Multiple births mortality by maternal age at birth: A within-family analysis of Demographic and Health Survey data on 42 low-income countries

Background: Existing evidence suggests that, in contrast to singletons, multiple-birth-children experience lower mortality with advanced maternal age. It is currently unknown if the association is confounded by unobserved, time-invariant maternal characteristics, and how the association develops across the full distribution of maternal age as well as in low-income countries, where infant mortality rates are amongst the highest globally.

Methods: Using the Demographic Health Surveys data of over 6 million live births reported from 42 low-income countries, we applied mother fixed-effects in linear probability models with and without parity.

Results: The probability of dying within the 1st year of life (as well as the 1st month of life) for multiple-birth-children is higher when mothers are younger. Compared to the maternal age at 24-25, the probability of dying within a year increases the most (0.14 [0.13, 0.15]) if maternal age below 18 and declines by around 0.01 until a mother reaches her late 30s. The overall pattern was robust to the addition of parity to the model and estimation without mother fixed-effects. Similar patterns hold in Southern Asia and sub-Saharan Africa, and across different developmental settings.

Conclusions: Our results highlight the lower mortality of children from multiple births when mothers in the 30s compared to when mothers are in the mid-20s or younger. Unlike previous findings, the lower mortality associated with advanced maternal age is visible from the mid-20s