http://revach.net/article.php?id=3415

Section: Halacha   Category: Tshuvos
Rav Shmuel Vosner: Stopping After Eight Children?
Rav Shmuel Vosner was asked (Shevet HaLevi 4:161) if a 44 year old person with eight children must still have children or he may stop. One of his concerns was that the local school had mixed classes until the age of 14.  The man's wife on the other hand claimed that she would undertake the burden of the chinuch and they can raise frum children even in that environment.

The questioner's justification was based on, among other things, a Tshuvas Pnei Aharon that says that if proper Chinuch is hard to come by where you live, then it is sufficient to be Mikayem the Mitzva of Pru U'Rivu with a son and daughter and you need not fulfill the mitzva of "BaBoker Tanach..." (the mitzva to have as many children as possible).  He learns this from Chizkiya (Brachos10a) who became deathly sick because he refused to marry and have children since he knew B'Ruach HaKodesh that his children would be Reshaim (Menashe).  The gemara specifically says that he wasn't Mikayem the mitzva of Pru U'Rivu and doesn't say anything about "BaBoker Tanach..."

Additionally the questioner brings the Chofetz Chaim who was quoted as saying, "who said it is a bracha to have children if you don't know how they will turn out?"

Rav Vosner says that he wouldn't typically answer this question but there is a mitzva to help those who are mistaken.  He didn't see the Tshuvas Pnei Aharon but the proof from Chizkiya is not valid for a number of reasons.  Moreover even if it were, says Rav Vosner, Chizkiya knew with 100% certainty that his children would be Reshaim.  Nowadays, there is no situation where we cannot say for sure how are children will turn out. 

As for the quote from the Chofetz Chaim, says Rav Vosner, these are not things that we can rely on to pasken Shailos when we don't know the background to this comment.

Important Note: We try to convey the Tshuva to the best of ourability. We admit that our understanding may not be accurate. One should learn the tshuva to verify the accuracy of our interpretation.  Please also understand that this Tshuva may not be the final word on thistopic. One should consult a Rav before drawing any conclusions.