Tachysystole affects placental gas exchange by causing what condition?

• A. Stasis in intervillous space preventing maternal and fetal gas exchange
• B. Increased placental perfusion
• C. Decreased uterine contractions
• D. No effect on gas exchange

Answer: (A)

Excessive uterine activity, or tachysystole, reduces placental perfusion because frequent contractions squeeze the arteries feeding the intervillous space. This space is where maternal blood bathes the fetal villi to enable gas exchange. When contractions are too frequent, there’s less time and flow for fresh maternal blood to enter this space, leading to sluggish or stagnant blood in the intervillous space. That stagnation impairs the transfer of oxygen to the fetus and the removal of carbon dioxide, so gas exchange between mother and fetus is hindered. The best description of this effect is stasis in the intervillous space preventing maternal and fetal gas exchange. Increased placental perfusion wouldn’t occur with tachysystole, decreased contractions would improve exchange, and claiming no effect on gas exchange contradicts the physiology of uteroplacental insufficiency.