Quickening is defined as the first movements of the fetus felt in utero. It occurs from the eighteenth to the twentieth week of pregnancy. Movements have been felt as early as the tenth week and in rare cases are not felt during the entire pregnancy. The mother becomes conscious of slight fluttering movements in her abdomen which are due to movements of the fetus. The physician is often able to hear the fetal heart for the first time. If the fetus is born at this point, it may make a few efforts to breathe, but its lungs are insufficiently developed to cope with conditions outside the uterus and it invariably succumbs within a few hours.
Quickening is a term derived from an idea prevalent many years ago that at some particular moment of pregnancy life is suddenly infused into the infant. At the time this notion was in vogue, the first tangible evidence of intrauterine life lay in the mother's feeling the baby move, and the conclusion was only natural that the infant "became alive" at the moment these movements were first felt. We now know that the infant is a living organism from the moment of conception, but the old term "quickening" is still used in obstetric terminology.
Many fetuses, although alive and healthy, seem to move about very little in the uterus, and, not infrequently, a day or so may pass without a movement being felt. Inability to feel the baby move does not mean that it is dead or in any way a weakling but, in all probability, that it has assumed a position in which its movements are not felt so readily by the mother. Moreover, it is a well-established fact that the fetus sleeps in the uterus, and it seems likely that the periods of active movement and quiescence which the mother notices correspond to the phases of somnolence and wakefulness. Should three or four days pass without movements, the physician should be asked to listen for the fetal heart sounds. If these are heard, it means that the fetus is alive and presumably in good condition. Women occasionally misinterpret movements of gas in the intestines as motions of a baby and imagine themselves pregnant. Therefore, the patient's statement that she feels the baby move cannot be regarded as absolute proof of pregnancy.
The woman should be informed about the importance of documenting the first perceived fetal movement in order to help confirm dating of the pregnancy. Use of a fetal growth and development chart may also be helpful.
At 12 weeks gestation the baby is about three inches long and weighs one ounce. The baby is beginning to open and close its mouth and move its hands, legs, and head.
At 16 weeks gestation baby's length is six to eight inches, weight is about six ounces, and organs such as the heart and lungs are formed.
At 20 weeks gestation, length is eight to 12 inches, weight is one-half of one pound, and the activity of the fetus increases moving side to side or turning around.
At 24 weeks gestation the baby is fully formed, with wrinkled skin, about 14 inches long and one and one-half pounds. The baby still needs to grow and fully develop vital organs such as lungs and brain.
At 28 weeks, length is 15 inches, weight is two to three pounds, bones are getting harder, and the woman may feel the baby kick and move more.
At 32 weeks, length is 18 inches, weight is about five pounds, baby can open its eyes, may turn around in the womb and stay in the new position for the rest of pregnancy.
At 36 weeks, length is 19 inches, weight is about six pounds and gains on-half pound each week.
At 40 weeks the baby is at "full term" (will have gone through the full length of pregnancy).