Relationship between artificially sweetened and sugar-sweetened cola beverage consumption during pregnancy and preterm delivery in a multi-ethnic cohort: analysis of the Born in Bradford cohort study

Abstract

The aim of this study was to investigate the relationship between the intake of sugar-sweetened (SS) and artificially sweetened (AS) cola beverages during pregnancy and the risk of preterm delivery (PTD). At baseline (2007–2010), 8914 pregnant women were recruited to the Born in Bradford birth cohort study at 24–28 weeks of pregnancy. Women completed a questionnaire describing their health and lifestyle behaviours, including their consumption of AS and SS cola beverages reported as cups per day, which were then linked to maternity records. The relationship between SS and AS cola beverage consumption was examined using logistic regression analyses. No relationship was observed between daily AS cola beverage consumption and PTD. Women who drank four cups per day of SS cola beverages had higher odds of a PTD when compared with women who did not consume these beverages daily. We conclude that high daily consumption of SS cola beverages during pregnancy is associated with increases in the rate of PTD.

Introduction

The consumption of sugar-sweetened (SS) beverages has been shown to be an increasing contributor to total energy intake.1 Artificially sweetened (AS) drinks have been proposed as a healthier alternative to SS beverages, although there is conflicting evidence as to whether their consumption contributes to weight loss.2 In the United Kingdom, carbonated soft drinks constitute over half of all soft drinks consumed with over 6000 million litres purchased in 2011 and of these soft drinks, 62% are SS.3 Over half, 53%, of carbonated soft drinks consumed in the United Kingdom are cola beverages.3

There is some evidence of a link between the consumption of both AS and SS by mothers during pregnancy and increased odds of preterm birth, although only the relationship between AS beverages and preterm birth was consistent across both studies.4, 5 Being born preterm, delivery before 37 weeks gestation, is associated with perinatal mortality and morbidity.6, 7

We hypothesised that the same associations observed between preterm birth and AS and SS beverage intake would be evident only when cola beverage intake was evaluated.

Subjects and methods

Population and study design

Born in Bradford (BiB) is a longitudinal multi-ethnic birth cohort study aiming to examine the impact of environmental, psychological and genetic factors on maternal and child health and well-being.8 Bradford is a city in the North of England with high levels of socio-economic deprivation and ethnic diversity. Pregnant women were recruited at the Bradford Royal Infirmary at 26–28 weeks of gestation at which time a baseline questionnaire was completed.8 Ethical approval for the study was granted by Bradford Research Ethics Committee (ref no. 07/H1302/112).

Assessment of beverage intake

At baseline, we captured pregnant women’s daily self-reported consumption of SS and AS cola over the previous 4-week period. Consumption was categorised as none, one, two, three or four or more cups per day, with each cup measuring 200 ml.

Preterm delivery

Preterm delivery (PTD) was defined as birth before gestational week 37+0. Gestational length was defined as the length of gestation after amenorrhoea, which was based on last menstrual period date confirmed by dating ultrasound conducted at 12 weeks of gestation. If there were less than 7 days difference between these two dates, the last menstrual period date was used for the estimated date of delivery, whereas if there were a greater than 7 days difference then the ultrasound dating scan was used to assign the estimated date of delivery.

Covariate adjustment

All models were adjusted for the following confounders known to be associated with PTD. These were maternal age, parity, maternal body mass index at booking, marital and partnership status (categorised as married and living with a partner, not married living with a partner and not living with a partner), smoking status, maternal education (categorised as <5 general certificates of secondary education (GCSEs) and >5 general certificates of secondary education (GCSEs), A level equivalent, higher than A level equivalent, other or none/foreign unknown) and ethnicity (categorised as White British, Pakistani, Other South Asian and Other). Births were spontaneous if they were normal vaginal deliveries or medically induced if they were delivered using medical or surgical induction or by caesarean section. We removed data from women who had more than one study enrolment throughout the study period, avoiding the use of multiple dependent observations and excluded women with pre-existing diabetes and hypertension.

Statistical methods

Statistical analyses were conducted using Stata SE 12.1 (StataCorp LP, College Station, TX, USA). Descriptive analyses were conducted using proportions for categorical variables and means and s.d. for continuous variables. Comparison of baseline characteristics between different AS and SS cola beverage consumption groups was undertaken using χ2-tests for categorical variables and linear regression to test for trends in continuous variables.

Univariate and multivariate logistic regression analyses were used to model the association between AS and SS cola beverage intake and PTD. All regression analyses were performed crudely and adjusted for the covariates mentioned above.

Results

The baseline characteristics of 8191 eligible pregnant women were examined (Table 1). Daily consumption of any cola beverages throughout pregnancy was low with 5% reporting daily consumption of AS cola and 14% consuming SS cola beverages daily, although data on cola consumption was missing for 4% of participants.

Table 1 Baseline characteristics of mothers stratified by beverage consumption

Younger pregnant women were more likely to consume SS cola beverages, whereas no association with age was seen with AS cola beverages. Parity was not shown to be associated with consumption of either AS or SS beverages. Higher consumers of both AS and SS cola beverages were more likely to have lower levels of education, be less likely to be married or living with a partner, be smokers and be of White British ethnicity, and have higher body mass indexes compared with women who consumed lower levels or did not consume these beverages.

Logistic regression was used to investigate the relationship between frequency of daily beverage cola consumption and preterm birth (Table 2). AS cola beverages consumption was not shown to be associated with an increased risk of PTD irrespective of the amount of AS cola beverages consumed per day.

Table 2 Associations between the intake of AS and SS cola beverages during pregnancy and rates of PTD, <37 completed gestational weeks

Pregnant women who consumed >4 cups per day of beverages had an increased odds of PTD compared with non-consumers of SS cola beverages, odds ratio 1.81 (95% confidence interval (CI) 1.03, 3.18), below this amount no increase in risk was observed. Tests for trend of both AS and SS cola beverage consumption showed no dose relationship.

Discussion

Main findings

Consumption of AS cola beverages were not associated with preterm birth. Consumption of four cups or more of SS cola beverages per day during pregnancy was shown to be associated with an increased risk of PTD compared with women who consumed none.

Findings in relation to other literature

Our findings of an increased risk of PTD with higher consumption of SS cola beverages are consistent with previous research that had looked at consumption of all types of SS beverages.5 In contrast to previous studies conducted in Denmark and Norway,4, 5 we did not find an association between AS beverages and PTD, although we were possibly underpowered to find an association should it exist, as our analyses were limited to the investigation of AS cola beverages only. Wherever possible, the same confounding variables were chosen that had been used in previous research, although we were unable to control for previous PTD as this variable was not available.4, 5 In common with previous findings, our work has also shown that increased intake of AS and SS cola beverages is socially patterned with socio-economic markers such as lower education and higher proportions of women being not married and not living with a partner, as well as in those women who smoked during pregnancy.4, 5

Strengths and weaknesses

The strength of this study was that it was conducted using prospectively collected data in a large multi-ethnic sample, and missing data on intake of these cola beverages was rare at only 4% minimising the potential for non-response bias. The main weaknesses of this study is that we have only been able to investigate the relationship with cola soft drink beverages and PTD, as we did not undertake a full analysis of diet during pregnancy and we were adjusted for previous preterm birth, a known risk factor for subsequent preterm birth. Despite this, our findings of a positive relationship between SS cola beverage intake of >4 servings per day and preterm birth were consistent with the findings of Englund-Ögge et al.5

Conclusions

The results of these analyses demonstrate that high levels of SS cola beverage consumption during pregnancy are associated with increases in rates of PTD.

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Acknowledgements

BiB was only possible because of the enthusiasm and commitment of the children and parents in BiB. We are grateful to all the participants, health professionals and researchers who have made BiB happen. This work was funded by the Institute for European expertise in physiology and also by an National Institute for Health Research (NIHR) Collaborations for Leadership in Applied Health Research and Care (CLAHRC) implementation grant (CLAHRC implementation grant (KRD/012/001/006)).

Disclaimer

The funders had no role in the design or interpretation of the results of this study. This paper presents independent research commissioned by the NIHR under the CLAHRC programme for Leeds, York and Bradford. The views expressed are those of the author(s) and not necessarily those of the National Health Service, the NIHR or the Department of Health.

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Correspondence to E S Petherick.

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Petherick, E., Goran, M. & Wright, J. Relationship between artificially sweetened and sugar-sweetened cola beverage consumption during pregnancy and preterm delivery in a multi-ethnic cohort: analysis of the Born in Bradford cohort study. Eur J Clin Nutr 68, 404–407 (2014). https://doi.org/10.1038/ejcn.2013.267

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Keywords

  • preterm birth
  • cola beverages
  • maternal health
  • maternal nutrition

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