Stressor Effects on Sex Ratios and Births in the Maltese Population during the First Half of the 20th Century.

BACKGROUND

The sex ratio at birth (male/total = M/F) is expected to approximate 0.515. Stress is known to reduce livebirth M/F. In the first half of the 20th century, Malta was stressed by two World Wars.

OBJECTIVES

This study was carried out in order to analyse changes in reproductive performance and M/F of stillbirths and livebirths in Malta during this period.

METHODS

Livebirth and stillbirth data (1910-1951) were obtained from official published Maltese government reports. Stillbirths were defined as any antenatal loss after 28 weeks of gestation.

RESULTS

This analysis studied 347,562 live and 11,662 stillbirths. For 1919-1951, M/F at birth was 0.517, stillbirth M/F was 0.664, implying 28/40 M/F = 0.522. Assuming conceptional M/F = 0.5, estimated M/F for fetal wastage before 28 weeks was approximately 0.434. There was a decrease in the overall birth rate starting after 1911 to 1921, more marked for 1941-1943 followed by an overshoot in 1943-48. There was a statistically significant drop in M/F livebirths during the periods 1916-21 and 1934-45. Stillbirths decreased significantly after 1935 (M>F). A stillbirth M/F drop in 1937-45 and rise in 1946-51 were statistically significant.

CONCLUSIONS

Birth rate drops in both wars were ascribed to conscription, adverse living conditions and decreased fertility from nutritional restrictions. Both conflicts resulted in short post-war baby booms. The decrease in stillbirths is attributed to increase in antenatal attendances, hospital births and special food rations for pregnant women. The M/F observations suggest that the selective survival of both healthier female and male foetuses is favoured during times of stress.