DIET QUALITY IN OBESE PREGNANT WOMEN – COULD THERE BE EFFECTS ON GESTATIONAL DIABETES INDEPENDENT OF WEIGHT GAIN?

Background: 
Obesity, excess gestational weight gain and poor diet quality during pregnancy are associated with increased risk of both maternal and fetal complications, including Gestational Diabetes Mellitus (GDM)1. Yet in Australia, standard antenatal care does not include nutritional intervention for obese pregnant women. A gap in the literature was identified with respect to intervention studies to improve diet quality and related health outcomes for obese pregnant women. 

Whilst not statistically significant after adjusting for Asian ethnicity, lower rates of GDM were seen amongst obese pregnant women who received dietetic intervention when compared to the standard care control group (Opie et al 20162 (see table below)). Excess gestational weight gain is commonly believed to be associated with incidence of GDM1. However in our study, gestational weight gain was similar for both groups, posing the question of whether diet quality improvements could be an influential factor in the lower rates of GDM development. 


Aims: To create a Diet Quality Score to explore the degree to which changes in dietary quality occur as a result of a behavioural nutrition intervention, individually tailored for obese pregnant women in early pregnancy.

Methods: A Diet Quality Score was devised in order to produce a single value indicative of diet quality, and hence display dietary quality changes. This score was created based on intake of food group serves, and variety and quality within each food group aligned to Australian Guide to Healthy Eating recommendations for pregnancy3. The Diet Quality Score was scored out of 100; and participants had dietary intake analysed at baseline in early pregnancy (before 20 weeks), and at 36 weeks gestation. 
Results: Food and fluid intake of 43 diet group participants were analysed using the Diet Quality Score at both time points.  
35 women (81%) showed Diet Quality Score improvement from baseline, with an average improvement of 34.0%. 
8 women (19%) had a reduced Diet Quality Score, with an average deterioration of 5.6%.


A Spearman correlation was utilised to assess the strength of the relationship between the Diet Quality score and the Australian Guide to Healthy Eating. The relationship was found to be strong (r=0.816, p value < 0.001). Further validation of the score using a food database (Foodworks4) supported alignment between a high Diet Quality Score and improved macro and micronutrient intake.

Discussion: 
This dietary intervention study found that most obese pregnant women achieved improvements in diet quality, according to the Diet Quality score. Although there was no diet information available for comparison in the control group, there is evidence to suggest that overweight and obese women consume diets of poor quality during pregnancy5,6, 7 and research has suggested that diet quality deteriorates across pregnancy8. 
Whilst acknowledging that weight change during pregnancy influences outcomes, especially when excessive, we speculate that diet quality is of significant importance rather than weight status alone when considering maternal and fetal outcomes.  
The exact aetiology of diet quality influence is not well understood. Poor diet quality could be linked directly with nutritional deficiencies such as folate-deficiency and neural tube defects, or nutrient excesses such as high glycaemic load and carbohydrate intake predisposing to impaired glucose tolerance and GDM.  For the offspring, the nutritional environment during gestation has been thought to further influence health in adulthood through epigenetic factors9. 

We were unable to capture all women for diet analysis at both time points, with 50% of women unavailable in later pregnancy. This is a limitation that prevented any further analysis regarding the relationship between GDM incidence amongst women with improvements or deteriorations in Diet Quality scores.
Furthermore, additional validation and extrapolation of the Diet Quality score to a larger cohort of obese pregnant women is necessary before explicit conclusions can be drawn. However, the positive trend to lower rates of GDM seen in the intervention group, independent of weight change, may suggest an influence from diet quality improvements seen using the Diet Quality Score. The study supports the need for wider research, whilst immediately considering the implementation of routine antenatal nutrition intervention for these high risk obese women.


Reference List:
1.	Ferrara A. Increasing prevalence of gestational diabetes mellitus: a public health perspective. Diabetes Care 2007; 30:S141 – 146.
2.	Opie R.S, Neff M, Tierney A.C. A behavioural nutrition intervention for obese pregnant women – Effects on diet quality, weight gain and the incidence of gestational diabetes.  Aust N Z J Obstet Gynaecol 2016; 56 (4): 364-373.
3.	National Health and Medical Research Council. Healthy eating during your pregnancy. Available from: https://www.eatforhealth.gov.au/sites/default/files/content/The%20Guidelines/n55h_healthy_eating_during_pregnancy.pdf 
4.	Foodworks 8 2012, Xyris Software, High Gate Hill, Qld, Australia.
5.	Pick ME, Edwards M, Moreau D, Ryan EA. Assessment of diet quality in pregnant women using the Healthy Eating Index. J Am Diet Assoc 2005; 105: 240–246.
6.	Tsigga M. Filis V. Hatzopoulou K. Kotzamanidis C. Grammatikopoulou MG. Healthy Eating Index during pregnancy according to pre-gravid and gravid weight status. Public Health Nutrition 2011;14(2):290-296.
7.	Hure A. Young A. Smith R. Collins C. Diet and pregnancy status in Australian women. Public Health Nutrition 2009; 12(6):853-861.
8.	Moran LJ. Sui Z. Cramp CS. Dodd JM. A decrease in diet quality occurs during pregnancy in overweight and obese women which is maintained post-partum. Int J Obes 2013; 37(5):704-1
9.	Hanley B. Dijane J. Fewtrell M. Grynberg A. Hummel S. Junien C. Koletzko B. Lewis S. Renz H. Symonds M. Gros M. Harthoorn L. Mace K. Samuels F. van Der Beek EM. Metabolic imprinting, programming and epigenetics - a review of present priorities and future opportunities. British Journal of Nutrition 2010; 104 (S1): S1-25.


Authorship:
Neff M, Opie RS,

Diet quality in obese pregnant women - Could there be effects on gestational diabetes independent of weight gain?