The effect in the second trimester of pregnancy was most marked.

在怀孕的第4-6个月时影响最为显著。

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These severe leg cramps usually pop up in the second trimester and continue through the third.

这种严重的腿部肌肉抽筋现象通常出现在怀孕中期，并持续整个怀孕后期。

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Almost 90 percent of women experience some form of skin darkening beginning in the second trimester.

几乎90%的女性在怀孕中期都会经历一些形式的皮肤变暗。

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Some states have no time limit, while others allow abortion up to the end of the second trimester, about 27 or 28 weeks into the pregnancy.

CNN: North Dakota governor signs law banning most abortions

To get human retinal cells at the same stage of development, however, would involve taking stem cells from a foetus during the second trimester of pregnancy.

BBC: NEWS | Health | Cell transplants 'restore sight'

It usually ends by the second trimester.

NPR: FDA Approves Return Of Drug For Morning Sickness