1.   In pigs, for example, retrieving healthy eggs and maintaining pregnancy was difficult, Ayares said.

2.   Mifepristone works by counteracting progesterone, a hormone that is needed to maintain a pregnancy.

3.   Progesterone is essential to maintaining pregnancy, and blocking it leads to a sloughing within the uterus and bleeding that detaches the fetus.

4.   Progesterone is essential to maintaining pregnancy, and blocking it leads to a sloughing of the uterus and bleeding that detaches the fetus.

5.   The pills block progesterone, a hormone essential for maintaining pregnancy.

6.   Mifepristone blocks action of a hormone essential for maintaining pregnancy.

7.   The pill blocks action of a hormone essential for maintaining pregnancy.

8.   Women swallow mifepristone, which blocks a hormone essential for maintaining pregnancy.

v. + pregnancy >>共 132
prevent 15.89%
terminate 12.88%
end 10.37%
avoid 3.51%
reduce 2.84%
have 2.84%
hide 2.51%
abort 2.17%
announce 2.01%
carry 2.01%
maintain 1.34%
maintain + n. >>共 867
innocence 4.21%
control 3.78%
tie 3.11%
relation 2.70%
order 2.50%
contact 2.47%
security 1.56%
stability 1.39%
sanction 1.33%
peace 1.24%
pregnancy 0.06%
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