Birth Interval

Birth intervals of 24–35 months are associated with the lowest perinatal mortality risk, consistent with evidence that moderate spacing is optimal in low- and middle-income settings. The primary biological mechanism linking short birth intervals to perinatal mortality is maternal depletion syndrome, whereby rapid successive pregnancies exhaust nutritional reserves and recovery capacity. The proposed mechanism for elevated risk with long intervals is physiological regression, whereby the maternal reproductive system may lose adaptive capacity after extended periods without pregnancy, increasing susceptibility to pre-eclampsia. Birth intervals shorter than 12 months carry the highest perinatal mortality risk, with an adjusted odds ratio of 4.07. First births carry a 3.55-fold increase in perinatal mortality risk and are analytically distinct from interval-based groupings. Long birth intervals of 60 months or more are associated with nearly threefold higher perinatal mortality risk, with an AOR of 2.94. Short birth intervals are also associated with increased likelihood of infection transmission from mother to fetus or newborn.