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Am J Perinatol 2015; 32(14): 1305-1310
DOI: 10.1055/s-0035-1563716
Original Article
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Fetal Gender of the First Born and the Recurrent Risk of Spontaneous Preterm Birth

Esmé I. Kamphuis
1   Center for Reproductive Medicine, Department of Obstetrics and Gynaecology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
3   Department of Obstetrics and Gynecology, VU University Medical Centre, Amsterdam, The Netherlands
,
Bouchra Koullali
1   Center for Reproductive Medicine, Department of Obstetrics and Gynaecology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
,
Michel Hof
2   Department of Clinical Epidemiology, Bioinformatics, and Biostatistics, Academic Medical Centre, Amsterdam, The Netherlands
,
Christianne J. M. de Groot
3   Department of Obstetrics and Gynecology, VU University Medical Centre, Amsterdam, The Netherlands
,
Brenda M. Kazemier
1   Center for Reproductive Medicine, Department of Obstetrics and Gynaecology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
,
Sarah Robertson
4   The Robinson Research Institute | School of Paediatrics and Reproductive Health, University of Adelaide, South Australia, Australia
,
Ben W. J. Mol
4   The Robinson Research Institute | School of Paediatrics and Reproductive Health, University of Adelaide, South Australia, Australia
,
Anita C. Ravelli
1   Center for Reproductive Medicine, Department of Obstetrics and Gynaecology, Academic Medical Centre, University of Amsterdam, Amsterdam, The Netherlands
5   Department of Medical Informatics, Academic Medical Centre, Amsterdam, The Netherlands
› Author Affiliations
Further Information

Publication History

09 July 2015

21 July 2015

Publication Date:
09 September 2015 (online)

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Abstract

Objective To study, in women with a spontaneous preterm birth (sPTB) in the first pregnancy, the effect of fetal sex in that first pregnancy on the recurrent sPTB risk.

Study Design A nationwide retrospective cohort study (data from National Perinatal Registry) on all women with two sequential singleton pregnancies (1999–2009) with the first delivery ending in sPTB <37 weeks. We used logistic regression analysis to study the association between fetal gender in the first pregnancy and the risk of recurrent sPTB. We repeated the analysis for sPTB < 32 weeks.

Results The overall incidence of sPTB <37 weeks in the first pregnancy was 4.5% (15,351/343,853). Among those 15,351 women, the risk of recurrent sPTB <37 weeks was increased when the first fetus was female compared when that fetus was male (15.8 vs. 15.2%; adjusted odds ratio [aOR] 1.2; 95% confidence interval [CI] 1.05–1.3). A similar effect was seen for sPTB <32weeks (8.2 vs. 5.9%; aOR 4.5; 95% CI 1.5–13).

Conclusion Women who suffer sPTB of a female fetus have an increased risk of recurrent sPTB compared with women who suffer sPTB of a male fetus. This information provides proof for the hypothesis that sPTB is due to an independent maternal and fetal factor.

Keywords

fetal gender - recurrent spontaneous preterm birth

Note

This study was presented as poster at the 2015 Annual Meeting, SMFM, San Diego, CA, February 2–7, 2015.