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Separate evidence produced by the mother from evidence identifying the fetus. The classical presumptive, probable and positive grouping expresses increasing diagnostic confidence; it is not a numerical probability scale.

Presumptive signs include missed menstruation, nausea or pregnancy-associated vomiting, breast enlargement and tenderness, changes in the areola, urinary frequency and the mother's sensation of fetal movement, traditionally called quickening. Each can have another explanation. Amenorrhoea may result from illness or endocrine disturbance; abdominal enlargement can arise from a pelvic mass, ascites or other causes. A report of movement is not equivalent to movement detected independently by the examiner.

Probable physical signs include a progressively enlarged uterus with the appropriate change in contour, softening of the cervix and uterine tissues, increased vascularity and colour change of the genital mucosa, and intermittent uterine contractions. Ballottement is the rebound of a movable object within fluid when it is displaced: in the right clinical setting it supports a gravid uterus, but the physical phenomenon alone does not identify a living fetus. A vascular sound heard over the uterus follows the maternal circulation and is not the fetal heartbeat.

Positive evidence available to the 1865 examiner was a fetal heartbeat heard with a stethoscope, unmistakable fetal movements appreciated during examination, and identification of fetal parts. Repeated examination as pregnancy advances strengthens their interpretation. The examiner should compare the perceived heartbeat with the maternal pulse rather than accept any abdominal sound as fetal. These findings generally become useful later than the earliest symptoms, so their absence early on does not exclude pregnancy. The mother’s quickening remains a symptom; independently established fetal movement is a different kind of evidence.

Modern additions. Human chorionic gonadotropin testing can detect pregnancy-related tissue before the classical physical signs become conclusive. A positive test does not establish location or continuing viability: it can occur in ectopic pregnancy and must be interpreted in context. Ultrasound can establish location and show an embryo or fetus with cardiac activity. Very early uncertain findings may require repeat assessment rather than a premature conclusion. These technologies are later developments, not signs that an 1865 candidate could have obtained. ^{[ref] [ref]}

Vomiting is a coordinated nervous motor act that can be initiated from the digestive system, circulating emetic substances, the vestibular system, or higher and lower brain pathways. A cause need not lie in the stomach.

Local causes include irritant food or poisons, gastritis, gastroenteritis, gastric outlet obstruction and intestinal obstruction. Chemical irritation, inflammation or distension activates visceral sensory pathways, notably afferents of the vagus nerve, which relay to the medulla oblongata. In obstruction, retention and distension provide continuing stimulation; merely seeing food return does not imply excessive gastric contractile strength. Peritonitis and painful disease elsewhere in the abdomen can also recruit visceral afferent pathways.^[ref]

Circulating emetic agents, including some drugs and metabolic products accumulating in kidney failure, act partly through the area postrema, a chemosensitive region with unusually direct access to substances in the blood. Gastrointestinal and blood-borne inputs converge through the nucleus tractus solitarius and connected medullary networks. It is more accurate to describe interacting groups of neurons than one isolated “vomiting centre”.^[ref]

Other important groups are motion sickness, where information from the vestibular system conflicts with other sensory information; migraine and intracranial disease, including raised intracranial pressure from a brain tumour or intracranial haemorrhage; and higher-centre influences such as a repulsive sight, smell, fear or learned association. Pregnancy-associated vomiting belongs in the differential, with endocrine and central contributions rather than an explanation that it is simply mechanical pressure by the uterus upon the stomach. These causes engage different inputs to an overlapping final motor programme.^[ref]

The act itself requires several coordinated changes. The proximal stomach and lower oesophageal sphincter relax; retrograde activity can bring contents of the upper intestine into the stomach; the diaphragm and abdominal muscles generate a pressure gradient that expels the contents. During expulsion the upper passage opens while coordinated laryngeal closure helps protect the airway. Retching and actual expulsion are related stages, and neither should be confused with effortless regurgitation.^[ref]

This mechanism explains the diversity of causes: many sensory and chemical inputs can recruit the same coordinated output. A pressure recording and observation of gastrointestinal movements during an emetic response can distinguish the patterned act from a simple spontaneous return of contents; they would not, without further evidence, identify the original cause in an individual.