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Summary — Bitch owners frequently wish to know whether their bitches are pregnant following a planned mating, principally out of curiosity but also so that adequate plans can be made in advance of the anticipated whelping date. Currently abdominal palpation is the preferred method for diagnosing pregnancy in bitches, the technique being most commonly carried out 3-4 weeks post-mating. In the hands of experienced veterinarians false positives are rare, but it is difficult to be certain that a bitch is not pregnant. Problems are frequently encountered in certain breeds, fat animals and in bitches which guard their abdomen. Radiography is also used on occasion in small animal practice to confirm pregnancy but it is not until d 45 that the foetal skeleton becomes visible. Foetal heartbeats can be seen using real time ultrasound from d 24-28 of pregnancy but the accuracy of the method depends to a great extent on the skill and expertise of the operator. It was against this background that workers at Cambridge Veterinary Sciences set out to develop a laboratory test to detect pregnancy in bitches. Work carried out by many authors has shown that progesterone, oestrogen and prolactin levels in the blood of pregnant bitches and in unmated bitches or those which have failed to become pregnant are very similar. Thus the detection of pregnancy by the measurement of hormone levels was precluded. However, earlier studies had shown that acute phase protein levels in the blood of pregnant bitches are significantly raised between d 28 and 37 post-mating in comparison with non-pregnant animals. A method of measuring the levels of these substances in plasma using an automated analyser was perfected, and the method tested under field conditions. The background to this study and the results obtained are reviewed. Acute phase proteins are not, of course, pregnancy-specific; they can be raised in association with stress and certain disease conditions. The significance of this is discussed.

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