Table 2.

Morphine concentrations measured by tandem mass spectrometry

Tissue	Time (h)	Total morphine ± SE
Maternal plasma (n = 2)	1	2825.5 ± 35.0 (ng/ml)
Placenta (n = 7)	1	2704.6 ± 99.4 (ng/g)
Fetal brain (n = 7)	1	1267.2 ± 45.4 (ng/g)
Maternal plasma (n = 3)	4	521.7 ± 73.6 (ng/ml)
Placenta (n = 11)	4	415.4 ± 10.4 (ng/g)
Fetal brain (n = 11)	4	434.0 ± 11.2 (ng/g)
Maternal plasma (n = 2)	20	<2 ng/ml

Total morphine detected at 1, 4, and 20 h after maternal injection in maternal plasma. Tissue levels in placenta and fetal brain samples were measured at 1 and 4 h only.