Discussion
Main findings
Our study found that both increased duration and intensity of
breastfeeding following a GDM-affected pregnancy were associated with a
reduction in the risk of developing GDM in a subsequent pregnancy.
Furthermore, breastfeeding duration and intensity influenced the glucose
levels of the OGTT performed during the subsequent pregnancy.
There is a growing body of evidence demonstrating the association
between breastfeeding and a reduction in type 2
diabetes.13, 20, 21 Stuebe (2015) hypothesized that
early, high intensity lactation may be crucial in the ‘resetting’ of an
endocrine balance from an insulin-resistant state in pregnancy, and,
without the lactation-mediated reset, there may be long-term
cardiometabolic health consequences.22 Studies have
demonstrated that with a greater lifetime-years of maternal
breastfeeding there is a corresponding risk reduction for type 2
diabetes.12, 23 Research using data from the Nurses’
Health Study found that for every extra lifetime-year of breastfeeding,
there was a 15% reduction in the risk of type 2 diabetes for women who
had a pregnancy in the last 15 years.20
In a study that included both post-GDM (n = 300) and non-GDM (n = 220)
women, O’Reilly et al. (2011) found that hyperglycemia was more frequent
at the postpartum OGTT in women who were not breastfeeding compared to
women who were, with breastfeeding reducing the incidence of postpartum
hyperglycemia by 60%.24 The SWIFT study was the first
prospective investigation of breastfeeding intensity and
hyperglycemia.25 It found an association between
higher intensity breastfeeding and improved postpartum OGTT levels. As
early as 6–9 weeks postpartum, a greater intensity of breastfeeding in
women with GDM resulted in a lower mean fasting plasma glucose level as
measured at their postpartum OGTT and a dose response to improved
homeostasis model assessment (HOMA-IR). The SWIFT study also
demonstrated that there was a dose-protective response of intensity and
length of breastfeeding for type 2 diabetes risk two years after the GDM
pregnancy.25
A lower HbA1c is associated with greater lengths of breastfeeding
postpartum.13 There is also evidence that
breastfeeding improves insulin sensitivity, with women who breastfed at
high intensity having a lower HOMA-IR at 6–10 weeks’ postpartum, though
this may only be evident in obese women.26
Although there are benefits of breastfeeding for women who have had GDM,
evidence suggests that these women have greater difficulty breastfeeding
than unaffected women.27, 28 Women with GDM have more
issues establishing breastfeeding, experience delayed lactogenesis and
breastfeed for a shorter duration than other women.29Oza-Frank et al. (2017) found that women with GDM experienced practices
in hospital that are known to negatively impact on long-term
breastfeeding.30 For example, they were less likely to
breastfeed in the first hour after birth and it was more likely that
their baby received formula in hospital than women without GDM. The
importance of breastfeeding for women with GDM therefore requires
greater understanding for effective, targeted lactation support. Careful
consideration needs to be given to protocols whereby babies of women
with gestational diabetes are routinely admitted to special care
nurseries as this may negatively impact breastfeeding
success.30
Breastfeeding intensity and duration can be improved through appropriate
education and consistent advice that ideally includes both antenatal and
postnatal care.31 Novel engagement with the use of
text-based support has been trialled, with one study suggesting the best
predictor for exclusive breastfeeding was strong engagement in the first
two weeks postpartum utilising two-way lactation consultant texting
support.32 Stuebe et al. (2016) found GDM women were
less likely to stop breastfeeding or introduce formula (adjusted HR
0.50, 95% CI 0.34–0.72) at six weeks when provided with a pre- and
postnatal lifestyle intervention program that included breastfeeding
text-based support.33 A recent (2017) Cochrane review
found that lactation support for women improved breastfeeding intensity
for up to six months.34
Provision of comprehensive lifestyle and breastfeeding support for GDM
women requires investment in additional staff time and resources.
However, our study and others have demonstrated that optimal
breastfeeding for women with a history of a GDM pregnancy reduces the
risk of the mother developing type 2 diabetes and other cardiometabolic
disorders. A reduction in hyperglycemia in a subsequent pregnancy also
negates some of the maternal and fetal risks associated with GDM. The
savings from this are likely to offset the investment in the provision
of breastfeeding support. It is a financially judicious use of health
resources to support early prevention for cardiometabolic disease and a
unique opportunity to engage women in health intervention programs that
include breastfeeding support during pregnancy and the postpartum
period.
We are not aware of any published methods for the routine assessment of
breastfeeding intensity. This is important as duration of breastfeeding
by itself does not necessarily reflect early breastfeeding issues. Low
intensity breastfeeding may occur early postpartum, however a small
percentage of mothers will persist despite extreme difficulties (Table
2). Women who breastfeed more successfully with greater intensity tend
to breastfeed for longer.35 The BLISS check is
therefore a novel means of assessing breastfeeding intensity through a
maternal recall questionnaire. Evaluation of previous breastfeeding is
an important component of the pregnancy and postpartum evaluation, and
this can easily be established as a routine tool for use by clinicians.
The findings of our study suggest that the BLISS check score may be a
useful clinical tool.
We are continuing to validate the BLISS check in a larger cohort for
antenatal lactation counselling referral purposes and research. It is
important to work towards standardizing the assessment of breastfeeding
intensity in a manner that is clinically useful and capable of informing
both care and research. Defining and standardizing breastfeeding
terminology for both clinical and research purposes will assist with
comparison of data and patient management.36
Strengths and limitations
The high participation rate of women gave our study strength and reduced
potential recruitment bias. This suggests that women are interested in
breastfeeding and are keen to discuss their breastfeeding history and
associated problems. This also suggests the need for more antenatal
breastfeeding support that provides an appropriate clinical avenue for
breastfeeding counselling and information. Ethnic diversity is an
additional strength of our study and informs the capacity to extrapolate
the results to other populations.
The major weakness of our study is potential recall bias. In the
literature, however, maternal recall of breastfeeding history has been
validated as a reliable method to determine infant feeding
history.37, 38 In a Norwegian study, recall of
duration of breastfeeding was found to be accurate after 20 years with a
median over-estimation of only two weeks.38 The recall
bias in our BLIiNG study would be less, as all participants had only one
previous pregnancy and feeding details to remember. The same recall
limitation would exist for both GDM and non-GDM groups and the mean time
between births was three years for both groups.
Interpretation
There is concern about the high incidence of GDM and its recurrence.
Much of the focus amongst women who have had GDM is to reduce obesity
and improve lifestyle in between pregnancies. However programs aimed at
these risk factors are challenging, resource intensive, and have in
general met with little success.39-41 On the other
hand, breastfeeding is already encouraged, and for the majority of
women, is acceptable, and can be undertaken successfully. Yet this has
largely been neglected in the GDM and diabetes prevention literature.
Conclusions
Our study has demonstrated that a greater intensity of breastfeeding can
improve glycemia and reduce recurrent GDM in pregnant women who have had
a previous GDM-affected pregnancy. Breastfeeding may potentially reduce
future type 2 diabetes and cardiovascular disease risk for the mother,
as well as providing known benefits to the health of the infant. Thus,
the promotion and support of breastfeeding should be routinely
implemented as an important intervention for the prevention of recurrent
GDM and type 2 diabetes.
Disclosure of interest
None declared. All authors declare they have no conflict of interest
which may arise from being named as an author on the manuscript.
Author Contributions
The research idea was conceived by SJM and LW. The study was designed by
SJM, LW, MS, IA, SP and WC. AK performed the statistical analysis, SJM
interpreted the data and wrote the initial drafts with supervision from
WC and DP. Invaluable support was given by IA, WC, DP, LW, MS, SP, VS
and AK for final interpretation of findings, and critical revision of
the article. All authors reviewed and approved the final version of the
article submitted for publication.
Details of ethics
approval
The study was approved by the Western Sydney Local Health District
(WSLHD) Human Research and Ethics Committee (LNR/16/WMEAD/404; 1
February 2017), all participants provided informed consent.
Funding
This research did not receive any specific grant from any
funding agency in the public, commercial or not-for-profit
sector.
Acknowledgments
We acknowledge and appreciate the contribution to the
study of data custodian Monica Hook and the assistance with data
collection by Sarah
Tapp.
Data sharing
No additional data is available in compliance with WSLHD
Human Research and Ethics Committee regulations.
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Table 1 Characteristics of women who were diagnosed with recurrent
gestational diabetes (GDM) in their second pregnancy