title: The impact of fetal gender and ethnicity on the risk of spontaneous preterm delivery in women with symptoms of preterm labor.
abstract: 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.
authors.affiliation: a Department of Obstetrics & Gynecology , Máxima Medical Center , Veldhoven , Netherlands .
authors.forename: Femke F
authors.initials: FF
authors.lastname: Wilms
authors.affiliation: b Department of Clinical Chemistry & Haematology , University Medical Center Utrecht , Utrecht , the Netherlands .
authors.forename: Jolande Y
authors.initials: JY
authors.lastname: Vis
authors.affiliation: c Department of Obstetrics & Gynecology , University Medical Center Utrecht , Utrecht , Netherlands .
authors.forename: Martijn A
authors.initials: MA
authors.lastname: Oudijk
authors.affiliation: c Department of Obstetrics & Gynecology , University Medical Center Utrecht , Utrecht , Netherlands .
authors.forename: Anneke
authors.initials: A
authors.lastname: Kwee
authors.affiliation: a Department of Obstetrics & Gynecology , Máxima Medical Center , Veldhoven , Netherlands .
authors.forename: Martina M
authors.initials: MM
authors.lastname: Porath
authors.affiliation: d Department of Obstetrics & Gynecology , Maastricht University Medical Center , Maastricht , Netherlands .
authors.forename: Hubertina C J
authors.initials: HC
authors.lastname: Scheepers
authors.affiliation: d Department of Obstetrics & Gynecology , Maastricht University Medical Center , Maastricht , Netherlands .
authors.forename: Marc E A
authors.initials: ME
authors.lastname: Spaanderman
authors.affiliation: e Department of Obstetrics & Gynecology , Leiden University Medical Center , Leiden , Netherlands .
authors.forename: Kitty W M
authors.initials: KW
authors.lastname: Bloemenkamp
authors.affiliation: f Department of Obstetrics & Gynecology , VU University Medical Center , Amsterdam , Netherlands .
authors.forename: Antoinette C
authors.initials: AC
authors.lastname: Bolte
authors.affiliation: f Department of Obstetrics & Gynecology , VU University Medical Center , Amsterdam , Netherlands .
authors.forename: Caroline J
authors.initials: CJ
authors.lastname: Bax
authors.affiliation: g Department of Obstetrics & Gynecology , Erasmus University Medical Center , Rotterdam , Netherlands .
authors.forename: Jérôme M J
authors.initials: JM
authors.lastname: Cornette
authors.affiliation: g Department of Obstetrics & Gynecology , Erasmus University Medical Center , Rotterdam , Netherlands .
authors.forename: Johannes J
authors.initials: JJ
authors.lastname: Duvekot
authors.affiliation: h Department of Obstetrics & Gynecology , Isala Clinics , Zwolle , Netherlands .
authors.forename: Bas W A
authors.initials: BW
authors.lastname: Nij Bijvanck
authors.affiliation: h Department of Obstetrics & Gynecology , Isala Clinics , Zwolle , Netherlands .
authors.forename: Jim van
authors.initials: Jv
authors.lastname: Eijck
authors.affiliation: i Department of Obstetrics & Gynecology , University Medical Center Groningen , Groningen , Netherlands .
authors.forename: Maureen T M
authors.initials: MT
authors.lastname: Franssen
authors.affiliation: i Department of Obstetrics & Gynecology , University Medical Center Groningen , Groningen , Netherlands .
authors.forename: Krystyna M
authors.initials: KM
authors.lastname: Sollie
authors.affiliation: j Department of Obstetrics & Gynecology , Radboud University Hospital Nijmegen , Nijmegen , Netherlands .
authors.forename: Frank P H A
authors.initials: FP
authors.lastname: Vandenbussche
authors.affiliation: j Department of Obstetrics & Gynecology , Radboud University Hospital Nijmegen , Nijmegen , Netherlands .
authors.forename: Mallory D
authors.initials: MD
authors.lastname: Woiski
authors.affiliation: k Department of Obstetrics & Gynecology , Academic Medical Center , Amsterdam , Netherlands .
authors.forename: Joris A M
authors.initials: JA
authors.lastname: van der Post
authors.affiliation: l Clinical Research Unit, Academic Medical Center , Amsterdam , Netherlands , and.
authors.forename: Patrick M M
authors.initials: PM
authors.lastname: Bossuyt
authors.affiliation: l Clinical Research Unit, Academic Medical Center , Amsterdam , Netherlands , and.
authors.forename: Brent C
authors.initials: BC
authors.lastname: Opmeer
authors.affiliation: m The Robinson Institute, School of Paediatrics and Reproductive Health, University of Adelaide , Adelaide , Australia.
authors.forename: Ben W J
authors.initials: BW
authors.lastname: Mol
authors.affiliation: k Department of Obstetrics & Gynecology , Academic Medical Center , Amsterdam , Netherlands .
authors.forename: Gert-Jan
authors.initials: GJ
authors.lastname: van Baaren
mesh_terms: D000328:Adult; D054791:Cervical Length Measurement / Q000706:statistics & numerical data; D016009:Chi-Square Distribution; D005260:Female; D047109:Fetal Development; D005353:Fibronectins / Q000032:analysis; D005865:Gestational Age; D006801:Humans; D008297:Male; D007752:Obstetric Labor, Premature / Q000208:ethnology*; D011247:Pregnancy; D047928:Premature Birth / Q000208:ethnology*; D011446:Prospective Studies; D012306:Risk; D017678:Sex Distribution; D012737:Sex Factors; D044465:White People / Q000208:ethnology
chemical_list: C403421:FFN protein, human; D005353:Fibronectins
keywords: Ethnicity; fetal gender; preterm delivery; preterm labor