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Risks of CPD and infant deaths in relation to birth weight in 1.691 million primiparas, and percentage with critical C-section in 0.486 million primiparas aged 16–20 and 0.496 million aged 21–25, United States, 1990, (all with 99% confidence intervals). CPD = cephalopelvic disproportion; C-section = cesarian section.
