

Yet, in this news story fat women were blamed for taking more hospital manpower. According to obstetrician Dr. Lawrence Oppenheimer at the Ottawa Hospital: “You might need two, three surgeons to do the procedures for a caesarean. It depends how big the patient is. To put it bluntly, you literally have to hold back the fat. You have to have more retractors and more people retracting.”

How many readers bought that it takes three grown men to hold back the fat of most fat pregnant women? Look at that example photo again of what a typical ‘obese’ woman looks like and ask yourself if this doesn’t sound more than sensationalized.

Before letting overly dramatic story telling take us in, or worry us, remember to look for the evidence. Anecdotal claims, regardless of the source, are still anecdotes.

Studies suggest...

The second news story was especially frightening, warning that fat women risk having dead babies. The news told us of a study that reported an alarming and unprecedented rate of increasing obesity and excessive weight gain during pregnancy in western societies. Being fat was said to be associated with higher pregnancy complications and stillbirths, with pregnancy weight gain an independent risk factor.

This study being described in the news, published in the Australian and New Zealand Journal of Obstetrics and Gynecology, wasn’t a clinical trial or what most consumers think of when they hear about a study. It was a review article that had compiled published papers to support an “association of maternal obesity with pregnancy complications.” The Australian authors laid out their premise in the first paragraph, when they wrote: “A global epidemic of obesity is unfolding... dramatic increase in the incidence of overweight and obese women of child-bearing age, rais[es] particular issues for the management of pregnancy in obese women. In developed nations, obesity is mostly attributable to sedentary lifestyle habits and the ready availability of high-energy food.”

Despite claims of an unprecedented epidemic of obesity across developed countries, as has already been covered at JFS, there have been no increases in rates of ‘obesity’ among women in the United States since 1999, according to the Centers for Disease Control and Prevention. Similarly, the percentages of ‘obese’ women of childbearing age across the UK has been flat at least since 1998, according to the most recent Confidential Enquiry into Maternal and Child Health report. Obesity rates are being reported as level over recent years in New Zealand and they’ve also been level in Canada at least since 1998, according to Health Canada.

Turning to the evidence this review used to support its claims that ‘obese’ women have higher risks of stillbirths also finds the evidence greatly lacking. In fact, the interpretations of these studies differed considerably from the actual findings and the conclusions of the original authors. Yet, how many healthcare professionals hunted down the original articles to see if the evidence being referenced actually supported the claims and conclusions being made?

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. In this study, epidemiologists at the University of Washington in Seattle, gathered birth certificates from 1992-1996. Maternal weights have been recorded on birth certificates in Washington State since 1992, but the Washington authors noted that “it is unclear what proportion of the weight entries were from a prepregnancy visit and what proportion were self-reported at the time of delivery.” The birth certificates also have a check-box format which the authors used to collect demographic characteristics, pregnancy complications, procedures and the condition of the baby. Self-reported heights were obtained from State drivers’ license records and the authors calculated the women’s BMIs using this self-reported data from two sources. This is a case of data being used for medical research that wasn’t designed to be accurate for such purposes, which lends a cautionary note.

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. About 60% of eligible pregnant women in the Danish National Birth Cohort during 1998-2001 participated from their first prenatal visit and were followed through their pregnancies. The authors looked for correlations between the women’s characteristics and the subsequent 679 fetal deaths.

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.

They did secondary analyses breaking down the data according to gestation in weeks and BMIs, trying to find a correlation. Only then did they find a correlation that appeared notable: pregnancies over 40 weeks and BMIs>30 (HR=4.6), however it wasn’t statistically significant and was based on only 4 babies. As the authors admitted, “the limited number of cases may not justify such detailed analysis.” They concluded that the small number of stillbirths reduced their ability to determine relationships.

The Danish cohort study authors also cautioned about misinterpreting findings from other studies seeming to find a modest increased risk of stillbirths in obese women. The choice of the reference group can skew findings, they said. For example, they noted a high risk of late spontaneous abortions among underweight women, which can explain their subsequent lower risk of stillbirths seen in stats. They also said that the retrospective collected information (recall data) relied on in other studies miss important confounding factors. Associations between obesity and stillbirths are not necessarily causally related, they concluded, and any weight loss advice for obese women who want to become pregnant would be offered “in a context where causal inference is still speculative.”

The bottom line is that the evidence, even in this review, doesn’t support the scares being directed at fat women about stillborn babies and other horrors in the news.

Take a deep breath and arm women

It’s important to remember, that stillbirth rates across developed countries are low. And most importantly, there is no intrinsic risk of stillbirths associated with being fat. Such a belief has been disproven in large studies which have demonstrated that even the most “extremely obese” women have the same stillbirth rates as “normal” weight women. Researchers around the world have identified the most critical underlying reasons for disparities when women and babies die in childbirth: social and economic deprivations and poor prenatal care and medical interventions.

Blaming patients does nothing towards effectively saving the lives of mothers and babies. And it risks alienating women from seeking care. Women need to know that compassionate medical care will be provided by professionals who aren’t looking to blame them for their fat.

Mothers, please keep your babies and yourselves safe. Media literacy has never been more important to help protect yourself from being needlessly frightened or making decisions that could jeopardize your health or your baby’s or to not seek life-saving medical care. The soundest, healthiest media literacy maxim for all of us today is that news is advertising copy. News is marketing. News may be entertaining. But news is rarely sound medical or scientific information.

For your health and wellbeing, a few exceptions to this rule simply don’t negate this as a helpful axiom anymore.

If it seems like the media scares about fat pregnant women have been incessant lately, you would be right. We’ll likely be seeing even more of this as the Institute of Medicine has been commissioned to re-examine pregnancy weight guidelines and develop consumer messaging and public health strategies to reduce obesity and weight gain. This 22-month initiative has been previously reviewed, along with the reasons why the guidelines are as they are today. The IOM is expected to release its report next summer.

Last week, on June 5th, this initiative held its meeting on the “Implications of weight gain for pregnancy outcomes.”

To find information we can trust, we have to go to the original source; carefully examine the research to determine if it’s a fair test; ensure that its findings are biologically plausible, have been replicated and are supported in a body of evidence; and then, it might be worthy of note. Of course, sound science moves slowly and methodically, and media isn’t going to wait for all of that — there would be lots of dead air space, blank pages and empty advertising coffers. So, instead, we get mostly junk.

© 2008 Sandy Szwarc

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