Table 2. Temporal changes in prostaglandin F₂α and prostaglandin E₂ contents in placenta and fetal membrane.

PRG	Placenta		Fetal membrane
	PGF2α	PGE2	PGF2α	PGE2
12	9.70 ± 0.63 a	9.98 ± 1.50 a	4.24 ± 0.35 a	3.37 ± 0.27 a
15	2.69 ± 0.46 b	0.50 ± 0.08 b	3.50 ± 0.73 a	0.94 ± 0.24 b
19	1.19 ± 0.25 c	0.21 ± 0.04 c	0.99 ± 0.24 b	0.20 ± 0.11 c
21	0.94 ± 0.26 c	0.41 ± 0.11 b	0.72 ± 0.14 b	0.21 ± 0.06 c
22	0.76 ± 0.28 c	0.30 ± 0.04 bc	0.62 ± 0.11 b	0.97 ± 0.54 bc

Tissues were sampled from day 12 of pregnancy (PRG12) through PRG22 and assayed for prostaglandin (PG) F₂α and PGE₂ concentrations by the respective enzyme immunoassay. Data were standardized by protein concentration (ng/mg protein) and were expressed as mean +/−SEM (n=3~6). Different alphabetical letters within the same columns mean significant difference (P<0.05, Tukey-Kramer test).