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Exercise during pregnancy and risk of Cesarean delivery in nulliparous women: A large population-based cohort study

American Journal of Obstetrics and Gynecology, In Press, Accepted Manuscript, Available online 23 August 2016, Available online 23 August 2016

Abstract

Background

Vaginal delivery for the first birth is of great importance for further obstetric performance for the individual woman. Given the rising cesarean delivery (CD) rates worldwide over the past decades, the search for modifiable factors associated with CD is needed. Exercise may be a modifiable factor associated with type of delivery, but the results of previous studies are not conclusive.

Objective

To investigate the association between exercise during pregnancy and CD, both acute and elective, in nulliparous women.

Study design

A population-based cohort study involving 39,187 nulliparous women with a singleton pregnancy enrolled in the Norwegian Mother and Child Cohort Study (MoBa) between 2000 and 2009. All women answered two questionnaires in pregnancy weeks 17 and 30. Acute and elective CD were obtained from the Medical Birth Registry of Norway. Information on exercise frequency and type was assessed prospectively by questionnaires in pregnancy weeks 17 and 30. Generalized linear models estimated risk differences (RD) of acute and elective CD for different frequencies and types of exercise during pregnancy weeks 17 and 30. We used restricted cubic splines to examine dose-response associations of exercise frequency and acute CD. A test for non-linearity was also conducted.

Results

The total CD rate was 15.4% (n=6030), of which 77.8% (n=4689) was acute CD. Exercise during pregnancy was associated with a reduced risk of CD, particularly for acute CD. A nonlinear association was observed for exercise frequency in weeks 17 and 30 and risk of acute CD (test for nonlinearity, P =0.003 and P =0.027, respectively). The largest risk reduction was observed for acute CD among women exercising more than five times weekly during weeks 17 (-2.2 percent) and 30 (-3.6 percent) compared to non-exercisers (test for trend P<.001). Reporting high impact exercises in weeks 17 and 30 was associated with the greatest reduction in risk of acute CD (-3.0 and -3.4 percent, respectively).

Conclusion

Compared to non-exercisers, regular exercise and high impact exercises during pregnancy are associated with reduced risk of having an acute CD in first-time mothers.

Regular exercise during pregnancy is associated with a reduced risk of acute cesarean delivery in first-time mothers.

Key words: pregnancy, mode of delivery, parity, physical activity, MoBa, prospective study, risk difference.

Footnotes

1 Norwegian National Advisory Unit on Women’s Health, Department of Obstetrics and Gynaecology, Oslo University Hospital, Rikshospitalet, Oslo, Norway

2 Domain of Mental and Physical Health, Norwegian Institute of Public Health, Oslo, Norway

3 Department of Sports Medicine, Norwegian School of Sport Sciences, Oslo, Norway

Corresponding author: Katrine M. Owe, Mental and Physical Health, Norwegian Institute of Public Health, PO BOX 4404 Nydalen, 0403 OSLO, NORWAY. Phone: +47 916 83 023.

Conflict of interest: None of the authors report any conflict of interest.

Funding: The Norwegian Mother and Child Cohort Study is supported by the Norwegian Ministry of Health and the Ministry of Education and Research, NIH/NIEHS (contract no N01-ES-75558), NIH/NINDS (grant no.1 UO1 NS 047537-01 and grant no. 2 UO1 NS 047537-06A1). None of the funding sources have taken part in the design and conduct of the study; collection, analysis, or interpretation of the data; and preparation, review, or approval of manuscript.

Ethical approval: The study was approved by the Regional Committee for Medical Research Ethics (S-95113) and The Norwegian Data Protection Authority.