Prevalence of <i>Streptococcus</i> B in pregnant women with preterm birth and its association with adverse outcomes

Rezende, Marianna Camilo; Rodrigues, Thamirys Pereira; Freitas, Andressa Paes Medeiros de; Lopes, Karina Souza; Araujo Júnior, Edward; Peixoto, Alberto Borges

doi:10.1590/1806-9304202500000182-en

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ORIGINAL ARTICLES • Rev. Bras. Saude Mater. Infant. 25 • 2025 • https://doi.org/10.1590/1806-9304202500000182-en linkcopy

Prevalence of Streptococcus B in pregnant women with preterm birth and its association with adverse outcomes

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Objectives: the objective this study was evaluating the prevalence of maternal colonization by Group B beta-hemolytic Streptococcus (GBS) in pregnant women who delivered preterm and its relationship with adverse maternal/perinatal outcomes.

Methods: we carried out a retrospective cohort study with singleton pregnancies with or without a culture for GBS (vaginal-rectum) who delivered spontaneously <37 weeks of gestation.

Results: the study included 190 pregnant women, 53.1% (101/190) did not undergo culture for GBS and 46.8% (89/101) have done. Among the patients who had a culture, 13.5% (12/89) had positive culture for GBS and 86.5% (77/89) had a negative culture. Pregnant women without GBS culture had higher prevalence of preterm birth (74.3 vs. 59.6%, p=0.031) and lower prevalence of antibiotic prophylaxis (27.7 vs. 56.2%, p<0.001) than pregnant women with GBS culture. Higher prevalence of crystalline penicillin G use was observed in pregnant women with positive culture compared to pregnant women with negative culture for GBS (100 vs. 39%, p<0.0001). There was no significant association between pregnant women with or without a culture for GBS or positive and negative GBS cultures and adverse maternal/perinatal outcomes.

Conclusion: No significant association was found between GBS culture or not, GBS positive or negative culture, adequate or inadequate GBS prophylaxis, and the prevalence of adverse maternal/perinatal outcomes.

Key words
Group B beta-hemolytic Streptococcus; Screening; Preterm delivery; Antibiotic prophylaxis; Adverse maternal/perinatal outcomes

Characteristics	Group I (101)	Group II (89)	Cohen’s d	p
Maternal age (years)	24.0 (13-43)	26.0 (15-40)	- 0.07	0.537 ^†
Weight (Kg)	76.3 (18.6)	74.1 (8.6)	0.17	0.806 ^∂
Height (meters)	1.65 (21.0-31.0)	1.70 (22.5-32.3)	- 0.17	1.0 ^†
Body mass index (Kg/m²)	26.0 (7.1)	26.4 (3.6)	- 0.07	0.928 ^∂
Ethnicity				0.566 ^§
White	43.6 % (44/101)	38.2% (34/89)
Black	8.9% (9/101)	6.7% (6/89)
Mixed	47.5% (48/101)	55.1% (49/89)
Asian	0.0% (0/101)	0.0% (0/89)
Number of pregnancies	2.0 (1.0-7.0)	2.0 (1.1-7.0)	- 0.11	0.532 ^†
Number of deliveries				0.797 ^§
0	44.6% (45/101)	42.7% (38/89)
≥ 1	55.4 % (56/101)	57.3% (51/89)
Gestational age at time of GBS culture (weeks)		34.7 (21.0-36.9)		^*
High-risk pregnancy	38.6 % (39/101)	41.6% (37/89)		0.678 ^§
Preterm birth	74.3% (75/101)	59.6% (53/89)		0.031 ^§
PROM	73.3% (33/45)	56.8% (25/44)		0.102 ^§
Time of PROM (hours)
Antibiotic prophylaxis for GBS	27.7% (28/101)	56.2% (50/89)		<0.001 ^§
Gestational age at delivery (weeks)	35.7 (22.4-36.9)	35.9 (25.4-36.9)	0.415	0.415 ^†
Type of delivery				0.409 ^§
Vaginal	48.9% (22/45)	56.8% (25/44)
Cesarean section	51.1% (23/45)	40.9% (18/44)
Forceps	0.05 (0/45)	2.3% (1/44)
Birth weight (grams)	2,378.0 (530.0-3,500.0)	2,520.0 (570.0-3,525.0)	- 0.10	0.438 ^†
APGAR score at the 1^st min	8.0 (1.0-9.0)	8.0 (1.0-9.0)	- 0.03	0.703 ^†
APGAR score at the 5^th min	9.0 (1.0-10.0)	9.0 (1.0-10.0)	0.05	0.838 ^†

	Group I (101)	Group II (89)	OR (95%CI)	p ^§
Early-onset neonatal sepsis	5.9% (6/101)	11.2% (10/89)	2.00 (0.69-5.75)	0.190
APGAR score at the 1^st min <7	13.9% (14/101)	13.5% (12/89)	0.96 (0.42-2.21)	0.940
Neonatal ICU admission	32.7% (33/101)	31.5% (28/89)	0.94 (0.51-1.74)	0.858
Neonatal death in the first 48 hours	5.9% (6/101)	5.6% (5/89)	0.94 (0.27-3.20)	0.924
Chorioamnionitis	2.0% (2/101)	5.6% (5/89)	2.94 (0.55-15.58)	0.184
Maternal ICU admission	2.0% (2/101)	1.1% (1/89)	0.56 (0.05-6.31)	0.636

Characteristics	Negative culture for GBS (N=77)	Positive culture for GBS (N=12)	Cohen’s d	p
Maternal age (years)	27.0 (15-40)	24.0 (16-39)	0.270	0.342 ^†
Ethnicity				0.471 ^§
White	36.4% (28/77)	50.0% (6/12)
Black	7.8% (6/77)	0.0% (0/12)
Mixed	55.8% (43/77)	50.0% (6/12)
Asian	0.0% (0/77)	0.0% (0/12)
Number of pregnancies	2.0 (1-7)	2.5 (1-7)	- 0.389	0.386 ^†
Number of deliveries				0.481 ^§
0	44.2% (34/77)	33.3% (4/12)
≥ 1	55.8% (43/77)	66.7% (8/12)
Gestational age at time of GBS culture (weeks)	34.7 (21.0-36.9)	34.6 (30.7-36.6)	- 0.230	0.460 ^†
High-risk pregnancy	41.6% (32/77)	41.7% (5/12)		0.994 ^§
Antibiotic prophylaxis for GBS	53.2% (41/77)	75.0% (9/12)		0.158 ^§
Number of doses of antibiotic prophylaxis for GBS	1.0 (0-42)	2.5 (0-24)	0.0009	0.272 ^†
Antibiotic
Crystalline penicillin G	39.0% (30/77)	100% (12/12)		<0.0001 ^§
Ampicillin	5.2% (4/77)	0.0% (0/12)		>0.999 ^§
Clindamycin	7.8% (6/77)	0.0% (0/12)		>0.999 ^§
Ceftriaxone	1.3% (1/77)	0.0% (0/12)		>0.999 ^§
None	46.7% (36/77)	0.0% (0/12)		0.0013 ^§
Adequate antibiotic treatment	45.5% (35/77)	75.0% (9/12)		0.057 ^§
Preterm birth	59.7% (46/77)	58.3% (7/12)		0.926 ^§
PROM	64.9% (50/77)	66.7% (8/12)		0.907 ^§
Time of PROM (hours)	7.0 (0.0-2016)	14.0 (0.0-1344)	- 0.137	0.523 ^†
Gestational age at delivery (weeks)	35.9 (25.4-36.9)	35.9 (30.7-36.9)	- 0.124	0.832 ^†
Type of delivery				0.863 ^§
Vaginal	51.9% (40/77)	58.3% (7/12)
Cesarean section	46.8% (36/77)	41.7% (5/12)
Forceps	1.3% (1/77)	0.0% (0/12)
Birth weight (grams)	2,520 (684-1,500)	2,635 (1,500-3,525)	- 0.298	0.358 ^†
APGAR score at the 1^st min	8.0 (1-9)	8.0 (7-9)	- 0.399	0.350 ^†
APGAR score at the 5^th min	9.0 (1-10)	9.0 (8-10)	- 0.241	0.570 ^†

	Negative culture for GBS (N=77)	Positive culture for GBS (N=12)	OR (95%CI)	p ^§
Early-onset neonatal sepsis	11.7% (9/77)	8.3% (1/12)	0.68 (0.08-5.96)	0.732
APGAR score at the 1^st min <7	15.6% (12/77)	0.0% (0/12)	0.0 (0.0-infinite)	0.141
Neonatal ICU admission	33.8% (26/77)	16.7% (2/12)	0.39 (0.08-1.92)	0.235
Neonatal death in the first 48 hours	6.5% (5/77)	0.0% (0/12)	0.0 (0.0-infinite)	0.364
Chorioamnionitis	6.5% (5/77)	0.0% (0/12)	0.0 (0.0-infinite)	0.364
Maternal ICU admission	1.3% (1/77)	0.0% (0/12)	0.0 (0.0-infinite)	0.691

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