Strengths and Limitations
To our knowledge this is the first published study on the association
between timing of IOL and maternal and newborn outcomes in low-risk
pregnancies in Sri Lanka. It is also the first study from a setting with
limited resources reporting on the use of a prospective
individual-patient database to analyse practices and outcomes of
IOL.24 This study contributes to current international
and local debate on the appropriateness of IOL near term. These study
findings are extremely relevant locally both
for clinicians, researchers and
policy makers, as IOL at 40 GW is a common practice in Sri Lanka and has
a significant economic impact on
the health system and healthcare resources.
We acknowledge some limitations of this study. As an observational
study, we could only assess associations between IOL and birth outcomes
and not causation. Generalizability of study results may be limited by
the characteristics of the local context and population in this single
centre study. Larger sample sizes are required to detect significant
differences in rare adverse events including stillbirth or maternal or
perinatal death. Although gestational age was mostly determined by
ultrasound examination, for 12% of the included women gestational age
was estimated by menstrual dating.
Socio-cultural background and women’s empowerment may have affected both
requests for induction and the type of care offered by physicians.
Specifically, early induction (IOL at 40 GW) occurred more often in
women with a high level of education. Unmarried women, still subjected
to social stigma in Sri Lanka,29 were significantly
more represented in the group undergoing IOL at 41 GW. Thus, numbers of
CS and neonatal complications may have been influenced by socio-economic
status. Other authors have described similar results, where unmarried
women could have limited access to care29 while higher
social status or economic condition is related to an increasing
medicalization of birth.30,31 However, in our study,
since these imbalances among groups affect results in different
directions, there may be limited risk of bias.
Though results were corrected for confounding, we cannot exclude that
induced women may have differed on characteristics not captured or not
reported in the data collection form (such as unreported small for
gestation foetuses, mild oligohydramnios, etc.). We were not able to
explore specific practices related to IOL (such as safe use of
uterotonics, appropriate maternal-foetal monitoring or CS indications),
therefore we cannot exclude a difference among the groups for these
variables. We had no information on the level of women’s participation
in the decision process during labour care, nor specific choices,
inclinations or skills of operators which may have had a substantial
role in the differences observed.27, 32-34 Notably,
most of the evidence that we actually rely on may have some of these
biases. Observational studies may not capture these aspects of care,
while RCT, even though controlling these with randomization, may suffer
from study effect.
Finally, another limitation related to the database is the absence of
timing for risk factor onset. Hence it was impossible to differentiate
between high-risk pregnancy (with risk factors before 40+0 GW) and low
risk women at 40+0 GW that developed complications due to prolonged
pregnancy (after 40+0 GW). A sensitivity analysis was performed to
assess this limitation and results showed that it did not affect the
overall findings.