Feldman et al (2007) assessed oxytocin and cortisol levels during and after pregnancy and found that

Feldman measured plasma oxytocin from sixty-two pregnant women during their first trimester, third trimester, and the first postpartum month. Feldman et al (2007) assessed oxytocin and cortisol levels during and after pregnancy and found that  higher maternal oxytocin levels were associated with higher levels of affectionate caretaking and attachment related thoughts.

Since a haploid cell only contains one set of chromosomes, there would be a problem that would occur during meiosis i. the homologous chromosomes could not line up because of the lack of a second pair of chromosomes in the nucleus of the cell.