A PROSPECTIVE COHORT STUDY OF THE ASSOCIATION BETWEEN VIGOROUS - - PowerPoint PPT Presentation

Sarah Lee

Research Midwife Central Manchester University Hospitals NHS Foundation Trust

Master of Clinical Research School of Nursing, Midwifery and Social Work The University of Manchester

A PROSPECTIVE COHORT STUDY OF THE ASSOCIATION BETWEEN VIGOROUS EXERCISE DURING PREGNANCY AND PREGNANCY OUTCOME

NHS guidelines recommend that adults should undertake 150 minutes of moderate intensity aerobic activity every week (NHS, 2013) The Royal College of Obstetricians and Gynaecologists recommend that pregnant women should participate in four aerobic exercise sessions per week lasting at least 30 minutes each (RCOG, 2006) A Cochrane review from 2010 reported the impact of prolonged and repeated aerobic exercise on clinical outcomes for mother and infant are still unknown (Kramer and McDonald, 2010)

Introduction

The broad aim of the literature search was to examine the evidence for undertaking recreational exercise whilst pregnant The PICO framework was used to frame and answer the clinical question (Schardt et al., 2007)

Patient = pregnant women Intervention = recreational exercise in pregnancy Comparison = no exercise in pregnancy Outcome = all relevant clinical outcomes of pregnancy

“Do pregnant women who carry out recreational exercise in pregnancy have different clinical outcomes than those who do not carry out recreational exercise?”

Literature Review

An online search was undertaken in September 2011 and repeated in September 2013 Seventeen papers reporting primary research studies and two systematic reviews formed the basis of the literature review Four themes emerged concerning exercise in pregnancy and pregnancy outcome

• 1. Effect of exercise on mode of birth
• 2. Effect of exercise on birth weight
• 3. Effect of exercise on gestation at birth
• 4. Effect of exercise on length of labour

Literature Review

Findings were mixed with all studies having faults in their design One small study showed that exercise increases the chance of a spontaneous vaginal birth when compared with instrumental birth One study found women who exercise have a non-significant increased chance of a vaginal birth (unassisted or assisted) Two studies established that exercise does not affect mode of birth

Exercise and mode of birth

There is conflicting evidence regarding exercise in pregnancy and birth weight The latest Cochrane review (Kramer and McDonald, 2010) shows that exercise has no impact on birth weight Other studies demonstrate that women who exercise: – are less likely to have an LGA infant – are protected against LBW infants

Exercise and birth weight

Exercise may influence all of these outcomes Data are inconsistent and conflicting The main gaps in current knowledge are how exercise in pregnancy affects – mode of birth – birth weight.

Summary of findings

The study aimed to investigate the relationship between vigorous exercise during the first 21 weeks of pregnancy and its effect on – mode of birth – birth weight – onset of labour – length of labour The hypothesis was that women undertaking vigorous exercise in the first 21 weeks of pregnancy had an increased chance of a spontaneous vaginal birth at term

Research Question

Data for this study were collected as part of the SCOPE study from 2004 to 2012

– A prospective, international multicentre cohort study of healthy nulliparous women with a singleton pregnancy – Participants completed a lifestyle questionnaire at two time points in their pregnancy to provide data on vigorous exercise

Secondary analysis of data from SCOPE to examine the influence

• f exercise on pregnancy outcome

3376 women with uncomplicated pregnancies were extracted from the SCOPE dataset for this study A quantitative approach to analysis was used

Methods

Vigorous exercise question in the SCOPE lifestyle questionnaire

How often have you engaged in vigorous exercise in the last month? (exercise which made you breathe harder or puff or pant such as tennis, jogging, aerobics, heavy gardening, rollerblading, skiing, rowing, rowing/cycling machine) 1 - Never 2 - Once a week 3 - 2-3 time each week 4 - 4-6 times per week 5 - Daily 6 - More than once a day

The Lifestyle Questionnaire

Closed questions answered by participants in the lifestyle questionnaires were converted into numerical answers for statistical analysis using IBM SPSS 20 Main analysis involved the estimation of associations between vigorous exercise and clinical outcomes of pregnancy, adjusted for the presence of other potentially confounding factors A statistical significance level of p ≤ 0.05 was used for all tests performed

Analysis

• Pregnancy weeks 11-15

– 2175 (64.4%) never exercised – 1105 (32.7%) exercised 1-3 times per week – 96 (2.8%) exercised 4+ times per week

• Pregnancy weeks 16-20

– 2012 (61.9%) never exercised – 812 (25.0%) exercised 1-3 times per week – 426 (13.1%) exercised 4+ times per week

Prevalence of Exercise in Pregnancy

Engaged in vigorous exercise between 11-15 weeks

Whole cohort Statistical Analysis Never 1-3 times per week ≥ 4 times per week Sample size (N) 2175 (64.4%) 1105 (32.7%) 96 (2.8%) 3376

Mode of birth Spontaneous vaginal birth 973 (44.8%) 543 (49.1%) 51 (53.1%)

1567 (46.4%) X

2 = 11.67

df = 6

p=0.070

Operative vaginal Birth 641 (29.5%) 275 (24.9%) 27 (28.1%) 943 (27.9%) Pre-labour Caesarean 152 (7.0%) 83 (7.5%) 5 (5.2%) 240 (7.1%) Caesarean in Labour 408 (18.8%) 204 (18.5%) 13 (13.5%) 625 (18.5%)

Mode of Birth

Engaged in vigorous exercise between 16-20 weeks

Whole Cohort Statistical Analysis Never 1-3 times per week ≥ 4 times per week Sample Size (N) 2012 (61.9%) 812 (25.0%) 426 (13.1%) 3250

Mode of birth Spontaneous vaginal birth 891 (44.3%) 418 (51.5%) 201 (47.2%)

1510 (46.5%) X

2 = 14.64

df=6

p=0.023

Operative Vaginal 594 (29.5%) 202 (24.9%) 112 (26.3%) 908 (27.9%) Pre-labour Caesarean 137 (6.8%) 59 (7.3%) 29 (6.8%) 225 (6.9%) Caesarean in labour 389 (19.3%) 133 (16.4%) 84 (19.7%) 606 (18.7%)

Mode of Birth

A Significant Result!

Mode of Birth

Statistical Analysis

SVD

Operative vaginal birth Prelabour LSCS LSCS in labour Whole Cohort Sample size (N) 1567 943 240 625 3375

Engaged in vigorous exercise at 15 weeks Never 973 (44.8%)

641 (29.5%) 152 (7.0%) 408 (18.8%) 2174 (100%) Pearson X

2=9.22

df = 3

p=0.026

≥ 1 per week 594 (49.5%)

302 (25.1%) 88 (7.3%) 217 (18.1%) 1201 (100%)

Engaged in vigorous exercise at 20 weeks Never 891 (44.3%)

594 (29.5%) 137 (6.8%) 389 (19.3%) 2011 (100%) Pearson X

2=11.57

df = 3

p=0.009

≥ 1 per week 619 (50.0%)

314 (25.4%) 88 (7.1%) 217 (17.5%) 1238 (100%)

very similar results and both statistically significant

Mode of Birth

Bivariable analyses demonstrated that women who performed vigorous exercise in weeks 11-15 or 16-20 of pregnancy were more likely to have a spontaneous vaginal birth compared with an operative vaginal birth or caesarean section in labour Multivariable analyses confirmed that any vigorous exercise in weeks 11-20 was associated with spontaneous vaginal birth

Study findings: Mode of Birth

Engaged in vigorous exercise between 11-15 weeks Whole cohort Statistical Analysis Never 1-3 times per week ≥ 4 times per week Sample Size (N) 2175 (64.4%) 1105 (32.7%) 96 (2.8%) 3376 Birth weight (grams) Mean birth weight (SD) 3581g (400.19) 3624g (392.75) 3524g (409.98) 3593.46 (398.60) F = 5.670 df = 2 and 3373

p=0.003

95% confidence Interval 3564.35 to 3598.01 3600.48 to 3646.84 3441.01 to 3607.24 3580.01 to 3606.91 Range 2546 to 5110 2600 to 4940 2645 to 4990 2646 to 5110

Birth weight

A Significant Result!

Engaged in vigorous exercise between 16-20 weeks Whole Cohort Statistical Analysis Never 1-3 times per week ≥ 4 times per week Sample Size (N) 2012 (61.9%) 812 (25.0%) 426 (13.1%) 3250 Birth weight (grams) Mean birth weight (SD) 3586g (401.39) 3607g (405.02) 3580g (361.26) 3590.56 (397.29) F = 0.985, df = 2 and 1083.302

p=0.374

95% confidence interval 3568.46 to 3603.56 3579.31 to 3635.11 3545.90 to 3614.70 3576.89 to 3601.22 Range 2546 to 5060 2600 to 5110 2605 to 4635 2546 to 5110

Birth weight

Difference in birth weight p-value

95% confidence interval for birth weight Lower bound Upper bound

Vigorous exercise at 15 weeks 33g p=0.021

5.036 60.852

Vigorous exercise at 20 weeks 13g p=0.352

• 14.639

41.108 BMI at 15 weeks 17g <0.001 13.72 19.906 Age of participant

• 1.7g

0.252

• 4.783

1.253 Smoking status at 15 weeks

• 118g

<0.001

• 165.649
• 69.589

Birth weight

Bivariable analyses demonstrated that in pregnancy weeks 11-15 exercise was associated with a slight increase in birth weight – Women who vigorously exercised 1-3 times per week during weeks 11-15 were more likely to give birth to heavier infants than those who did not exercise at all – Women who vigorously exercised four or more times per week had the lightest infants – Difference in mean birth weight was only 100g Multivariable analyses confirmed any vigorous exercise in weeks 11-15 was associated with an increase in birth weight

Study findings: Birth weight

The results of this study suggest that vigorous exercise in low risk nulliparous women – slightly, but significantly, increases the chance of a normal vaginal birth – slightly, but significantly, increases birth weight The result of this study supports the current guidance advocating that women continue to exercise in pregnancy

Conclusion

Supervisors Dr Tracey Mills and Dr Malcolm Campbell The women who participated in the SCOPE study, the research midwives and the SCOPE consortium for allowing me access to this data

Any Questions?

Acknowledgements