MOTHERS ON TRIAL; The Battle for Children and Custody. By Phyllis Chesler. McGraw-Hill. 651 pp. $22.95.

I MOTHERS ON TRIAL, Phyllis Chesler tackles a problem of considerable magnitude: the increasing likelihood that a fit mother will lose her child to its father in a custody fight. Whether or not one accepts Chesler's skewed sample, which erroneously suggests that the mother who wins custody is rare, the problem is real and wrenching.

Ironically, the problem stems in part, as Chesler notes, from misguided feminist efforts. Rather than expend their energies on, say, improving the record of deadbeat fathers who don't pay child support, feminists fought instead to end alimony and to bind courts to sex-blind custody determinations. The result is even shorter rations for divorced mothers and, as Chesler points out, a greater likelihood that the father who sues for custody will win, frequently to the detriment of the child.

The plight of these embattled women and children is so grim that even a dispassionate report on the situation would have been searing. Dispassion, however, is not Chesler's forte. Because the real story is lacking somewhat in drama, Chesler resorts to exaggeration and sometimes to misrpresentation, leaving her open to criticism for sloppy scholarship. Serious errors permeate her recitaion of the development of the law in this area. The best interests of the child, for example, were not, as Chesler states, "always seen as synonymous with paternal rights." To the contrary, at least until recently. Similarly, many of the reports of legal cases are incomplete or otherwise misleading; frequently Chesler merely repeats reports of cases from sources of dubious objectivity, e.g., militant feminist publications.

The undifferentiated outrage that Chesler brings to the recounting of each of her subjects' custody battles (60 mothers are included) is similarly destructive to the book's effectiveness. Too many of the women appear to even the most sympathetic reader to raise issues of fitness. Two of the many lesbian mothers Chesler includes, for example, were not merely openly gay but had together made and distributed a film about their and their children's unique arrangement titled "Sandy and Madeleine's Family." Quite possibly these women were treated unfairly in court, but one can imagine a not wholly frivolous argument being advanced by the custody-seeking fathers.

Indeed, so uniformly enflamed is Chesler's book that one begins after a time to abreact uncomfortably. Many of the women who lost custody because their ex-husbands successfully cast doubt on their mental health, for instance, do begin to sound a bit dotty. "(He) was always secretive," the author quotes one mother describing her ex-husband. "For instance, whenever he went to the dentist, he refused to let me see the inside of his mouth."

Nor is Chesler's effectiveness helped by her frequent bizarre interpolations, e.g., "Abortion was, and still is, seen as an act of female violence against a helpless male fetus and against the fetus as private (male) property." "The unspoken passion in Gone with the Wind (as in so many other films) is that of father- daughter incest . . . . Bonnie is Rhett's child bride and Rhett's 'own' little female self." Or the following, which is found in the middle of Chesler's interview with a mother who is a topless dancer: "Naked women dancing are our fertility goddesses -- held in contempt. Nailed him to a cross, caged her genitals in shame. Continuous red neon breasts: obscene adoration, sacred love."

In the midst of this morass, the excellent points Chesler makes tend to be buried. Permit me to disinter them: Many divorcing fathers threaten custody suits with no desire to have the child but simply because the mother, out of fear of losing, will lower or abandon her request for child support in return for assured custody. Many mothers in custody battles are ill-served by the legal system, frequently because they are economically unable to enforce their rights; usually it is the child's father who creates that economic disadvantage by refusing to pay court-mandated support. Feminists have fought the wrong legislative fights. Societal standards would be laughable if they weren't so angering -- the father who changes one diaper is a hero; the mother who misses one PTA meeting is unnatural. That double standard works against mothers in custody fights as does a more familiar double standard -- a woman who has not been thoroughly circumspect both during and after marriage may find herself in real danger of losing her children. Judges frequently impose other standards of breathtaking arbitrariness. Most important, children are suffering. All of these matters should be addressed -- by the courts and the legislature, and by society. Alas, the use of Chesler's book as a weapon for change is limited; those opposed to its laudable ends may too easily employ the book's flaws to defuse, refute, and dismiss it.