Fetal ear measurements in the prenatal detection of trisomy 21

Although prominent fetal nuchal folds, short long bones, echogenic bowel, and renal pelviectasis have been shown to be associated with trisomy 21, none has acceptable diagnostic efficacy. Diminished fetal ear lengths measured by ultrasound have recently been reported as yet another potential morphological marker for the prenatal detection of trisomy 21. To investigate this further, we measured ear lengths and widths of normal (n = 107) and trisomy 21 (n = 25) second-trimester formalin-preserved fetuses. The normal ear growth characteristics are described and compared with those of trisomy 21 fetuses. The normal fetal ear shape, not unlike that of the neonates, manifested a marked variation. When the ear lengths and widths were regressed against gestational age, the slopes of the regression lines for the two groups were found to be different (P < 0·001). However, despite the statistically significant difference between the ear sizes of normal and trisomy 21 fetuses, the wide range of normal variation seen at each gestational age means that the fetal ear measurements are not diagnostically helpful.     

World phosphate supply

The Bureau of Mines investigated the resources, costs, capacities, market relationships, and short- and long-run supply of phosphate rock and phosphoric acid. The 206 mines and deposits evaluated in 30 market economy countries (MECs) contain an estimated 35.1 billion tonnes of recoverable phosphate rock (demonstrated resource level). US resources are sufficient to satisfy both the domestic market and an export market for phosphate products well beyond 2000. Resource depletion at current producers, however, means new property development (with higher costs) will be required if US production levels are to be maintained. Existing worldwide capacity can satisfy expected demand through the early 1990s. Expansion at existing mines or low demand growth could mean no new property development is required before the late 1990s. Worldwide, almost $8 billion could be required for the development of new phosphate rock properties between now and 2000, given 3% annual growth in demand. Though profit may not be the principal motivation for development of government-owned operations, most properties that could develop in the 1990s would require price increases of 20–50% to break even. To earn a 15% rate of return on investment, prices must rise to nearly double the $23–271 tonne US price level of 1988. Current US phosphate rock and phosphoric acid producers appear to be competitive (on a variable cost basis) with many other suppliers in major markets. New US properties will have higher variable costs than current producers; however, they are competitive with most projected new foreign development. The US phosphoric acid industry will most likely face increased competition as more of the foreign phosphate rock producers develop the capacity to process rock into phosphoric acid and other fertilizer products.