It is of extreme practical importance to be able to recognize a pregnancy at all periods. The _subjective symptoms_ of the first half are—amenorrhœa, morning sickness, irritability of the bladder, discomfort and swelling of the breasts, enlargement of the abdomen and quickening; but the appearance of any or all of these phenomena is not to be regarded as conclusive, but merely as a presumption that pregnancy exists. Either through ignorance, intent to deceive, or from pathological conditions, any or all of these symptoms may be present, but not until the tenth week are the changes in the uterus sufficiently definite to confirm a diagnosis unless the circumstances are especially favorable. =Amenorrhœa.=—Cessation of the menses is practically invariable in pregnancy. One or two periods may occur after conception, but care must be used to exclude other causes of hæmorrhage. Sudden cessation of the periods in a healthy woman of regular habits who is not near the menopause, is strongly suggestive of pregnancy. Why a developing ovum causes an immediate arrest of menstruation is not understood. Amenorrhœa may occur in consequence of chlorosis, heart disease, hysteria, tuberculosis, fright, grief, and some forms of insanity; a change from a low to a high altitude, or an ocean voyage not infrequently causes the flow to remain absent for one or more months. In addition to its value as a presumptive symptom, the amenorrhœa affords a common and convenient method of estimating the date of confinement. The method is fallacious but practical, and will be discussed later. =Morning Sickness.=—This symptom is not invariable. It is most frequent in primiparas, but not so likely to occur in subsequent pregnancies. It usually appears about the second month, shortly after the first period missed. It varies in intensity. Some women have a little nausea on arising and no further trouble during the day, others are nauseated and vomit either on rising or after the first meal, and yet others after each meal; but the general health is not ordinarily affected and the tongue remains clean. Some cases are of extreme severity (hyperemesis) and will be discussed elsewhere. The morning sickness is probably toxic in origin. It must be remembered that chronic alcoholism is accompanied by morning sickness, but with it the tongue is furred. =Irritability of bladder= is shown by a frequency of urination. It is caused by the congestion and stretching of the tissues that lie between the uterus and bladder and hold them in relation to one another. After the third month an accommodation is established and the symptom does not reappear until late in pregnancy, when the pressure of the heavy uterus tends to keep the bladder empty. If especially annoying, this irritability may be much relieved by putting the patient in the knee-chest position night and morning.