BACKGROUND AND PURPOSE:

• Many women are running during pregnancy, but there is limited research on outcomes
• Kuhrt et al. (BMJ Open Sport & Exercise Medicine, 2018) sought to determine the impact of running during pregnancy on gestational age at delivery and birth weight as indicators of cervical integrity and placental function, respectively

METHODS:

• Retrospective cohort study
• Participants: Women recruited from an international running organization
• Women were categorized into the following groups
  • Those who continued to run during pregnancy
  • Those who did not
• Those who continued were further stratified depending on weekly kilometers and trimester
• Birthweight centiles were adjusting for maternal height, weight, ethnicity and parity, and for neonatal gender and gestational age at delivery
• Small for gestation age: <the 3rd centile
• Large for gestational age: >the 90th centile
• Primary outcomes
  • Gestational age at delivery
  • Birthweight centile
• Secondary outcomes
  • Assisted vaginal delivery rate
  • Prematurity

RESULTS:

• 1,293 women were involved in the study
  • 45% of women did not run in pregnancy
  • 15% stopped in the first trimester
  • 25% stopped in the second trimester
  • 16% ran into their third trimester
• Gestational age at delivery, comparing women who stopped running vs those who continued
  • Not significant: 279.0 vs 279.6 days (P=0.55)
• Birthweight centile, comparing women who stopped running vs those who continued
  • Not significant: 46.9% vs 44.9% (P=0.22)
• Primary outcomes were not affected by mean weekly running distance and trimester
• Assisted vaginal delivery rate was increased in women who ran
  • 27% vs 22% (Odds Ratio 1.32; 95% CI 1.02 to 1.71; P=0.03)
• No difference in preterm birth rate or proportion of babies below 3^rd, 5^th, 10^th or 90^th centile

CONCLUSION:

• Running during pregnancy does not appear to affect gestational age or birthweight centile
• Assisted vaginal delivery rates were high in both groups (approximately 25%)
  • Authors suggest that perhaps increased pelvic floor muscle tone may be explain the increased risk of assisted vaginal delivery
• The authors state “…women who want to continue running during pregnancy can be reassured by their obstetricians that it will not affect the birth weight of their baby significantly or increase the likelihood of a preterm delivery.”

Learn More – Primary Sources:

Is recreational running associated with earlier delivery and lower birth weight in women who continue to run during pregnancy? An international retrospective cohort study of running habits of 1293 female runners during pregnancy.

Related ObG Topics:

Does Exercise in Pregnancy Decrease Risk of Gestational Diabetes?

Does Exercise During Pregnancy Impact Hypertension or Macrosomia?

Is Maternal Core Temperature Elevated Beyond a Critical Threshold During Exercise in Pregnancy?