Maternal factors and the male to female birth ratio in Malta

Abstract

Introduction: The sex ratio at birth is commonly calculated as the total male live births divided by all live births, and is represented as M/F. A multitude of factors influence M/F, especially stress, which increases male foetal losses during pregnancy. This study was carried out in order to ascertain whether any maternal or perinatal relevant factors influenced M/F in Malta. Methods: National Obstetric Information System data was used for the period 2012-2015. Non-Maltese mothers were excluded. Factors analysed were maternal age, marital status, education, body mass index, regularity of menses, utilisation of assisted reproductive technology, previous diabetes mellitus, previous miscarriages, abortions, ectopic pregnancies, vaginal deliveries, caesarean sections, livebirths, early and late neonatal deaths, stillbirths and premature deliveries. Intra-partum conditions included infection, cardiovascular disorders and all forms of diabetes mellitus. Results: This study analysed 14498 births. None of the above mentioned variables was significantly linked to the M/F ratio. Discussion: Our dataset failed to find any variables that influenced M/F, including stressing variables. However our study may have been underpowered due to the small numbers of births and the relative rarity of the various conditions. Alternatively, in Malta, such variables may produce little or no stress due to hitherto unknown mitigating factor/s.