Does postponement of first pregnancy increase gender differences in sickness absence? A register based analysis of Norwegian employees in 1993-2007.

Background: From 1970-2012, the average age at first delivery increased from 23.2-28.5 in Norway. Postponement of first pregnancy increases risks of medical complications both during and after pregnancy. Sickness absence during pregnancy has over the last two decades increased considerably more than in non-pregnant women. The aim of this paper is twofold: Firstly to investigate if postponement of pregnancy is related to increased sickness absence and thus contributing to the increased gender difference in sickness absence; and secondly, to estimate how much of the increased gender difference in sickness absence that can be accounted for by increased sickness absence amongst pregnant women.

Methods: We employed registry-data to analyse sickness absence among all Norwegian employees with income equivalent to full-time work in the period 1993-2007.

Results: After control for age, education, and income, pregnant women's sickness absence (age 20-44) increased on average 0.94 percentage points each year, compared to 0.29 in non-pregnant women and 0.14 in men. In pregnant women aged 20-24, sickness absence during pregnancy increased by 0.96 percent points per calendar year, compared to 0.60 in age-group 30-34. Sickness absence during pregnancy accounted for 25% of the increased gender gap in sickness absence, accounting for changes in education, income and age.

Conclusions: Postponement of first pregnancy does not explain the increase in pregnant women's sickness absence during the period 1993-2007 as both the highest level and increase in sickness absence is seen in the younger women. Reasons are poorly understood, but still important as it accounts for 25% of the increased gender gap in sickness absence.