In The Country Girls, The Girl with Green Eyes and Girls in Their Married Bliss, O'Brien illustrates the high cost to girls and women of living in an Irish society plagued with stagnation: the lack of options is suffocating to women. In The Country Girls, Cait and Baba suffer the oppression of a stifling Irish convent girls' school—a cold, claustrophobic environment that seems to belong in another century (one might compare it to the Lowood School in Jane Eyre). They are only liberated when they manage to get expelled.

In the ironically titled Girls in Their Married Bliss, Baba and Kate are both unhappily married, Baba to a social climbing rich man and Kate to Eugene. Kate's only escape is through her child and her continuing desire for romance, which leads to an affair. Either way, in a bleak marriage or in the divorce that follows, Kate is stifled—and increasingly given to blaming herself for situations that offer her few options.

O'Brien's trilogy shows how a society that refuses to move forward—in its laws, conventions, and narrow-mindedness—can profoundly limit a woman's choices.

In The Girl with Green Eyes, Cait, now called Kate, cannot even make choices over her own body: in patriarchal Irish society this is fought out between erstwhile lover Eugene and Kate's father. Both Kate and Baba search for satisfying romantic love and selfhood in an Ireland that both legally and culturally denies woman's rights. One of O'Brien's themes is the difficulties this social context causes for women trying to find love.

The trilogy is an exploration of love in a society that suffocates women, but it is also centrally about loss: loss of mothers, loss of love, loss of God, loss of dreams. O'Brien herself states in a 1982 interview with Shusha Guppa that

my work is concerned with loss as much as with love. Loss is every child's theme because by necessity the child loses its mother and its bearings. And writers, however mature and wise and eminent are children at heart. So my central theme is loss—loss of love, loss of self, loss of God . . . .