The impact of fetal gender and ethnicity on the risk of spontaneous preterm delivery in women with symptoms of preterm labor

Femke F. Wilms*, Jolande Y. Vis, Martijn A. Oudijk, Anneke Kwee, Martina M. Porath, Hubertina C.J. Scheepers, Marc E. A. Spaanderman, Kitty W. M. Bloemenkamp, Antoinette C. Bolte, Caroline J. Bax, Jerome M. J. Cornette, Johannes J. Duvekot, Bas W. A. Nij Bijvanck, Jim van Eijck, Maureen T. M. Franssen, Krystyna M. Sollie, Frank P. H. A. Vandenbussche, Mallory D. Woiski, Joris A. M. van der Post, Patrick M. M. BossuytBrent C. Opmeer, Ben W. J. Mol, Gert-Jan van Baaren

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


Objective: The objective of this study is to evaluate the relation among fetal gender, ethnicity, and preterm labor (PTL) and preterm delivery (PTD).Methods: A secondary analysis was performed of a prospective cohort study including women with symptoms of PTL between 24 and 34 weeks. The proportion of women carrying a male or female fetus at the onset of PTL was calculated. Gestational age at delivery and risk of PTD of both fetal genders was compared and interaction of fetal gender and maternal ethnicity on the risk of PTD was evaluated.Results: Of the 594 included women, 327 (55%) carried a male fetus. Median gestational age at delivery in women pregnant with a male fetus was 37 5/7 (IQR 34 4/7-39 1/7) weeks compared with 38 1/7 (IQR 36 0/7-39 5/7) weeks in women pregnant with a female fetus (p=0.032). The risk of PTD did not differ significantly. In Caucasians, we did find an increased risk of PTD before 37 weeks in women pregnant with a male fetus (OR 1.9 (95% CI 1.2-3.0)).Conclusions: The majority of women with PTL are pregnant with a male fetus and these women deliver slightly earlier. Race seems to affect this disparity.
Original languageEnglish
Pages (from-to)3563-3569
JournalJournal of Maternal-Fetal & Neonatal Medicine
Issue number21
Publication statusPublished - Nov 2016


  • Ethnicity
  • fetal gender
  • preterm delivery
  • preterm labor

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