在懷孕期間的四周，胚胎並不比一顆飯粒大；但當其成為胎兒後，將會急速成長

在懷孕期間的四周，胚胎並不比一顆飯粒大；但當其成為胎兒後，將會急速成長，約在20周時，胎兒大概會有25公分長。

結果 (英文) 1:

In the four weeks during pregnancy, the embryo no bigger than a rice; but when it became the fetus will grow rapidly, at about 20 weeks, the fetus is likely to be 25 cm long.

結果 (英文) 2:

During the four weeks of pregnancy, the embryo is no larger than a meal grain, but when it becomes a fetus, it will grow rapidly, about 25 centimeters long at about 20 weeks.

結果 (英文) 3:

During the four weeks of pregnancy, the embryo is not larger than a rice grain; however, when it becomes a fetus, it will grow rapidly. At about 20 weeks, the fetus will be about 25 cm long.