Related substances (GC) (Sum of peaks with a relative retention less than that of benzyl alcohol) â¤ 0.02 %: Related substances (GC) (Sum of peaks with a relative retention greater than that of benzyl alcohol) â¤ 0.20 %: Related substances (GC) (disregard limit) â¤ 0.0001 %: Benzene (GC) â¤ 0.0002 %: Chlorobenzene (GC) â¤ 0.01 %: Toluene (GC)
If you're carrying more than one baby, chances are good you'll deliver early. Twins are usually born around 36 weeks -- four weeks early. Triplets arrive at about 33 weeks, and quads often make their debut at 31 weeks.
All fraternal twins and 20 to 30 percent of identical twins have separate placentas. By 18 to 20 weeks, a technician may be able to identify the babies' sex, assuming that both are positioned such that the technician can get a good look at their genitals.