use of PGD to guarantee a fifth child's gender

The consensus of poskim is that if that there is a need for IVF anyway, PGD can be used to determine the gender. However, if the couple is naturally fertile and there is no need for IVF, to utilize PGD just to ensure gender is not allowed, on account of the halachic issues related to IVF procedure. (See Nishmat Avraham, E.H. 1:1[5], citing Rav S.Z. Auerbach zt"l). In situations where there is serious concern for the psychological welfare of the mother, confirmed by the attending psychological therapist, who recommends PGD as part of the therapeutic treatment – it is permissible.

See additional sources at #785, #4431.

Kol Tuv,
Meir Orlian