Why were the Matriarchs barren? Bereishis Rabbah (45:4)

update - added Bereishis Rabbah (45:5) and Yevamos (64a)

Bereishis Rabbah (45:4): Why were the Matriarchs barren?... Because G-d has a strong desire for their prayers and their requests.... R’ Chanina answered, So that they would be dependent and attached to their husband in spite of their beauty. Rav Chiya bar Abba answered, So that they would spend most of their lives without being burdened (i.e., Exile should be delayed). Rav Meir said so that their husbands should get pleasure from them because when a woman becomes pregnant she becomes ugly and lacks grace. 

For the 90 years that Sara did not have children she was like a bride in her canopy. When aristocratic women came to ask how she was she would say, “Go ask about the welfare of that unfortunate woman [Hagar]. And Hagar would say to them, Sarai my mistress in a hypocrite. She appears as a righteous woman but how could she be righteous. Look at how many years she has been married and hasn't gotten pregnant. In contrast I got pregnant the first time.” [Rashi 16:4 cites this medrash to explain what Hagar did to belittle Sarah]. Sarah replied, “Should I argue with this woman? I will complain to the master.

Bereishis Rabbah (45:5):  AND SARAI SAID UNTO ABRAM: MY WRONG (HAMASI) BE UPON THEE (XVI, 5). R. Judan explained this in R. Judah's name: Thou wrongest me with words, since thou hearest me insulted yet art silent.4 R. Berekiah explained it in R. Abba's name: I have a grievance against thee. For imagine two men incarcerated in prison, and as the king passes one of them cries out, ‘Execute justice for me!’ The king orders him to be released, whereupon his fellow-prisoner says to him, ' I have a grievance against you, for had you said, " Execute justice for us," he would have released me just as he has released you; but now that you said, "Execute justice for me," he released you but not me.’

Similarly, hadst thou said, ' We go childless,’ then as He gave thee a child so would He have given me; since, however, thou saidest, And I go childless (Gen. XV, 2), He gave thee a child but not me. This may [also] be compared to two people who went to borrow seed from the king. One of them asked, ' Lend me seed,’ and he ordered, ‘Give it to him.’ Said his companion to him, ‘I have a grievance against you. Had you asked, "Lend us seed," he would have given me just as he gave you; now however that you said, " Lend me seed," he has given you but not me.’ Similarly, hadst thou said, ‘Behold, to us Thou hast given no seed,’ then as He gave thee so had He given me. Now however that thou didst say, ’Behold, to me Thou hast given no seed ' (ib. 3), He gave to thee but not to me.

R. Menahema [Nehemiah] said in R. Abin's name: She scratched his face.1 The Rabbis said: Women are said to possess four traits: they are greedy, eavesdroppers, slothful, and envious. Greedy, as it says, And she took of the fruit thereof, and did eat (ib. III, 6); eavesdroppers: And Sarah heard in the tent door (ib. XVIII, 10); slothful: Make ready quickly three measures of fine meal (ib. 6); envious: Rachel envied her sister (ib. XXX, 1). R. Joshua b. Nehemiah said: She is also a scratcher and talkative. A scratcher:  AND SARAI SAID UNTO ABRAM: MY SCRATCH BE UPON THEE. Talkative: And Miriam spoke against Moses (Num. XII, 1). R. Levi said: She is also prone to steal and a gadabout. Prone to steal: And Rachel stole the teraphim (Gen. XXXI, I9). A gadabout: And Dinah went out (ib. XXXIV, 1).

THE LORD JUDGE BETWEEN ME AND THEE (UBENEKA). R. Tanhuma said in the name of R. Hiyya the Elder, and R. Berekiah said in R. Eleazar's name: Whoever plunges eagerly into litigation does not escape from it unscathed. Sarah should have reached Abraham's years, but because she said, THE LORD JUDGE BETWEEN ME AND THEE, her life was reduced by forty-eight years. R. Hoshaya said: Binka (thy son) is written.1 Seeing that it is already written, And he went in unto Hagar, and she conceived, why is it further stated, Behold, thou wilt conceive (ib. 11)?2 This, however, teaches that an evil eye took possession of her and she miscarried.3 R. Hanina observed: Had the prophet Elisha told her that by the Holy Spirit, it would have sufficed her.’

In contrast see Yevamos(64a):

The other replied: Isaac was barren.If so,Abraham also was barren!— That text is required For a deduction in accordance with the statement of R. Hiyya b. Abba. For R. Hiyya b. Abba stated in the name of R. Johanan: Why were the years of Ishmael counted? In order to determine thereby the years of Jacob. 

R. Isaac stated: Our father Isaac was barren; for it is said, And Isaac entreated the Lord opposite his wife.It does not say ‘for his wife’ but opposite. This teaches that both were barren.If so, And the Lord let Himself be entreated of him should have read, And the Lord let Himself be entreated of them!— Because the prayer of a righteous man the son of a righteous man is not like the prayer of a righteous man the son of a wicked man. 

R. Isaac stated: Why were our ancestors barren? — Because the Holy One, blessed be He, longs to hear the prayer of the righteous. 

R. Isaac further stated: Why is the prayer of the righteous compared to a pitchfork? As a pitchfork turns the sheaves of grain from one position to another, so does the prayer of the righteous turn the dispensations of the Holy One, blessed be He, from the attribute of anger to the attribute of mercy. 

R. Ammi stated: Abraham and Sarah were originally of doubtful sex for it is said, Look unto to the rock whence you were hewn and to the hole of the pit whence you were digged, and this is followed by the text, Look unto Abraham your father, and unto Sarah that bore you.

R. Nahman stated in the name of Rabbah b. Abbuha: Our mother Sarah was incapable of procreation; for it is said, And Sarai was barren; she had no child,she had not even a womb.