(conjugate diameter, true conjugate) n. the distance between the front and rear of the pelvis measured from the most prominent part of the sacrum to the back of the pubic symphysis. Since the true conjugate cannot normally be measured during life it is estimated by subtracting 1.3–1.9 cm from the diagonal conjugate, the distance between the lower edge of the symphysis and the sacrum (usually about 12.7 cm). If the true conjugate is less than about 10.2 cm, delivery of an infant through the natural passages may be difficult or impossible, and *Caesarean section may have to be performed.
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