Table 1

Significant gaps in knowledge needed to inform recommendations for optimal interpregnancy interval (IPI) recommendations in high-income countries

Knowledge gapDescription
What are the IPI effects after eliminating confounding from between-women comparisons?Few past studies have addressed confounding by matching pregnancies to the same women.1
Can IPI effects be observed later in childhood?No past studies have investigated outcomes beyond the neonatal period, such as hospitalisation in early childhood.
What are the optimal IPIs for which risks are minimised?Although knowledge of harmful IPIs is important, health is optimised by identification of optimal IPIs for which risks are minimised.1
What are the IPI effects for a wide range of outcomes of both the mother and child?The vast majority of studies to date investigate a single endpoint for a single group (mother or child). IPI recommendations require a wide range of health endpoints for both mother and child.
What are the context-specific IPI recommendations?Guideline IPIs are needed for subpopulations ,for example, for women who attempt labour after caesarean birth to avoid uterine rupture,29 and for women after stillbirth due to elevated risk of recurrence or faster maternal recovery. For women at advanced maternal age, delaying child birth even further due to IPI recommendations comes at the cost of competing risks of age-related morbidities.49