Conclusions
We have clarified the mediating and interaction effects of gestational
age on labour outcomes for pregnancies complicated by SGA in this causal
mediation analysis. The impact of gestational age on caesarean delivery
without TOL was profound across gestation. Approximately two-third of
all caesareans were performed prelabour. With appropriate counseling,
providers may feel comfortable offering TOL to these patients, optimally
at 39-40 weeks’ gestation.
Rates of caesarean delivery are increased among SGA after a TOL compared
to AGA births at preterm and term gestations, but the effect of
gestational age is different. An interaction between gestational age and
SGA drives the risk at preterm gestations whereas exposure to SGA alone,
likely a consequence of IPD, drives this risk at term. These findings
suggest different strategies are needed to maximize vaginal delivery
rates for SGA pregnancies who undergo TOL, but it is likely that timing
the delivery at term and avoidance of late term gestation would have
positive impact.
Acknowledgments : none
Disclosures of interest : Both authors declare no support from
any organization for the submitted work; no financial relationships with
any organizations that might have an interest in the submitted work in
the previous three years; and no other relationships or activities that
could appear to have influenced the submitted work.