Maternal Physical Activity at Term and Spontaneous Labor: A Case-Crossover Study.

Area of Science:

• Obstetrics and Gynecology
• Maternal-Fetal Medicine
• Reproductive Health

Background:

• Understanding factors influencing spontaneous labor (SL) onset is crucial for optimizing birth timing and outcomes.
• Antenatal physical activity is a modifiable behavior with potential implications for labor initiation.

Purpose of the Study:

• To investigate the association between different types of antenatal physical activity and the risk of spontaneous labor onset.
• To explore whether recreational, occupational, or any physical activity influences the timing of spontaneous labor.

Main Methods:

• A case-crossover design was employed using data from 541 participants in the "third pregnancy, infection, and nutrition" study.
• Physical activity (recreational, occupational, any) was assessed via questionnaire in the week and 24 hours prior to spontaneous labor onset.
• The study examined the risk of SL onset within 24 hours following reported physical activity.

Main Results:

• Overall, 21% reported any physical activity in the week prior to SL, with 5% reporting it in the 24 hours before.
• Any or occupational physical activity in the 24 hours before SL was associated with a decreased likelihood of labor onset.
• At least 30 minutes of recreational physical activity in the 24 hours before SL was associated with an increased likelihood of labor onset.

Conclusions:

• Recreational physical activity near term may increase the likelihood of spontaneous labor onset.
• Occupational physical activity does not appear to increase the likelihood of spontaneous labor onset.
• The possibility of reverse causality, where labor onset influences physical activity, cannot be excluded.