Ureaplasma urealyticum cervical colonization as a marker for pregnancy complications

International Journal of Gynecology& Obstetrics48 (1995)15-19

Article

Ureaplasma urealyticum cervical colonization as a marker for

pregnancy complications S. Horowitz* a, J. Horowitzb, M. MazorC, A. Porathd, M. Glezerman” and Immunology, Faculty of Health Sciences, Ben-Gurion University qf the Negev, Beersheva Israel 84105 bDepartment of Medicine A, Soroka Medical Center of Kupat-Holim, Beersheva. Israel ‘Department of Obstetrics and Gynecology, Soroka Medical Center of Kupat-Holim. Beersheva, Israel ‘Department of Epidemiology, Faculty of Health Sciences, Ben-Gurion University of the Negev. Beersheva. Israel 84105

“Department of Microbiology

Received31 May 1994;revision received4 August 1994;acceptedI8 August 1994 Abstract Objectives: To determine the clinical significance of cervical colonization with (Ureaplasma urealyticum (Uu) and its possible relationship to pregnancy outcome. Methods: Cervical cultures for Uu and serum antibodies to Uu were determined in four groups of pregnant women: (1) 117 women who underwent mid-trimester amniocentesis; (2) 47 women with preterm labor and intact membranes;(3) 34 women with preterm premature rupture of membranes;and (4) a control group of 315 healthy women with normal pregnancies. Statistical methods used were the chi-square and Fisher’s exact tests. Results: A significant increase in the cervical colonization rate with Uu was detected in all study groups (62%, 77% and 74%, respectively) when compared with the control group (42%). Women at mid-trimester of pregnancy with a positive cervical culture and high levels of antibodies, had a higher rate of pregnancy complications than those with a negative culture and absenceof antibodies (62 vs. 28%, respectively; P = 0.0006). Conclusion: Cervical colonization with Uu when associatedwith elevated titers of antibodies to Uu, may serveas a marker for the identification of a subpopulation of women who are at high risk for the development of pregnancy complications. Keywords:

Ureaplasma

urealyticum;

Cervix; Antibodies to Ureaplasma;

1. Introduction Ureaplasma urealyticum (Vu) is commonly isolated from various sites during pregnancy, including the cervix, amniotic fluid, decidua, chorioamnion and placenta. It has been previously implicated as a possible pathogen in several mater-

* Correspondingauthor, Tel.: +9727 40051I; Fax: +972 7 277453.

Pregnancy outcome

nal complications of pregnancy and in neonatal morbidity [l-9]. Colonization of the chorioamnion and amniotic fluid with Uu has been demonstrated in patients with chorioamnionitis, preterm labor and delivery, low birthweight (LBW) and perinatal mortality and morbidity [l-7]. In contrast, the colonization rate with Uu in the cervix, in normal as well as in abnormal pregnancies, is usually very high but no direct association between cervical colonization

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Journal of Gynecology & Obstetrics 48 (1995) IS-19

and pregnancy complications has been reported [lO,l 11. Nevertheless the colonization rates with Uu in the lower genital tract vary significantly among populations in various geographical areas. Moreover the isolation rates reported during normal pregnancies in the United States have been found to be significantly higher than those found in other countries, 70 vs. 24-44%, respectively [lo-161. Therefore it can be postulated that the conclusions reached regarding the role of Uu infection may differ significantly between various areas. The purpose of this study was to determine the clinical significance of cervical colonization with Uu and its relationship to pregnancy outcome in a population of pregnant women in southern Israel.

mature birth was defined as delivery before 37 weeksof gestation. An LBW infant was defined as delivery of a neonate with a birthweight below 2500 g and very low birth weight was defined as less than 1500 g. 2.2 Culture procedures Cervical swabs for Ureaplasma were inserted in

10B broth [ 171and transported immediately to the laboratory and cultured within l-2 h following collection. The swab itself and IO-fold serial dilutions of the 10B broth, were plated on A8 agar plates for quantitative determination of colonyforming units (CFU). CFU of all dilutions were determined after 3-4 days. Mycoplasma hominis (Mh) was cultured in a similar way in an argininecontaining medium [ 181.

2. Patients and methods 2.3 Antibody determination 2.1. Study population

A cross-sectional study was constructed according to the gestational age, labor status and membrane conditions of the study population. Four groups of pregnant women were identified for the purposes of the study. Group 1 comprised 117 women in the mid-trimester of pregnancy (gestational age ranging from 16 to 20 weeks) undergoing transabdominal amniocentesis (mean maternal age 33.4 years f 5.1). The indications for amniocentesis were: maternal age >35 years (47%), anxiety (20%), abnormal maternal serum alpha-fetoprotein (17%), past history of neural tube defects (3%) miscellaneous (13%). Group 2 consisted of 47 consecutive women who were admitted with preterm labor and intact membranes (PTL), ranging between 22 and 34 weeks of gestation (mean maternal age 29.2 years f 5.3). Group 3 consisted of 34 women who presented with preterm premature rupture of membranes (PROM) and gestational age ranging from 24 to 36 weeks (mean maternal age 27.1 years f 5.6). Group 4 was made up of 3 15 normal healthy pregnant women (mean maternal age 28.4 years f 7.8) who served as a control group. Written consent was obtained from each patient in all groups. Relevant clinical data on past and present pregnancy outcomes of the study groups were obtained from clinical charts, including recurrent abortions, preterm delivery (PTD), LBW and stillbirth. Pre-

Antibodies to Uu in the serum were measured by a specific ELISA established in our laboratory, using an antigen prepared as previously described [ 16,17,19].In this ELISA we determined IgG antibodies to Uu antigens that were not crossreactive with other non-ureaplasmal antigens. Titers above l/160 were considered positive according to a receiver-operator characteristic curve. 2.4 Statistical methods

Statistical analysis was performed using the chisquare and Fisher’s exact tests for comparison of populations. 3. Results 3.1 Colonization of the cervix with Uu

There were no differences in the demographic data of the groups studied and all groups were similar with regard to parity, gravidity and rate of unmarried women (none of the women were single). The prevalence of colonization of the cervix with Uu during pregnancy in the study groups is presented in Table 1. In the normal pregnancy group, 42% (131/315) had a positive cervical culture for Uu, similar to the rate in our nonpregnant population (44%) [19]. In contrast, the cervical colonization rate in women with midtrimester amniocentesis, PTL and preterm PROM was 62% (72/l 17) 77% (36/47) and 74% (25/34)

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of Gynecology & Obstetrics 48 (1995) 15-19

Table I Colonization of the cervix with Uu during pregnancy

Normal pregnancy Mid-trimester amniocentesis (16-20 weeks) PTL (22-34 weeks) Preterm PROM (24-36 weeks)

C+/total”

“A

131/315

42

724117 36147 25134

O.R.b (95% C.I.)

f-value

62

2.25 (1.42-3.55)

0.0002

71

4.6 (2.16-9.99) 3.9 (1.67-9.34)

0.0001 0.0004

14

“No. of positive cultures out of the total no. of patients. bRelative to normal pregnancy.

(P = 0.0002, 0.0001 and 0.0004, respectively). The rate of intraamniotic colonization with Uu in women who had positive cervical cultures, in the three study groups, was 8172(11%) 5/36 (14%) and lo/25 (40%) respectively. 3.2 Colonization of the cervix with Mh

Cervical colonization with Mh in the control group was 8.3% (26/315), similar to that of our non-pregnant population (7.6% [8/105]). In the study groups of mid-trimester, PTL and preterm PROM, the colonization rates were 8.5% (10/l 17), 19% (9/47) and 15% (5/34), respectively. While in the latter study groups all patients who had a positive culture for Mh were also colonized with Uu, in the control group only 73% (19/26) were positive for both organisms.

tive culture of the cervix for Uu than in those with a negative culture (54% [39/72] vs. 36% [16/45]), respectively). This trend was more pronounced in patients who were both culture-positive and antibody-positive (C+/Ab+) than in those who were culture-negative and antibody-negative (C-/Ab-) (62% [24/39] vs. 28% [9/32], respectively). As shown in Fig. 1, compared with C-IAbwomen, those who had a positive cervical culture had a higher rate of adverse pregnancy outcomes

3.3 Antibodies to Uu in the serum of colonized women

Antibodies to Uu were found in 39% (22/57) of colonized women in the control group, 54% (39/72) in the mid-trimester group, 53% (18/34) in the PTL group and 56% (14/25) in the preterm PROM group. No significant differences were observed in the levels of antibody to Uu between the study groups and the control group.

a. 20 IO! 0b

C-& odda

3.4 Association between colonization andpregnancy outcome

The possible association between Uu colonization and adverse pregnancy outcome (PTL, premature PROM, PTD, fetal loss, stillbirth, LBW) was analyzed only in the mid-trimester group. As shown in Fig. 1, the percentage of adverse pregnancy outcomes was higher in women with a posi-

~ aatio:

Ab1

c1.41

c+ 3.15

C+

&

Ab+

4.27

Fig. I. Percentageof adverse pregnancy outcomes in patients undergoing amniocentesisat mid-trimester of pregnancy. Negative cervical culture for Uu with no antibodies in serum (C-/Ab-); all negative cervical cultures (C-); all positive cervical cultures (C+); positive cervical cultures plushigh titers of antibody to Uu (> 1:160)(C+/Ab-). The odds ratios comparing each group to the C-IAb- group are presented. Chi-square for linear trend 11.7, P = 0.0006

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Journal of Gynecology & Obstetrics 48 (1995) 15-19

(O.R. 3.15). C+/Ab+ women were even more likely to develop adverse perinatal outcomes (O.R. 4.25). The chi-square for linear trend was 11.7

(P = 0.0006). 4. Discussion

The results of this study indicate that the cervical colonization rate with Uu in our population during pregnancy is 42%. This rate is lower than that reported from other centers in the United States(above 70% [lO,l 11)but is similar to that in other countries, where it ranges between 24 and 44% [12-16,191. When compared with the rate of Uu in the control group, a significantly higher colonization rate with Uu was found in the patients who presented with PTL or preterm PROM, as well as in the group of patients at mid-trimester undergoing amniocentesis,which can be defined as a potential higher risk group. The statistically significant differences between the rates of colonization in the control group (42%) and the study groups (62 -77%) suggest a possible association between Uu colonization and abnormal pregnancy outcome. Similarly, McDonald et al. [15] reported a colonization rate with Uu of 35”/u during midtrimester of pregnancy, and found that colonized women had a risk for PTD almost twice as high and for preterm PROM more than 3-fold that of women with negative cultures. However, no such association was shown by Carey et al. [lo]. This discrepancy can be partly explained by the difference in colonization rates between the latter study and ours in normal pregnancies. It was previously suggestedthat antibiotic treatment against mycoplasmas during pregnancy can decreasethe incidence of prematurity (reviewed in [S]). In a recent study by Eschenbach et al. [20] it was reported that antibiotic treatment (erythromycin) administered at 30 weeks of gestation to women with positive cervical cultures with Uu did not result in a reduction in the rates of preterm PROM, PTD or LBW. It is difficult to define from the latter study the importance of Uu colonization during pregnancy for several reasons. First, the use of erythromycin was found to be less effective against Uu and failed to eradicate Uu from the

lower genital tract during pregnancy [21,22]. Second, erythromycin cannot always effectively penetrate the amniotic sac and eradicate Uu from the amniotic cavity [23]. Third, the antibiotic treatment in this multicenter study [20] was initiated only at 30 weeks of gestation. This may often be too late for success,since Uu has been detected in the amniotic cavity as early as 16 weeks of gestation [8,24] and could have already exerted its deleterious effects. Fourth, erythromycin was given to all colonized women, thus diluting those subgroups at risk (i.e. patients colonized in the upper genital tract) in a large group of women who were not at risk [20]. Our data do not necessarily suggesta cause and effect relationship but merely that Uu cervical infection may be used as an additional marker or predictor for the development of adverse pregnancy outcome. Moreover, elevated levels of antibodies to Uu together with cervical colonization, may serve as better markers for the definition of a special subpopulation of pregnant women who are at higher risk for the development of pregnancy complications. These findings were demonstrated in the group of women at mid-trimester who underwent amniocentesis (Fig. 1). It was previously shown that various factors (e.g. age, smoking, race, multiple sexual partners) were associatedwith an increased risk of preterm labor and PTD [8,11]. It should be noted that the samefactors were shown to be also associatedwith increased Uu colonization [ 10,I 1,151.Thus, it is possible that the role of Uu in the development of adversepregnancy outcome is via thesefactors and these variables are contributing factors to increased rates of Uu colonization. We have also found that cervical colonization with Mh was higher in women with PTL or preterm PROM than in the control group. In the literature there are conflicting reports concerning the role of Mh in preterm PROM and PTD [15,25]. From our study, no conclusion can be reached about the association between Mh and pregnancy outcome, since all Mh-positive patients were also Uu-positive. In conclusion, the results of our study indicate that patients with Uu colonization of the cervix and elevated titers of Uu antibodies should be con-

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sidered as having additional risk factors and/or markers for complications of pregnancy. It remains to be determined whether routine screening for Uu (cervical colonization and serum antibodies) is necessaryin all pregnant women, Acknowledgment This study was supported by grant no. 2722 (SH) from the Scientific Council of the European Communities and the National Council for Research and Development, Ministry of Science, Israel. References [I]

[2]

[3]

[4]

[5]

[6]

[7]

[S]

[9]

[IO]

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