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Prenatal tobacco exposure and other life-style related risk factors for low semen quality and subfecundity. Epidemiologic studies in Denmark


Cecilia Høst Ramlau-Hansen  


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Accepted by: Faculty of Health Sciences University of Aarhus
Defended on: December 4, 2007
Official opponents: Sjurdur F. Olsen , Anne-Marie Nybo Andersen , Aleksander Giwercman
Tutors: Ane Marie Thulstrup , Lone Storgaard , Jens Peter Bonde

Published in the PhD Database: December 10, 2007


English abstract
This PhD dissertation was carried out at Department of Occupational Medicine, Aarhus University Hospital, and accepted for defense by the Faculty of Health Sciences, University of Aarhus. The dissertation comprises seven original articles and a summary report.

The semen quality has possibly decreased the past 60-70 years, and up to 25% of all Danish men have a sperm concentration so low that their fecundity is affected. An increasing number of couples seek infertility treatment, and subfecundity and infertility constitutes a major public health concern.

The aim of this dissertation was to investigate the association between prenatal exposures (e.g. tobacco) and semen quality. Additionally, we wanted to assess the association between current male smoking and semen quality as well as the association between parental overweight and waiting time to pregnancy. Finally, we wanted to validate the method used to obtain measurements of testicular volumes.

To examine the association between the prenatal exposures and semen quality, we conducted a prospective follow-up study, including 347 young men. These were sons of mothers who participated in the ¿Healthy Habits for Two¿ study during pregnancy and provided information on lifestyle and factors related to health before and during pregnancy. We found an inverse dose-response relationship between maternal smoking during pregnancy and semen quality in the sons. Sons of mothers examined or treated for childlessness had poorer semen quality than sons of mothers not examined or treated for childlessness, and we found indication of decreased semen quality among sons of overweight mothers.

The association between current male smoking and semen quality was investigated by pooled analysis on data from seven former conducted semen quality studies. A total of 2,562 men were included, and we observed an inverse association between smoking and semen quality.

In the Danish National Birth, we explored the association between overweight and fecundity among 47,835 couples in addition to changes in weight and fecundity over time. We observed a dose-response relation between BMI and subfecundity after exclusion of underweight men and women, and for women was a weight gain between two pregnancies associated with prolonged waiting time to pregnancy.

To validate self-measurements of testicular volumes with an orchodimeter, we compared self-measurements with measurements obtained by an experienced examiner among 58 sperm donors and sperm donor candidates. We found that sperm donors and sperm donor candidates obtained valid measurements of their own testicular volumes.



Danish abstract
Denne ph.d.-afhandling udgår fra Arbejdsmedicinsk klinik, Århus Universitetshospital, Århus Sygehus. Den omfatter 7 originalartikler publiceret 2006-7 og en sammenfattende redegørelse.

Formålet var at undersøge sammenhængen mellem 1) prænatale eksponeringer og sædkvalitet, 2) aktuel rygning og sædkvalitet samt 3) forældres overvægt og ventetid til graviditet. Endelig ønskedes målemetoden til bedømmelse af testikelstørrelse valideret.

Sammenhængen mellem prænatale eksponeringer og sædkvalitet undersøgtes i et follow-up studie, hvori 347 unge mænd deltog. Disse var sønner af mødre, der under graviditeten havde besvaret spørgeskema vedrørende bl.a. livsstil før og under graviditet. Der observeredes en omvendt dosis-respons sammenhæng mellem mødres rygning under graviditeten og sønners sædkvalitet. Sønner af mødre, der var undersøgt eller behandlet for barnløshed, havde dårligere sædkvalitet end sønner af mødre, der ikke var undersøgt eller behandlet, og der var tegn på, at højt maternelt BMI måske påvirker sønners sædkvalitet negativt.

Associationen mellem aktuel rygning og sædkvalitet belystes ved at kombinere data fra 7 tidligere sædkvalitetsstudier. En omvendt sammenhæng blev observeret.

I kohorten Bedre Sundhed for Mor og Barn blev associationen mellem 47.835 pars overvægt og fekunditet samt sammenhængen mellem ændringer i vægt og fekunditet over tid undersøgt. En dosis-respons sammenhæng mellem BMI og subfekunditet blev fundet, og for kvinder var vægtstigning mellem to graviditeter associeret med forøget ventetid til graviditet.

Endelig vistes det, at sæddonorer og -kandidater opnåede valide selvmålinger af testikelstørrelse i forhold til målinger foretaget af en rutineret undersøger.