The impact of body position on vital capacity among pregnant women in the second trimester.

Background: Pregnancy introduces significant physiological changes, notably impacting respiratory dynamics, especially during the second trimester. Data remain inconclusive about how body posture might influence lung function in pregnant women. We aimed to examine the impact of body position on slow vital capacity in pregnant women during their second trimester.

Methods: This observational study was carried out at King Khalid Hospital in Saudi Arabia, involving pregnant women in their second trimester, from 14 to 26 weeks of gestation. We utilized the KoKo® Legend Portable Office Spirometer to measure slow vital capacity (SVC) in both sitting and standing positions. Participants' demographic details were recorded, ensuring a comprehensive analysis that accounted for age, BMI, and gestational age.

Results: 136 pregnant women participated in this study, a paired-sample -test revealed no statistically significant difference between sitting (M = 2.31, SD = 0.49) and standing (M = 2.33, SD = 0.5) positions,  = 0.24, However; the mean value of SVC in sitting position was significantly different between 4th month of pregnancy (M = 2.17, SD = 0.44) and 6th month of pregnancy (M = 2.45, SD = 0.48),  = 0.016.

Conclusion: The performance of the SVC in both positions was not significantly affected. However, an increase in gestational age had a notable impact on SVC performance, particularly during sitting positions, due to the changes in respiratory physiology during pregnancy.