Mobile phone survey estimates of perinatal mortality in Malawi: A comparison of data from truncated and full pregnancy histories.

objectivesIn many low- and middle-income countries, perinatal mortality estimates are derived retrospectively from periodically conducted household surveys. Mobile phone surveys offer advantages in terms of cost and ease of implementation. However, their suitability for monitoring perinatal mortality has not been established.

methodsWe use data from the Malawi Rapid Mortality Mobile Phone Survey (RaMMPS) to estimate perinatal mortality rates from two versions of the survey instrument: a full pregnancy history and a shorter truncated pregnancy history. Female respondents of reproductive age were randomly allocated to either of these instruments. The sample was generated through random digit dialling with active strata monitoring. Post-stratification weighting was used to correct for sample selection bias, and estimates are reported with bootstrap confidence intervals. We estimated the stillbirth rate as the synthetic cohort probability of a foetal death with 28+ weeks of gestation over all pregnancies reaching the same gestational age. The perinatal and extended perinatal mortality rates were defined as the probabilities of dying between 28 weeks and 7 or 28 days of life, respectively. RaMMPS estimates are compared to the 2015-2016 Malawi Demographic and Health Survey and estimates published by the United Nations Inter-agency Group for Child Mortality Estimation.

resultsTruncated and full pregnancy histories were administered for 2093 and 2067 women, respectively. Weighted point estimates of the stillbirth (19.81 deaths per 1000 pregnancies, 95%-confidence interval (CI): 14.11-25.62), perinatal (42.41, 95%-CI: 33.91-50.92), and extended perinatal mortality rates (50.11, 95%-CI: 41.56-58.84) from the full pregnancy history instrument are in line with Demographic and Health Survey and United Nations Inter-agency Group for Child Mortality Estimation estimates. In comparison, the mortality estimates from the truncated pregnancy history instrument are higher, but this difference only approaches statistical significance in the case of the stillbirth rate. Post-stratification weighting produces a small upwards adjustment in the estimates.

conclusionMobile phone surveys are a promising method for collecting perinatal mortality data. The full pregnancy history instrument produces more plausible results than the shorter truncated pregnancy history questionnaire where the window of retrospection is restricted.