An extensive body of research demonstrates that children increase the stability of marriage, but it is unclear whether the same is true for cohabitation. Marital stability theories often assume fertility is intended, which is less likely to be the case for cohabiting births. Using the 2002 National Survey of Family Growth, we find that intended and disagreed-upon pregnancies (but not unintended pregnancies) reduce the risk of dissolution relative to women who have no pregnancy or birth. Relative to nonfertile couples, all pregnancies increase the risk of marriage over staying cohabiting, but there is little difference in the odds of stability or transitions after birth. However, relative to an intended birth, having an unintended or disagreed-upon birth increases the risk of dissolution. These findings suggest that normative pressures influence the union behaviors of cohabitors during pregnancy, whereas selection processes and rational choice considerations play a greater role after a birth.