At what level do pregnancy complications begin?
The results from a new study show that risk increased in women with an early HbA1c of at least 5.9% regardless of a gestational diabetes diagnosis later in pregnancy.
Risk of obstetric complications increases linearly with rising maternal glycemia. Testing HbA1c is an effective option to detect hyperglycemia, but its association with adverse pregnancy outcomes remains unclear. Emerging data sustains that an early HbA1c≥5.9% could act as a pregnancy risk marker.
The purpose of the study was to determine, in a multi-ethnic cohort, whether an early ≥5.9% HbA1c could be useful to identify women without diabetes mellitus at increased pregnancy risk. Primary outcome was macrosomia. Secondary outcomes were pre-eclampsia, preterm birth and Caesarean section rate.
1,228 pregnancies were included for outcome analysis. Women with HbA1c≥5.9% (n= 48) showed a higher rate of macrosomia (16.7% vs. 5.9%,p= 0.008) and a tendency towards a higher rate of preeclampsia (9.32% vs. 3.9% ,p= 0.092). There were no significant differences in other pregnancy outcomes. After adjusting for potential confounders, an HbA1c≥5.9% was independently associated with a three-fold increased risk of macrosomia (p= 0.028) and preeclampsia (p= 0.036).
They evaluated data on 1,228 pregnant women from April 2013 to September 2015 to determine whether an early HbA1c of at least 5.9% can identify women at increased risk for adverse pregnancy outcomes.
Participants were screened for gestational diabetes at 24 to 28 weeks’ gestation, and HbA1c measurement was added to first antenatal blood tests. The primary outcome of the study was macrosomia, and secondary outcomes included rates of preeclampsia, preterm birth and caesarean section.
Compared with participants with an HbA1c less than 5.9% (n = 48), participants with an HbA1c of at least 5.9% (n = 1,180) were more often members of ethnic minorities, had higher pre-pregnancy BMI, were more likely to have anemia and microcytosis, and were more likely to be diagnosed with gestational diabetes.
The rate of macrosomia was increased nearly threefold in participants with HbA1c of at least 5.9% compared with participants with HbA1c less than 5.9%; there also was an increased tendency toward preeclampsia. The rates of preterm birth and caesarean section did not differ significantly between the two groups.
Among participants with HbA1c of at least 5.9%, 22 were diagnosed and treated for gestational diabetes.
From the results of the study it was concluded that, in a multiethnic population, an early HbA1c ≥5.9% measurement identifies women at high risk for poorer pregnancy outcomes independently of GDM diagnosis later in pregnancy. Further studies are required to establish cutoff points adapted to each ethnic group and to assess whether early detection and treatment are of benefit.
In an earlier study published by the American Diabetes Association (Diabetes Care, 2014) they demonstrated that a simple A1c blood test can uncover hidden type 2 diabetes in expectant mothers. The study found that the A1c test can accurately detect undiagnosed type 2 and prediabetes in pregnant women.
The hemoglobin A1c done early in pregnancy may be a convenient and effective way to identify women with pre-existing type 2 diabetes or who are at greater risk of worse pregnancy outcomes.
In this study, researchers examined the use of an A1c measurement done during the first trimester as a screening tool for pre-existing diabetes. The test was performed on more than 16,000 pregnant women and compared with the results of a 2-hour oral glucose tolerance test (OGTT), which is performed after an overnight fast, and is the gold standard diagnostic test for type 2 diabetes.
The study found that the hemoglobin A1c test was able to identify all the women with pre-existing type 2 diabetes when an A1c cutoff point of 5.9 percent was used, said Dr. Florence Brown from Joslin Diabetes Center in Boston. “In addition, even if women did not have pre-existing diabetes, the A1c cutoff point of 5.9 was able to identify a population of women at greater risk for adverse pregnancy outcomes, including some women with gestational diabetes.”
This is an important finding because 5.9 percent is considerably lower than the value of 6.5 percent currently used to diagnose patients with type 2 diabetes who are not pregnant, she adds. The 6.5 percent threshold would have missed almost half of these women and is therefore too high for screening purposes, the study authors conclude.
This study also found that an early pregnancy A1c of 5.9 percent to 6.4 percent was associated with a greater risk of worse pregnancy outcomes, including birth defects, preeclampsia and perinatal death.
Given that the prevalence of type 2 diabetes is increasing, the A1c test done as early as possible could identify women at high risk and improve pregnancy outcomes. “This study supports the use of an A1c test in the first trimester and ideally with the first prenatal visit as one possible screen for pregnant women,” said Dr. Brown.
Practice Pearls:
- A1c test in the first trimester and ideally with the first prenatal visit is one possible screen for pregnant women.
- An A1c test done as early as possible could identify women at high risk and improve pregnancy outcomes.
- All pregnant women should undergo screening for diabetes and prediabetes at initial appointment and also later in their pregnancy.
Mañé L, et al. J Clin Endocrinol Metab. 2016;doi:10.1210/jc.2016-2581.
Feature
Diabetes Diet 
I’m delighted that The BMJ has stood by this article and decided against retraction. Two outside reviewers judged that the criticisms of the piece did not merit its retraction, and in the end, the corrections made by The BMJ do not, in my view, materially undermine any of the article’s key claims. This article therefore stands as one of the most serious ever, peer-reviewed critiques of the expert report for the US Dietary Guidelines for Americans (DGAs).
The importance of the DGAs, and therefore of this article, should not be understated (and indeed was recognized by many in the mainstream media when the article was published). The DGAs have long been considered the “gold standard,” informing the US food supply, military rations, US government feeding assistance programs such as the National School Lunch Program which are, altogether, consumed by 1 in 4 Americans each month, as well as the guidelines of professional societies and governments around the world, and eating habits generally.
Yet rates of obesity began to shoot upwards in the very year, 1980, that the DGAs were introduced, and the diabetes epidemic began soon thereafter. A critically important yet little understood issue is why the DGAs have failed, so spectacularly, to safeguard health from the very nutrition-related diseases that they were supposed to prevent.
In documenting fundamental failures in the science behind the DGAs, this article offers new insights; It establishes that a vast amount of nutrition science funded by the National Institutes of Health and other governments worldwide has, for decades, been systematically ignored or dismissed, and that therefore, that the DGAs are not based on a comprehensive reviews of the most rigorous science. Incorporating this long-ignored relevant science would likely lead to fundamentally different DGAs and could very well be an important step in infusing them with the power to better fight the nutrition-related diseases.
A fundamental question is why 170+ researchers (including all the 2015 DGA committee members, or “DGAC”), organized by the advocacy group, the Center for Science in the Public Interest (CSPI), would sign a letter asking for retraction. After all, in the weeks following publication, any person had the opportunity to submit a “Rapid Response” to the article, and both CSPI and the DGAC did so, alleging many errors. I responded to them all in my Rapid Response. This is the normal post-publication process.
Yet after all this, CSPI returned for a second round of criticisms, recycling two of the issues (CSPI points #3 and #10) that I had already addressed in my Rapid Response (and which had required no correction), adding another 9 (one of which, #4, contained no challenge of fact), and demanding that based on these alleged errors, the article be retracted. CSPI then circulated this letter widely to colleagues and asked them to sign on.
This lack of substance in the retraction effort seems to point to the reality that it was first and foremost an act of advocacy—a heavy handed attempt to silence arguments with which CSPI, a longtime supporter of the Dietary Guidelines and its allies disagree.[ footnote 1] And this applies not just to the retraction letter but to other CSPI efforts to stifle alternative viewpoints. Earlier this year, for example, I was dis-invited from the National Food Policy Conference after CSPI, together with the USDA official in charge of the Dietary Guidelines, threatened to withdraw if I were included, details of which are reported here and which a Spiked columnist called an act of “censorship.”
It’s important to note that I am not the only person disturbed by the lack of rigorous science underpinning our dietary guidelines. Numerous scientists around the world have expressed concern about the science. And indeed, this consternation is shared by no less than the US Congress, which held a hearing on Oct 7, 2015 to address its serious doubts about the DGAs. Such was this concern that last year that Congress mandated the first-ever major peer-review of the DGAs, by the National Academy of Medicine. Congress appropriated $1 million for this review, and it additionally stipulated that all members of the 2015 DGA committee recuse themselves from the process.
What is the dangerous information challenging the DGAs that cannot be heard on a conference panel nor published in a peer-reviewed journal?
The major findings of this article are that:
1. The DGAC’s finding that the evidence of a “strong” link between saturated fats and heart disease was not clearly supported by the evidence cited. (Note that as of last year, the Heart and Stroke Foundation of Canada no longer limits saturated fats. Note, also, that Frank Hu, the Harvard epidemiologist in charge of the DGAC review on saturated fats, was an energetic promoter of the retraction letter against my article that critiqued his review, according to emails obtained through FOIA requests);
2. Successive DGA committees have for decades ignored or dismissed a large body of rigorous (randomized controlled trial) literature on the low-fat diet, on more than 50K subjects, collectively finding that this diet is ineffective for fighting obesity, diabetes, heart disease or any kind of cancer;
3. Although the DGAs have for decades recommended avoiding saturated fats and cholesterol to prevent heart disease, no DGA committee has ever directly reviewed the enormous body of rigorous (government-funded, randomized controlled trials) evidence, testing more than 25,000 people, on this hypothesis. Many reviews of this data have concluded that saturated fats have no effect on cardiovascular mortality;
4. The DGAC ignored a large body of scientific literature on low-carbohydrate diets (including several “long term” trials, of 2-years duration) demonstrating that these diets are safe and highly effective for combatting obesity, diabetes, and heart disease;
5. The Nutrition Evidence Library (NEL) set up by USDA to do systematic reviews of the science did not meet its own standards for its review of saturated fats in 2010;
6. Although the DGAC is supposed to consult the NEL to conduct systematic reviews of the science, the 2015 DGAC did so for only 67% of the questions that required systematic reviews;
7. For a number of key reviews, the 2015 DGAC relied on work done in part by the American Heart Association and the American College of Cardiology, which are private associations supported by industry and therefore have a potential conflict of interest;
8. The DGAs, for the first time, introduce the “vegetarian diet” as one of its three, recommended “Dietary Patterns,” yet a NEL review of this diet concluded that the evidence for this its disease-fighting powers is only “limited,” which is the lowest rank of evidence assigned for available data;
9. The DGA’s three recommended “Dietary Patterns” are supported by only limited evidence. The NEL review found only “limited” or “insufficient” evidence that the diets could combat diabetes and only “moderate” evidence that the diets can help people lose weight. The report also gave a strong rating to the evidence that its recommended diets can fight heart disease, yet here, several studies are presented, but none unambiguously supports this claim. In conclusion, the quantity of recommended diets are supported by a small quantity of rigorous evidence that only marginally supports claims that these diets can promote better health than alternatives;
10. The DGA process does not require committee members to disclose conflicts of interest and also that, for the first time, the committee chair came not from a university but from industry;
11. The 2015 DGAC conducted a number of reviews in ways that were not systematic. This allowed for the potential introduction of bias (e.g., cherry picking of the evidence).
This last claim, on the systematic nature of the DGAC reviews, is the subject of the corrections published in The BMJ this week, and refer to CSPI points #1, #2, #7, and #8 (two of which are statements in the text and two of which are in the supporting tables). I am grateful to have had the opportunity to work with The BMJ on developing this notice.
The BMJ has placed a word limit on my response. For the rest of this comment, please see: http://thebigfatsurprise.com/comment-bmj-correction-notice/
Footnote 1
CSPI has fought for decades to eliminate saturated fats from the American food supply (so much so, that throughout the late 1980s, CSPI advocated for replacing saturated fats with trans fats and succeeded in driving up consumption of trans fats to historic levels, as described in The Big Fat Surprise, pp.227-228). CSPI has also long advocated for shifting away from animal foods containing saturated fats, towards a plant-based diet based on grains and industrial vegetable oils. The researchers who joined CSPI in signing the letter are largely adherents to this view; many have participated in generating the science that has been used to support the hypothesis that fat and cholesterol cause heart disease, and it is upon this hypothesis that the Guidelines have been based.
Competing interests: I have read and understood BMJ policy on declaration of interests and declare that I am the author of The Big Fat Surprise (Simon & Schuster, 2014), on the history, science, and politics of dietary fat recommendations. I have received modest honorariums for presenting my research findings presented in the book to a variety of groups related to the medical, restaurant, financial, meat, and dairy industries. I am also a board member of a non-profit organization, the Nutrition Coalition, dedicated to ensuring that nutrition policy is based on rigorous science.