There is a Halachic option that says if there are otherwise 9 adult (above bar mitzvah age) Jewish males, an underage (pre bar mitzvah) Jewish male can be counted to make a minyan (which normally requires 10 adult males). My question is, if a Jewish woman is pregnant with a male baby/fetus, and there are 9 adult Jewish men present, can her child be counted as a minyan with her present?
The Shulchan Aruch (Orach Chayim 55:4) talks about adding a Katan to a minyan:
יש מתירים לומר דבר שבקדושה בתשעה וצירוף קטן שהוא יותר מבן שש ויודע למי מתפללין ולא נראין דבריהם לגדולי הפוסקים וה"ה דעבד ואשה אין מצטרפים. הג"ה: ואפילו על ידי חומש שבידו אין לצרפו מיהו יש נוהגים להקל בשעת הדחק [הרא"ש ומרדכי והגהות מיימוני פ"ט מהלכות תפילה]
There are those who allow the saying of holy prayers (i.e., ones that need a minyan) with nine men and a Katan who is over six years old and knows to Whom we pray, but this opinion is not that of the great Poskim*. And the same is true that a slave and a woman can't be counted towards a minyan. Rema: and even with the Chumash in his hands we don't count him, however there are those who are lenient and count him (even without the Chumash, according to the Mishna Berura) in a time of need [Ru"sh Mordechai and Hagahos Maimonios, chapter 9 of Hilchos tfila]
*This is a reference to the Rambam and Tur, per the Gr"a on this seif.
The translation and emphasis is mine, as is anything in parentheses ().
So, not only would a fetus not count, but no kid under the age of six counts, and even then only according to the second opinion in the Rema, in times of need.
Although this is mostly unrelated, the Chidush the Rema adds by saying 'even if he's holding a Chumash we don't count him' is that in some (very specific) cases**, we count a Sefer Torah as a person to make a minyan, that will not help and 'be mitz'taref' with the Katan to make the tenth man.
**Specifically, being the last man needed when making a leap year, per the Gr"a on this Seif.