Birth characteristics in a clinical sample of women seeking infertility treatment: a case–control study

OBJECTIVE: To determine the distribution of low birth weight (LBW), preterm birth, small for gestational age (SGA) and large for gestational age (LGA) by main cause of infertility (female, combined, male, unexplained) in women seeking infertility treatment. DESIGN: A case–control study. SETTING: A Centre for Reproductive Medicine in Sweden. PARTICIPANTS: All women (n=1293) born in Sweden in 1973 or later and who were part of heterosexual couples seeking infertility treatment at a Centre of Reproductive Medicine from 2005 to 2010 were asked to participate. Those who had not begun the diagnostic process and who declined participation in the study were excluded. In total, 1206 women (94.5%) participated in the study. MAIN OUTCOME MEASURES: Main cause of infertility (female, combined, male, unexplained) collected from the patients’ medical charts. LBW (<2500 g), preterm birth (<37 weeks), SGA (<−2SD of the mean weight for the gestational length) and LGA (>+2SD of the mean weight for the gestational length), collected from the Swedish Medical Birth Register. RESULTS: The risk of being born with LBW was increased about 2.4 times (OR=2.40, CI 1.13 to 5.07, p=0.02) in women seeking treatment for infertility due to female causes rather than for male or unexplained causes. Women with a female infertility factor were 2.7 times more likely to be born SGA (OR=2.73, CI 1.02 to 7.34, p=0.047) compared with those in whom the cause of infertility was unexplained. CONCLUSIONS: Women born with LBW or SGA seem to suffer an increased risk of infertility due to a female factor. Thus, infants born with birth characteristics that deviate from the norm may be at greater risk of difficulties in childbearing later on in life. Since this study is the first of its kind, more studies are needed to verify the associations found in this study and to determine their nature.