Final answer:
During the second trimester of pregnancy, maternal cardiac output actually increases to support the growing fetus, making the statement false. Cell numbers in the fetus increase as they double with every division during cleavage. The correct option is b).
Step-by-step explanation:
The statement that maternal cardiac output is decreased by 20-30% during the second trimester is false. In fact, during the second trimester, there is an increase in cardiac output to support the growing fetus.
The placenta, which has taken over many functions for the baby, requires more blood flow to facilitate the exchange of oxygen and nutrients. Moreover, the number of cells during cleavage actually doubles with every cell division, ensuring the exponential growth of the fetus early in development.
Additional information related to fetal development and maternal changes during pregnancy indicates that in a healthy young adult, cardiac output actually decreases when the heart rate increases above 160 bpm due to the decline in stroke volume.
Furthermore, it is factual that one umbilical vein carries oxygen-rich blood from the placenta to the fetal heart and that the fetus can produce urine. However, the statement that the umbilical artery carries oxygenated blood to the fetus is false; it rather carries deoxygenated blood away from the fetus. Option b) is the correct one.