While child abuse is universally condemned and many people militantly crusade to protect the rights of the unborn, no one cries out about the abuse done to children -- both in the womb and after birth -- by smoking adults.

Physicians have long cautioned pregnant women to be sparing in their use of alcohol, certain drugs, caffeine and diagnostic X-rays for fear of injuring the fetus. Only recently have they extended these warnings to cigarette smoking.

Increasing numbers of scientific studies show that regular smoking injures the fetus in several ways. For example, within minutes, each cigarette puff introduces carbon monoxide, which reduces the blood's ability to carry oxygen, and nicotine, which constricts the blood vessels carrying blood to the baby. Together, they deprive the child of oxygen. If this is repeated often enough, it could irreparably damage the fetal brain.

Nicotine also crosses from the placenta to the fetus, where it stimulates the heart and depresses the lungs. When pregnant women smoked only two cigarettes, their fetuses' heart rate accelerated; this was accompanied by abnormal breathing-like motions, a sign of fetal distress.

These findings assume more serious overtones if one multiplies the five puffs per cigarette inhaled by the average smoker by 20 (the number of cigarettes in a pack-a-day habit) and then by 270 (the number of days for gestation). This means that the fetus of a smoking mother is subjected to at least 27,000 physiochemical insults, beginning with the initial phase of growth and development when the early stages of rapid cellular division are most vulnerable, and continuing throughout its entire uterine life.

Animal experiments show that the byproducts of tobacco smoke can upset fetal metabolism and the endocrine gland system, and even damage the unborn's genes.

All of this smoke-caused damage may explain why smoking mothers have a higher incidence of spontaneous abortions, stillbirths and premature deliveries than nonsmokers. The babies of heavy smokers are apt to be smaller at birth, more susceptible to neonatal diseases and at increased risk of dying in early infancy.

They also have a tendency to be born with cleft palate and hare lip and later on may exhibit developmental difficulties such as shortness in stature, lower scores in social adjustment, behavorial problems, impaired reading abilities, hyperactivity and mental retardation.

Constantly exposing a child to the cigarette smoke of others (so-called "passive smoking") also can cause health problems, including an increase in ear, nose and throat infections, bronchitis, pneumonia, asthmatic attacks, and a decreased lung efficiency. The frequency and severity of these conditions are directly related to the number of smokers in the household and, in particular, the number of cigarettes smoked by the mother.

Nicotine is also known to be passed on to the infant in breast milk and absorbed from the smoke-filled surroundings. The more the mother smokes, the more nicotine the child absorbs and the greater its potential for damage to the lining of the infant's nose, mouth, stomach and lungs.

Sidestream smoke, the fumes emanating from the lighted tip of a cigarette held in the mouth or buring itself out in an ashtray, add to the problems because it contains cancer-causing chemicals.

The Environmental Protection Agency estimated that between 500 and 5,000 cases of lung cancer appear annually in nonsmokers as a result of passive inhalation.

Parents who smoke perpetrate yet another wrong upon their children. As role models, they add their influence to that already exerted by peer pressure, peer acceptance and tobacco advertising in creating an environment conducive to smoking. As a result, the young find it especially difficult to resist starting the habit.

Parents must share the responsibility for the 3,000 to 5,000 American children who light up for the first time each day, most of whom will continue the habit into adulthood.

Inherent in a household of smokers is the heightened danger of accidental fires. Many of these are started by young children who, with their notorious fascination with fire, will be tempted to imitate the match-striking and flame-producing gestures of their elders. The tragic and agonizing consequences of this are reflected in the National Safety Council's estimates for 1983 that one third of the 5,000 home fire fatalities were attributable to smoking.

Although no statistics are available for the huge number of near-fatal burns or permanently disfiguring scars, all hospital burn centers will attest to the dominant role smoking plays in providing them with a constant source of victims.

Realizing all this, what parents can justify persisting in a habit so threatening to their young? Certainly, the variety and magnitude of its hazards should serve as enough incentive for them to quit.

During childbearing, the mother, by this single act of self-discipline, has it within her power to minimize the risk of a complicated pregnancy or of imposing lifelong physical and mental handicaps upon her child.

These warnings are not solely the concern and responsibility of mothers and fathers. Members of the clergy, PTAs, educators and legislators should all recognize the link between smoking and various prenatal, neonatal and juvenile disorders.

Child abuse comes in many forms. Although the hazards of smoking may not appear as dramatic or as obvious as the others forms of abuse, they are nevertheless just as capable of maiming and destroying the young. In view of the fact that more than 50 million Americans smoke, this form of abuse may well be the most pervasive and child-damaging of them all.