You are very wrong and provided no facts in your post and a Catholic is not excommunicated for committing a mortal sin, that's what confession is all about. I suspect that you are not Catholic. I do not need to review my Catechism, thank you.
Here is the Canon Law (notice the word "procures")
OFFENSES AGAINST HUMAN LIFE AND FREEDOM
Can. 1397 -- One who commits homicide or who fraudulently or forcibly kidnaps, detains, mutilates or seriously wounds a person is to be punished with the deprivations and prohibitions mentioned in can. 1336 in accord with the seriousness of the offense; however, homicide against the persons mentioned in can. 1370 is punished by the penalties specified there.
Can. 1398 -- A person who procures a successful abortion incurs an automatic (latae sententiae) excommunication.
[The Latin original reads: Can. 1398 -- Qui abortum procurat, effectu secuto, in excommunicationem latae sententiae incurrit.]
An excommunication is the heaviest spiritual sanction the Church can render. So long as it is in force, it bars the excommunicated person from the church community and from receiving most of the sacraments, as well as from all public associations affiliated with the Church. An automatic (or "latae sententiae") excommunication is an especially severe penalty. The nine or so latae sententiae excommunications in the Code are reserved for use against certain things the Church particularly wants to deter, like assaulting the pope (can.1370) and priests divulging matters heard in the confessional (can.1388). Most excommunications can only follow a tribunal trial (can. 1425, §1, 2°). But latae sententiae penalties operate like a bill of attainder in that there is no "process" for their imposition--the fact that the person voluntarily performed the proscribed act, in the absence of some exception provided in the law, means the penalty is incurred. An excommunication can usually be lifted by the local bishop (the "local ordinary") and sometimes by a priest during confession (can. 1354-1357).
The canons of the 1917 and 1983 Codes apply to all direct abortions. Abortions incident to otherwise lawful medical care that is required to save the life of the mother (e.g. chemotherapy, hysterectomy of a cancerous uterus) are given an interpretive exception from the rule under the priciple of "double effect."
As in all penal laws there are qualifications as to who is subject to a law--Canon 1321, and following, of the 1983 Code makes such provisions.
Irregularity
From the earliest days of the Church, men who had shed human blood, no matter how justifiable or blameless the act may have been, were excluded from entering the priesthood (e.g., Decretum Gratiani by Pope Innocent I in the year 404). This traditionally embraced abortion as a form of homicide. However, in 1211, Pope Innocent III issued the decree Sicut ex, which limited the irregularity incurred from abortion to abortions involving a fetus that was not "animated" or "ensouled." This exception was subsequently abrogated as both of the modern codes have provisions that apply to all abortions (can. 985, §4 in the 1917 Code, and can.1041, 4° in the 1983 Code).
And the Catechism:
http://www.scborromeo.org/ccc/p3s2c2a5.htm#2270Why does this whole discussion remind me of the Pharisees in the times of Paul? Or even more, the time following the handing down of the Commandments and the subsequent Levitical Laws?
A person who committs a mortal sin is fallen from the state of grace and into the state of mortal sin and is not elligible to receive any sacrament but confession. He is out of communion with the Church. This is what I was talking about, not formal excommunication. That should have been made clear to you. And you know it is a mortal sin to assist or give consent to a mortal sin. What do you think voting for the murder of human children is if not consent to those mortal sins of murder?