"Love Lives On," the "ABC Monday Night Movie" at 9 on Channel 7, starts off as a film about teen-age drug abuse, turns into a film about facing terminal cancer and then becomes the story of choosing a difficult and perilous pregnancy over a comparatively humane abortion. Wife beating and alcoholism are thrown into the prob-drama stew for good measure. At every turn, though, the movie is consistent on one point: It's all fairly appalling slush.

Two actors nominated for Oscars this year, Christine Lahti and Sam Waterston, waste their time and talents as the parents of a 15-year-old girl with enough woes for three TV movies. April Smith's flamboyantly shameless script, "drawn from actual events," according to a disclaimer (that's the TV-movie equivalent of James Bond's license to kill), thwonks the heroine around from one crisis situation to another before the film finally settles down to its central dubious dilemma. Larry Peerce, the director, gives the appearance throughout that he would be more at home in charge of a cattle drive.

As the film opens, we are made aware that poor Susan, played by Mary Stuart Masterson, is what you call heavily into the drug scene; she swipes old "Grampy's" medication, and the drugs that her grandmother, a nurse, lifts from the hospital and brings home with her, so she and a friend can groove to excess on Rod Stewart records. She is shipped off to a drug treatment center and must fall off a canoe and nearly drown in order for Smith to set up the cancer plot line. Why the film had to take such a roundabout route to its own premise is one of life's shrimpy little mysteries.

No one tells Susan that chemotherapy will cause her hair to fall out, and she's apparently missed all 975 TV movies to have dealt with this condition, so she gets more hysterical over the hair loss than the cancer, and Peerce shoots the scene with lurid "Exorcist" zeal. A nice boy named Brian (Ricky Paull Goldin) falls in love with Susan but wouldn't you know, he turns out to be a spineless coward who faints at the sight of a needle and runs away to a drag strip when he learns his girlfriend is pregnant by him.

Susan is told by doctors that if she chooses to have the child, she will effectively be shaving six months off her own life and that there is a strong chance the child will suffer birth defects or other debilitating complications. Nevertheless, she elects to have the child. But writer Smith doesn't give her any eloquent or even persuasive dialogue to support the decision. Instead she has Susan say, "Why don't I just go for it and have the kid?" and explain her choice with the all-purpose justification "I want to."

When during the later weeks of pregnancy she is put on morphine and is told the child will probably be born addicted to it, she says the equivalent of, oh fiddledeedee. This picture will certainly please that element of the political spectrum holding that no matter what the danger to mother or child, it is imperative that all conceived babies must-must-must be born. Earlier in the film, it is stated that Susan was under the impression that chemotherapy made her sterile and thus unable to conceive. However, there is no direct reference to birth control by any of the characters, nor even use of a euphemism like "precaution," so as to remind impressionable young viewers that there are alternatives (TV programs maintain a pathological fear of the subject of birth control and networks refuse to accept contraceptive advertising, no matter how discreet and tasteful). Instead, the idea of being a doomed pregnant teen-ager is made to seem gloriously romantic, and the word "miracle" is thrown around with ignorant abandon.

Simply terrible as the whole thing is, Lahti redeems every scene of the film in which she appears with her wonderfully bright, level-headed naturalism, simply and thoroughly a joy to watch. Waterston, for his part, never reaches even borderline credibility as Bernie Everyguy, recovered alcoholic; for the effete Waterston, a blue collar is a yoke. Goldin seems an intelligent, imaginative young actor, able to leap yawning cliche's at a single bound, and as Susan, Masterson makes an affectingly insistent struggler out of a character written more along the lines of a selfish brat.

"Love Lives On" drags on, despite the efforts of its cast, and the audience's cues to weep are as blunt as orders barked by a drill sergeant. Cranky reviews are really insufficient punishment for movies like this. Perhaps fines could be levied in such cases, or the producers sued for the loss of two hours by viewers who stumble into such things hoping merely for a good cry but getting at best a bad one.