“The mitzvah of pru urvu (having children) is a very important mitzvah; in fact, it is the very first mitzvah mentioned in the Torah. In the words of the Alter Rebbe, the first mitzvah of the Torah is that one Jew should make another Jew. However, unfortunately there are people who face grave challenges in fulfilling this mitzvah, and have great difficulty receiving Hashem’s blessing to have children. It is important to help such people as much as possible and to daven for them on every occasion, especially at opportune times for such tefillos. The Chofetz Chaim wrote an entire sefer—called Shem Olam— for couples who have not been blessed with children yet. In his sefer he includes words of chizuk, telling them how—despite their tribulations—they can retain their bitachon (trust) in Hashem, confident that whatever Hashem does is for the good, and believe that G-d willing, He will answer them.” via halacha2go.com