Interpretation
The interpregnancy period is a valuable opportunity to address
complications that have developed during pregnancy and optimise their
health for the next pregnancy and for the rest of the life-course.
Despite recommendations to return to pre-pregnancy weight between 6 and
12 months postpartum, with the goal to achieve a normal
BMI,18 about half of the women in our study had an
increase in BMI during the first two years after delivery instead.
Almost 30% of women who were of normal weight subsequently became
overweight or obese in their next pregnancy, while more than 90% who
were overweight or obese remained the same. Indeed, three-quarters of
women with an initial BMI of 27.5-29.9 kg/m2 had
increased BMI to ≥30 kg/m2 in their second pregnancy
(data not shown). A study conducted among Caucasians also showed similar
findings, in which almost 20% of women of normal weight became
overweight or obese in their next pregnancy, whereas more than 90% of
overweight or obese women maintained their status in the next
pregnancy.19 These alarming numbers highlight the
urgent need to implement intervention strategies including targeted
lifestyle modifications to prevent an increase in BMI during the
interpregnancy period.
The results on interpregnancy BMI gain and the increased risks of
subsequent LGA, GDM and emergency caesarean delivery are consistent with
previous studies.9, 10, 20 These adverse complications
could be due to reduced insulin sensitivity due to interpregnancy weight
gain accompanied by body fat rather than muscle gain, which is common
among Asians.19, 21-24 The heightened risk of
emergency caesarean delivery in women with an initial BMI <23
kg/m2 is consistent with a systematic review and
meta-analysis by Oteng-Ntim et al.21, suggesting that
lean women could be more susceptible to subsequent delivery
complications in response to weight gain between pregnancies. However,
the indications for emergency caesarean delivery were not clear in our
data and should be further examined in future studies. Similarly,
interpregnancy BMI gain has also been associated with an increased risk
of hypertensive disorders9, 25 and
stillbirth10, but we could not analyse these outcomes
due to our limited sample size or incomplete outcome data. In view of
multiple adverse pregnancy outcomes, long-term obesity, and related
health risks in women and their offspring, our study, together with many
others,12, 26-31 calls for a nationwide effort to
break the vicious cycle of interpregnancy weight gain and poor metabolic
health.
We found that offspring of women with BMI loss between their first two
pregnancies were at a higher risk of low birthweight. This is supported
by a study on interpregnancy weight change among women in three
consecutive pregnancies, showing that weight loss was associated with an
increased risk of low placental weight and SGA
births.32 Another study also showed that a decrease in
BMI >1 kg/m2 was associated with low
birthweight (<2500 g).33 This phenomenon
could be explained by insulin sensitivity induced by weight loss,
resulting in less glucose crossing the placenta, which contributed to an
increased risk of small fetal size.21 A meta-analysis
showed that interpregnancy weight loss and SGA was only apparent in
women with initial BMI <25 kg/m2, but not
among those with BMI ≥25 kg/m2.10 In
contrast, we observed that women with BMI ≥23 kg/m2who lost weight during the interpregnancy interval were at a higher risk
of low birthweight and SGA, compared to those with BMI <23
kg/m2 in the first pregnancy. This may be attributed
to the greater weight loss among women who were overweight or obese
within the interpregnancy interval of 1-2 years, compared with women who
were lean (BMI loss 1.9 vs 1.5 kg/m2,
p<0.001). In addition, unlike other studies which showed a
reduction in the risk of adverse pregnancy outcomes among overweight and
obese women who lost weight,10, 19-21 our study did
not find any significant risk reduction among women with BMI ≥23
kg/m2 who lost weight. Despite the current emphasis on
BMI, it represents a crude measure of adiposity and an imperfect
assessment of metabolic health.34 This was highlighted
by a recent study that showed that metabolic health status, rather than
BMI, played a greater role in fecundability.35Therefore, interpregnancy BMI loss may not truly reflect the metabolic
health status of those in our study, which may possibly confound the
positive effects of weight loss in overweight and obese women.
Furthermore, changes in body composition and fat distribution between
pregnancies in these women who were overweight or obese may impact on
subsequent pregnancy outcomes. This points to the need to investigate
the metabolic profile and body composition of women in future studies of
interpregnancy weight change and associated outcomes.
Taken together, maintaining a stable interpregnancy BMI is recommended,
instead of losing weight between pregnancies. Based on the trend of
interpregnancy BMI change, the first two years after delivery likely
represents the best window of opportunity to intervene to return to
pre-pregnancy BMI, regardless of initial weight status. Effective
lifestyle interventions aimed at limiting postpartum weight retention
and maintaining a stable interpregnancy BMI during this window are
crucial to improve perinatal outcomes. Such interventions should ideally
be engaging, grounded by behaviour change theories, and integrate
components of both diet and physical activity.36Recently, Bijlholt et al.37 adopted an electronic
health approach for postpartum women with excessive GWG, resulting in
restrained eating as well as decreased uncontrolled eating and energy
intake. However, there was no change in other behaviours such as
emotional eating, physical activity, and sedentary
time.37 To improve the success of lifestyle
interventions, it is essential to identify additional enablers and
barriers faced by these women. Although Ku et
al. 38 identified potential enablers and
barriers among overweight and obese women trying to conceive, it remains
unclear whether such findings are applicable to women of normal weight.