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Risk Factors for Recurrence of Group B Streptococcus Colonization in a Subsequent

Pregnancy

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Shang-Yu Huang, MD, Po-Jen Cheng, MD

Linko Chang-Gung Memorial Hospital Taiwan

Introduction

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CGMH Protocol of GBS Screen

Universal screening of rectovaginal colonization of GBS in 35 ~37 weeks of gestation ＊

IAP indication:

•Previous infant with GBS

•GBS bacteriuria in current pregnancy

•Positive screening results except those for planned cesarean section without labor

•Unknown GBS status and

•Delivery < 37 weeks of gestation or

•ROM> 18 hours or

•Intrapartum fever 38≧ ℃

Not IAP indication:

•Previous positive screening result (except current positive screening )

•Planned cesarean section without labor or ROM

•Negative screening results in current pregnancy

＊ Except those with previous infant with GBS and GBS bacteriuria in current pregnancy

•Recurrence rates in a subsequent pregnancy

•Evaluating factors predictive for recurrent maternal GBS

colonization among these women.

We want to know

Materials and Methods

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Subjects

Retrospective chart review from January 2002 to December 2006

Prenatal GBS screening culture is performed between 35 and 37

weeks of gestation

Exclusion criteria:

With clinical GBS bacterial infection during the index or

subsequent pregnancy

With previous delivery of an infant with early-onset GBS disease

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Laboratory procedure

Vaginal and rectal swabs specimen collected separately

Amines transport medium (Copan ltalia, Brescia, Italy)

Non-enriched and selective LIM broth medium at 36±1 in 36 hours℃ An aliquot in plated onto 5% sheep blood agar

24 hours later, potential GBS colonies are evaluated according to morphol

ogy and the presence of hemolysis

If not GBS identified, the plate will be reincubated and inspected 48 hours

later

Mueller Hinton Agar for antimicrobial susceptibility testing (Oxoid, Unipath

Ltd, Basingstoke, UK)

Intensity of GBS

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Variables evaluation

Index pregnancy –

Maternal age, marital status, pre-pregnancy weight, weight gain

during pregnancy, infant birth weight, breast-feeding, result of

gestational diabetes mellitus (GDM) screening, intensity of GBS

colonization.

Subsequent pregnancy –

Pre-pregnancy weight, smoking, GDM screening

Time interval between the two pregnancies (months)

Ethnicity

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Statistic

SPSS 11.0 statistical package (SPSS Inc., Chicago, IL, USA)

Possible predictors was analyzed relative risks (RRs) and 95% confi

dence intervals (CIs) in univariable fashion

Potential predictors were analyzed in step-wise logistic regression

Pairwise comparison (chi-square and student’s t-test )

Two-sided P < 0.05

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Results

Table I – Univariable associations between recurrent GBS colonization and factors from the index and subsequent pregnancy.

Variable * N Recurrence of GBS: n

(%)†

RR ‡ (unadjusted)

95% CI

Maternal age: index pregnancy (years)

＜ 20 17 5 (29.4) 1.00 --

20-29 121 49 (40.5) 1.38 (0.98~1.87)

30-39 89 32 (36.0) 1.22 (0.81~1.76)

≧40 24 10 (41.7) 1.42 (0.96~1.93)

Marital status: index pregnancy

Married 222 84 (37.8) 1.00 --

Single 29 12 (41.4) 1.10 (0.79~1.63)

Ethnicity:

Taiwanese 181 67 (37.0) 1.00 --

Foreign-born 70 29 (41.4) 1.12 (0.77~1.81)

Table I – Univariable associations between recurrent GBS colonization and factors from the index and subsequent pregnancy. –cont.

Variable * N Recurrence of GBS: n

(%)†

RR ‡ (unadjusted

)

95% CI

Smoking: subsequent pregnancy

No 213 76 (35.7) 1.00 --

Yes 38 20 (52.6) 1.47 (1.03~1.83)

Pre-pregnancy weight: index pregnancy

＜ 40 kg 49 20 (40.8) 1.00 --

40-49 kg 87 32 (36.8) 0.90 (0.65~1.23)

50-59 kg 75 28 (37.3) 0.91 (0.71~1.27)

≧60 kg 40 16 (40.0) 0.98 (0.82~1.39)

Table I – Univariable associations between recurrent GBS colonization and factors from the index and subsequent pregnancy. –cont.

Variable * N Recurrence of GBS: n

(%)†

RR ‡ (unadjusted

)

95% CI

Pre-pregnancy weight: subsequent pregnancy

＜ 40 kg 35 14 (40.0) 1.00 --

40-49 kg 92 36 (39.1) 0.98 (0.77~1.42)

50-59 kg 73 27 (37.0) 0.93 (0.83~1.39)

≧60 kg 51 19 (37.3) 0.93 (0.79~1.44)

Birth weight: index pregnancy

＜ 2500 kg 21 8 (38.1) 1.00 --

2500-3999 kg 204 77 (37.7) 0.99 (0.59~1.61)

≧4000 kg 26 11 (42.3) 1.11 (0.87~1.46)

Table I – Univariable associations between recurrent GBS colonization and factors from the index and subsequent pregnancy. –cont.

Variable * N Recurrence of GBS: n

(%)†

RR ‡ (unadjusted)

95% CI

Weight gain during pregnancy: index pregnancy

＜ 5 kg 24 9 (37.5) 1.00 --

5-9 kg 118 48 (40.7) 1.09 (0.72~1.46)

10-14 kg 79 28 (35.4) 0.94 (0.65~1.28)

≧15 kg 30 11 (36.7) 0.98 (0.69~1.38)

Breast-feeding: index pregnancy

Yes 169 66 (39.1) 1.00 --

No 82 30 (36.6) 0.94 (0.58~1.60)

Table I – Univariable associations between recurrent GBS colonization and factors from the index and subsequent pregnancy. –cont.

Variable * N Recurrence of GBS: n

(%)†

RR ‡ (unadjusted)

95% CI

Time interval between index and subsequent pregnancies (months)

≧36 104 32 (30.8) 1.00 --

24-35 69 27 (39.1) 1.27 (0.79~1.68)

12-23 62 28 (45.2) 1.47 (1.01~1.99)

＜ 12 16 9 (56.3) 1.83 (1.20~2.71)

GDM screening: index pregnancy

Negative 220 80 (36.4) 1.00 --

Positive 31 16 (51.6) 1.42 (1.04~1.98)

Table I – Univariable associations between recurrent GBS colonization and factors from the index and subsequent pregnancy. –cont.

Variable * N Recurrence of GBS: n

(%)†

RR ‡ (unadjusted)

95% CI

GDM screening: subsequent pregnancy

Negative 211 75 (35.5) 1.00 --

Positive 40 21 (52.5) 1.48 (1.09~2.11)

Intensity of GBS colonization: index pregnancy

Light 52 15 (28.8) 1.00 --

Moderate 154 57 (37.0) 1.28 (0.85~1.79)

Heavy 45 24 (53.3) 1.85 (1.21~2.89)

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Summary of table I

Of the total 251 women in this study, 96 (38.2%) had GBS

colonization during the subsequent pregnancy (95% CI

33.5~42.9%)

Four potential predictors were

GDM screening result (index/subsequent pregnancy)

Intensity of GBS colonization for the index pregnancy

Smoking during subsequent pregnancy

Time interval between two pregnancies

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Table II –Predictive factors for recurrence of GBS colonization (multivariable model).

Variable Recurrence of GBS: n (%)*

Adjusted RR† (95% CI)

Time interval between index and subsequent pregnancies (months)

≧36 32 (30.8) 1.0

24-35 27 (39.1) 1.2 (0.7~1.9)

12-23 28 (45.2) 1.3 (0.9~2.1)

＜ 12 9 (56.3) 1.6 (1.1~2.4)

Intensity of GBS colonization: index pregnancy

Light 15 (28.8) 1.0

Moderate 57 (37.0) 1.2 (0.8~1.9)

Heavy 25 (53.3) 1.7 (1.2~2.6)

Discussion

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This study describes rate of recurrent GBS around 38.2%, which wa

s much higher than the incident rate of maternal colonization in our i

nstitutions (18.3%) and other local study in Chinese women (11.1%)

Besides, shorter inter-pregnancy interval and heavy GBS intensity

may be predictors for recurrent GBS colonization in a subsequent p

regnancy

Therefore, intrapartum antibiotics treatment should also be consider

ed in those pregnancies whose GBS status is unknown at the time o

f labor but with these two predictor

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The information on risk factors for recurrent GBS colonization will al

so assist health care providers in counseling women with GBS colon

ization about their risk for recurrence, the importance of appropriate

prenatal GBS screening, and intrapartum antibiotics treatment for un

known GBS status in any subsequent pregnancy.

Thanks for your attention