Waiting time to pregnancy and pregnancy outcome among Danish workers in the textile, clothing, and footwear industries

Abstract

The relationship between time from planned to achieved pregnancy and pregnancy outcome has been studied in a group of 18,658 workers in the textile, clothing and footwear industries. Information on pregnancy outcome and delay in conception in the period 1979-84 was collected by self administered questionnaires in 1985. The response rate was 70.3%. During the study period there had been 5,171 live births and 708 spontaneous abortions. Information on delay in conception was collected in broad categories. The data were analysed by means of a newly developed statistical parametric model in order to collect all possible information from the highly grouped data. Median waiting time before a pregnancy which ended in spontaneous abortion was 1.68 times longer than median waiting time before a pregnancy leading to a live birth. There seems to be a correlation between the length of the waiting time and abortion.

PIP: This study examined, in a cohort of 18,658 women members 40 years of age in the textile, clothing, and footwear national union in 1985 in Denmark, the time span between planned and achieved pregnancy as it relates to pregnancy outcome. The response rate of the self-administered questionnaire was 70.3%. Information on all pregnancies between 1979 and 1984 was collected. Outcome data revealed 5171 pregnancies and 708 spontaneous abortions. Distribution of waiting times was modeled using Boldsen and Schaumburg techniques and assumes constant conception probability. Differences were represented by a gamma distribution with defined alpha and beta parameters. the results show that the waiting times resulting in spontaneous abortion are more likely to be unknown (chi square = 5.49, df = 1, p.05). There is a high likelihood that unplanned pregnancies result in spontaneous abortion (odds ration = 2.72, 95% confidence interval = 1.93-3.77). Abortion risk expected values closely approximate observed values of pregnancy resulting in spontaneous abortion. The median waiting time span for a pregnancy leading to spontaneous abortion is 1.68 times the median waiting time for pregnancy with a live birth. The risk of spontaneous abortion increases with the length of waiting time. Social conditions such as heavy smoking regimes, exposure to industrial chemicals, and lower educational levels may partially explain the results. There was a longer waiting time before conception also. A similar study among pharmacy assistants showed that outcome of pregnancy was unrelated to waiting time. Pregnancies may be considered unplanned more often when spontaneous abortion results, and may bias results. The long waiting times may mean impaired conception or very early pregnancy loss or an unknown biological explanation. Further research is suggested on other groups of women and waiting times.