This article is an excerpt from our Sefer
The night of Rosh Chodesh is an auspicious time for intimacy. Even according to Kabbalah, it is permitted for a Torah scholar to have intercourse on the night of Rosh Chodesh, even during weekdays. [This does not mean that he is obligated to have intercourse on Rosh Chodesh, but rather simply that it is an auspicious time for intimacy, and therefore it is best for one to schedule his minimum required Onah for this night.]
Which days of the week are most auspicious for intimacy?
Some Poskim write that those who have intimacy during weeknights [i.e. most people today, whose Onah is twice a week] are to do so on Wednesday night [and onwards, and not on Sunday-Tuesday]. This, however, only applies if the wife is able to conceive.
 M”A 240:3; Sha’ar Hamitzvos Bereishis; Sha’ar Hakavanos p. 3; Peri Eitz Chaim 16:1118:18; Beri Haiytiv 240:3; M”B 240:7; Kaf Hachaim 240:2; Piskeiy Teshuvos 240:4
 M”B 240:7; Sha’ar Hatziyon 240:3; Piskeiy Teshuvos ibid; Vetzaruch Iyun if it may be chosen in place of Friday night or in addition to Friday night. Perhaps this matter is left to the discretion of the person and he may choose to do it instead of or in addition to Friday night.
 Yifei Laleiv 2; Ben Yehoyada Niddah 38a; Meiy Da’as 240:20; Sheyikadesh Atzmo 8 footnote 2
 The reason: This is done in order so she should give birth on Sunday, or on a later day of the week, and not on Shabbos. [ibid]