Strengths and limitations
This study used data from a large prospective birth cohort, which
minimises selection bias. However, following exclusions and
categorisation of data, sample sizes were reduced. Although this study
had a large sample size of 3514 White British women and 4310 South Asian
women, the numbers of women with early pregnancy obesity were much
smaller (903 and 1312 respectively). This study applied the
Asian-specific BMI criteria as well as carrying out a secondary analysis
using general population BMI criteria, which adds to the pregnancy
evidence-base for South Asian women. We also used mother’s booking BMI
which is measured in early pregnancy rather than self-reported
pre-pregnancy weight and height. This approach reduces self-reporting
bias since self-reported BMI tends to be under-estimated and provides a
more accurate measure of BMI.22
The South Asian ethnic group encompassed Pakistani, Indian and
Bangladesh women which may introduce heterogeneity. Pakistani women have
higher rates of obesity compared to Indian and Bangladeshi
women.23 Rates of depression are also different
between these sub-groups, with Indians showing higher rates (61%)
compared with Pakistani and Bangladeshi people
(55%).24 Nevertheless, 88% of the included South
Asian group were Pakistani, therefore, inclusion of women from India and
Bangladesh may not have resulted in much bias.
The use of the GHQ in a South Asian sample comes with limitations as
screening instruments may perform differently in different populations
due to cultural and social differences.25 This is
especially important to consider when assessing differences between
populations as was the case in this study. In a study examining the
psychometric properties of the subscales of the GHQ in a multi-ethnic
maternal sample from the BiB cohort,25 results showed
that there was variation in the concepts measured by the GHQ between
groups of different language and ethnic heritage. This may be due to the
artefacts of translation and administration bias. The meaning of
underlying concepts for some of the GHQ items differ according to
language of administration.25 Nevertheless, these
issues of subjectivity and translations are found within most
measurement tools, hence, more studies should be carried out in South
Asian women using measurement tools such as the Edinburgh Postnatal
Depression Scale (EPDS) which has validated Urdu26 and
Bengali27 versions.