Amniotic fluid prostaglandin F2 increases even in sterile amniotic fluid and is an independent predictor of impending delivery in preterm premature rupture of membranes

Figures & data

Table I.  Clinical characteristics and pregnancy outcomes of the study population according to the results of AF culture and MMP-8 concentrations.

	(−) AF culture low MMP-8 (Group 1; n = 81)	p*	(−) AF culture high MMP-8 (Group 2; n = 31)	p^†	(+) AF culture (Group 3; n = 2)	p^‡
Maternal age (y)	30 (21–45)	NS	31 (23–39)	NS	29 (24–37)	NS
Nulliparity (n)	40 (49%)	NS	9 (29%)	NS	9 (32%)	NS
GA at amniocentesis (week)^§	33.3 (20.4–35.0)	<0.001	29.7 (21.3–34.7)	NS	29.6 (21.6–34.3)	<0.001
GA at delivery (week)^§	34.7 (23.7–41.6)	<0.001	30.9 (22.3–35.7)	NS	30.0 (21.9–34.7)	<0.001
Amniocentesis-to-delivery interval (h)^¶	141 (0–3545)	<0.005	46 (0–1849)	NS	116 (2–748)	<0.005
AF WBC (cells/mm^3)^§	1 (0–250)	<0.001	153 (0–>1000)	NS	270 (0–>1000)	<0.001
AF MMP-8 (ng/ml)^§	1.1 (0.3–22.3)	<0.001	211.8 (35.0–2874.5)	NS	119.3 (1.6–5019.5)	<0.001

AF, amniotic fluid; MMP-8, matrix metalloproteinase-8; Low MMP-8, matrix metalloproteinase-8 <23 ng/ml; High MMP-8, matrix metalloproteinase-8 >23 ng/ml; GA, gestational age; NS, not significant; WBC, white blood cell.

Values are medians and ranges.

*Comparison between groups 1 and 2.

^†Comparison between groups 2 and 3.

^‡Comparison between groups 3 and 1.

^§P < 0.05, by Kruskal-Wallis ANOVA test.

^¶Compared by generalised Wilcoxon test for survival analysis.

Figure 1. Amniotic fluid (AF) prostaglandin F2a (PGF2a) concentrations according to the results of AF culture and AF MMP-8 concentrations (Group 1: median, 64.0 pg/ml [range, 7.7–2776.2 pg/ml]; Group 2: median, 206.2 pg/ml [range, 26.1–38715.2 pg/ml]; Group 3: median, 313.7 pg/ml [range, 40.5–8492.3 pg/ml]; p < 0.001, by Kruskal–Wallis ANOVA test).

Table II.  Clinical characteristics and pregnancy outcomes of the patients according to the concentration of AF PGF2a.

	Low PGF2a (n = 94)	High PGF2a (n = 46)	p
Maternal age (y)	30 (23–45)	30 (21–38)	NS
Nulliparity (n)	42 (45%)	16 (35%)	NS
GA at amniocentesis (week)*	32.6 (20.4–35.0)	30.5 (21.6–34.7)	NS
GA at delivery (week)*	34.3 (23.7–41.6)	31.5 (21.9–35.7)	<0.001
Amniocentesis-to-delivery interval (hour)^†	155 (0–3545)	72 (0–1849)	<0.001
within 48 h	14 (15%)	20 (44%)	<0.001
within 7 days	52 (55%)	37 (80%)	<0.005
Preterm delivery <36 weeks	80 (85%)	46 (100%)	<0.005
Positive AF culture	10 (11%)	18 (39%)	<0.001
Intra-amniotic infection/inflammation^‡	22 (23%)	37 (80%)	<0.001
AF WBC (cells/mm^3)*	1 (0–621)	397 (0–>1000)	<0.001
AF MMP-8 (ng/ml)*	1.8 (0.3–260.5)	267.0 (0.3–5019.5)	<0.001
Clinical chorioamnionitis	4 (4%)	4 (9%)	NS
Histologic chorioamnionitis (n/N)	39/72 (54%)	24/36 (67%)	NS
Funisitis (n/N)	21/74 (28%)	20/36 (56%)	<0.01

AF, amniotic fluid; MMP-8, matrix metalloproteinase-8; Low PGF2a, PGF2a <170 pg/ml; High PGF2a, PGF2a ≥170 pg/ml; GA, gestational age; NS, not significant; WBC, white blood cell.

Values are medians and ranges.

*p < 0.05, by Kruskal-Wallis ANOVA test.

^†Compared by generalised Wilcoxon test for survival analysis.

^‡Intra-amniotic infection/inflammation was defined as a positive AF culture and/or an elevated AF MMP-8 concentration (>23 ng/ml).

Table III.  AF PGF2a concentrations according to the presence or absence of intra-amniotic infection/inflammation.

	(−) Intra-amniotic infection/inflammation	(+) Intra-amniotic infection/inflammation	Total
Low PGF2a	72 (89%)	22 (37%)	94
High PGF2a	9 (11%)	37 (63%)	46
Total	81	59	140

AF, amniotic fluid; Low PGF2a, PGF2a <170 pg/ml; High PGF2a, PGF2a ≥170 pg/ml.

p < 0.001, by Chi-square test; Intra-amniotic infection/inflammation was defined as a positive AF culture and/or an elevated AF MMP-8 concentration (>23 ng/ml).

Figure 2. Survival analysis of the interval-to-delivery according to the concentration of AF PGF2a; (A) among patients without intra-amniotic infection/inflammation: median, 159 h [range, 0–3545 h]vs. median, 66 h [range, 2–141 h], p < 0.001; (B) among patients with intra-amniotic infection/inflammation: median, 137 h [range, 1–1587 h]vs. median, 75 h [range, 0–1849 h], p < 0.05.