1. There is a dispute about why a firstborn girl is "a good sign for boys."
2. Rav Chisda preferred girls over boys.
3. There is a dispute about what the verse means when it says, "And Hashem blessed Avraham with everything."
4. There is a dispute about whether it is more important to support boys or to support girls.
5. The Gemara discusses whether a person can give something to a fetus.
A BIT MORE
1. Some say that this is because she helps her mother raise her younger brothers. Some say that this causes people not to cast an evil eye on this family.
2. This was because his son-in-laws (Rava and Rami bar Chama) were the leaders of the generation (Tosfos).
3. Rebbi Meir: The blessing was that he did not have a daughter. Rebbi Yehudah: The blessing was that he did have a daughter.
4. Rebbi Meir: It is more of a Mitzvah to support boys, since they learn Torah. Rebbi Yehudah: It is more of a Mitzvah to support girls, to ensure that they do not become denigrated (as it is far more denigrating for girls to ask for charity).
5. Rav Huna: A person cannot give ownership of an item to a fetus. The Gemara notes that Rav Huna disagrees with our Mishnah (see Daf 140:4 above).