Effect of group B Streptococcus infection in genital tract of pregnant women in third trimester on maternal and infant outcomes

doi:10.3877/cma.j.issn.1673-5250.2021.03.017

Objective

To explore influencing factors of group B Streptococcus (GBS) in genital tract of pregnant women in third trimester and its effects on outcomes of pregnant women and infants.

Methods

From August 2016 to August 2018, a total of 1 149 pregnant women in third trimester who received prenatal examination in People′s Hospital of Suzhou High-tech Zone and detection of GBS DNA by fluorescence quantitative PCR at gestational age of 35-37 weeks were selected as research subjects. By retrospective analysis method, they were divided into study group (n=81, GBS DNA⁺ in genital tract), and control group (n=1 068, GBS DNA^- in genital tract). Measures of intrapartum antibiotic prophylaxis (IAP) was taken to subjects in study group. Clinical data of 2 groups such as age, educational background, gravidity, parity, history of abortion, mode of delivery, gestational age and body mass index (BMI) at delivery, serum vitamin D levels, rates of gestational diabetes mellitus (GDM), premature rupture of membranes, postpartum hemorrhage, and follow-up of GBS infection of neonates in study group at 4 weeks after birth were collected. Independent-samples t test, Mann-Whitney U test and chi-square test were used for statistical comparisons. Multivariate unconditional logistic regression analysis was used to analyze influencing factors of GBS infection in genital tract of pregnant women in third trimester. The procedure in this study was in line with the requirements of Helsinki Declaration of the World Medical Association revised in 2013, and has been approved by the Ethics Committee of People′s Hospital of Suzhou High-tech Zone (Approval No. 2016-001).

Results

①There were no statistically significant differences in composition ratio of primipara and multipara, history of abortion, incidence of GDM and serum vitamin D levels between two groups (P>0.05). While there were statistically significant differences in age, composition ratio of educational background and BMI at delivery between two groups (t=-2.004, P=0.045; χ²=69.972, P<0.001; t=7.054, P<0.001). ②Multivariate unconditional logistic regression analysis showed that BMI≥25 kg/m² at delivery and high school education level or below were independent risk factors for GBS infection in genital tract of pregnant women in third trimester (OR=2.901, 6.137, 95%CI: 1.782-4.722, 3.737-10.078, all P<0.001). ③The incidence of puerperium infection and neonatal pneumonia in study group were 3.7% (3/81) and 4.9% (4/81), which were significantly higher than those in control group 0.8% (9/1 068) and 1.0% (11/1 068), respectively, and both differences were statistically significant (P=0.047; χ²=6.150, P=0.013). ④Among 81 neonates of study group, positive rate of GBS at 1 week after birth was 53.1% (43/81). The incidence of early onset GBS pneumonia in neonates was 2.5% (2/81).

Conclusions

BMI≥25 kg/m² at delivery and high school education level or below are independent risk factors for GBS infection in genital tract of pregnant women in third trimester, and may lead to increased incidence of puerperium infection and neonatal pneumonia.

Key words: Pregnancy trimester, third, Streptococcus, agalactia, Risk factors, Pregnancy outcome, Antibiotic prophylaxis, Pregnant women

表1 晚孕期孕妇发生生殖道GBS感染影响因素的单因素分析

组别	例数	年龄(岁，±s)	受教育程度[例数(%)]		分娩时BMI (kg/m²，±s)	产妇类型[例数(%)]		流产史[例数(%)]	GDM [例数(%)]	维生素D含量[ng/mL， M(P₂₅～P₇₅)]
组别	例数	年龄(岁，±s)	本科及以上	高中及以下	分娩时BMI (kg/m²，±s)	初产妇	经产妇	流产史[例数(%)]	GDM [例数(%)]	维生素D含量[ng/mL， M(P₂₅～P₇₅)]
研究组	81	29.6±4.0	24(29.6)	57(70.4)	27.5±4.7	42(51.9)	39(48.1)	43(53.1)	10(12.3)	14.2(10.4～20.6)
对照组	1 068	28.6±4.2	786(73.6)	282(26.4)	24.6±3.1	548(51.3)	520(48.7)	596(55.8)	98(9.2)	15.6(11.1～22.2)
检验值		t＝-2.004	χ²＝69.972		t＝7.054	χ²＝0.009		χ²＝0.225	χ²＝0.888	Z＝-1.802
P值		0.045	<0.001		<0.001	0.925		0.635	0.346	0.072

表1 晚孕期孕妇发生生殖道GBS感染影响因素的单因素分析

组别	例数	年龄(岁，±s)	受教育程度[例数(%)]		分娩时BMI (kg/m²，±s)	产妇类型[例数(%)]		流产史[例数(%)]	GDM [例数(%)]	维生素D含量[ng/mL， M(P₂₅～P₇₅)]
组别	例数	年龄(岁，±s)	本科及以上	高中及以下	分娩时BMI (kg/m²，±s)	初产妇	经产妇	流产史[例数(%)]	GDM [例数(%)]	维生素D含量[ng/mL， M(P₂₅～P₇₅)]
研究组	81	29.6±4.0	24(29.6)	57(70.4)	27.5±4.7	42(51.9)	39(48.1)	43(53.1)	10(12.3)	14.2(10.4～20.6)
对照组	1 068	28.6±4.2	786(73.6)	282(26.4)	24.6±3.1	548(51.3)	520(48.7)	596(55.8)	98(9.2)	15.6(11.1～22.2)
检验值		t＝-2.004	χ²＝69.972		t＝7.054	χ²＝0.009		χ²＝0.225	χ²＝0.888	Z＝-1.802
P值		0.045	<0.001		<0.001	0.925		0.635	0.346	0.072

表2 晚孕期孕妇发生生殖道GBS感染影响因素的多因素非条件logistic回归分析变量的含义及其赋值情况

自变量/因变量	变量名	赋值
孕妇是否发生GBS感染	y	y＝0表示孕妇未发生GBS感染，y＝1表示孕妇发生GBS感染
产妇类型	x₁	x₁＝0表示初产妇，x₁＝1表示经产妇
孕妇流产史	x₂	x₂＝0表示孕妇无流产史，x₂＝1表示孕妇有流产史
孕妇是否发生GDM	x₃	x₃＝0表示孕妇未发生GDM，x₃＝1表示孕妇发生GDM
孕妇分娩时BMI	x₄	x₄＝0表示孕妇分娩时BMI<25 kg/m²(孕期体重正常及偏低)，x₄＝1表示孕妇分娩时BMI≥25 kg/m²(孕期超重及肥胖)
孕妇受教育程度	x₅	x₅＝0表示孕妇受教育程度为本科及以上，x₅＝1表示孕妇受教育程度为高中及以下
孕妇年龄	x₆	x₆＝0表示孕妇年龄<35岁，x₆＝1表示孕妇年龄≥35岁

表2 晚孕期孕妇发生生殖道GBS感染影响因素的多因素非条件logistic回归分析变量的含义及其赋值情况

自变量/因变量	变量名	赋值
孕妇是否发生GBS感染	y	y＝0表示孕妇未发生GBS感染，y＝1表示孕妇发生GBS感染
产妇类型	x₁	x₁＝0表示初产妇，x₁＝1表示经产妇
孕妇流产史	x₂	x₂＝0表示孕妇无流产史，x₂＝1表示孕妇有流产史
孕妇是否发生GDM	x₃	x₃＝0表示孕妇未发生GDM，x₃＝1表示孕妇发生GDM
孕妇分娩时BMI	x₄	x₄＝0表示孕妇分娩时BMI<25 kg/m²(孕期体重正常及偏低)，x₄＝1表示孕妇分娩时BMI≥25 kg/m²(孕期超重及肥胖)
孕妇受教育程度	x₅	x₅＝0表示孕妇受教育程度为本科及以上，x₅＝1表示孕妇受教育程度为高中及以下
孕妇年龄	x₆	x₆＝0表示孕妇年龄<35岁，x₆＝1表示孕妇年龄≥35岁

表3 晚孕期孕妇发生生殖道GBS感染影响因素的多因素非条件logistic回归分析

影响因素	B	SE	Wald值	P值	OR值	OR值95%CI
产妇类型	-0.053	0.246	0.047	0.829	0.948	0.585～1.536
孕妇流产史	-0.201	0.245	0.674	0.412	0.818	0.506～1.321
孕妇是否发生GDM	0.484	0.379	1.633	0.201	1.622	0.772～3.407
孕妇分娩时BMI	1.065	0.249	18.348	<0.001	2.901	1.782～4.722
孕妇受教育程度	1.814	0.253	51.400	<0.001	6.137	3.737～10.078
孕妇年龄	0.478	0.417	1.317	0.251	1.614	0.713～3.654

表3 晚孕期孕妇发生生殖道GBS感染影响因素的多因素非条件logistic回归分析

影响因素	B	SE	Wald值	P值	OR值	OR值95%CI
产妇类型	-0.053	0.246	0.047	0.829	0.948	0.585～1.536
孕妇流产史	-0.201	0.245	0.674	0.412	0.818	0.506～1.321
孕妇是否发生GDM	0.484	0.379	1.633	0.201	1.622	0.772～3.407
孕妇分娩时BMI	1.065	0.249	18.348	<0.001	2.901	1.782～4.722
孕妇受教育程度	1.814	0.253	51.400	<0.001	6.137	3.737～10.078
孕妇年龄	0.478	0.417	1.317	0.251	1.614	0.713～3.654

表4 2组孕妇及其分娩新生儿结局比较[例数(%)]

组别	例数	分娩方式		分娩孕龄		胎膜早破	产后出血
组别	例数	自然分娩	剖宫产术分娩	≥37周	<37周	胎膜早破	产后出血
研究组	81	62(76.5)	19(23.5)	78(96.3)	3(3.7)	16(19.8)	4(4.9)
对照组	1 068	762(71.3)	306(28.7)	1 045(97.8)	22(2.1)	180(16.9)	25(2.3)
χ²值		1.002		0.338		0.406	1.144
P值		0.317		0.561		0.524	0.285
组别	例数	产褥期感染	新生儿窒息	新生儿出生体重			新生儿肺炎
组别	例数	产褥期感染	新生儿窒息	正常	巨大儿	低出生体重儿	新生儿肺炎
研究组	81	3(3.7)	2(2.5)	77(95.1)	3(3.7)	1(1.2)	4(4.9)
对照组	1 068	9(0.8)	8(0.7)	1 002(93.8)	53(5.0)	13(1.2)	11(1.0)
χ²值		—	—	1.426			6.150
P值		0.047	0.153	0.450			0.013

表4 2组孕妇及其分娩新生儿结局比较[例数(%)]

组别	例数	分娩方式		分娩孕龄		胎膜早破	产后出血
组别	例数	自然分娩	剖宫产术分娩	≥37周	<37周	胎膜早破	产后出血
研究组	81	62(76.5)	19(23.5)	78(96.3)	3(3.7)	16(19.8)	4(4.9)
对照组	1 068	762(71.3)	306(28.7)	1 045(97.8)	22(2.1)	180(16.9)	25(2.3)
χ²值		1.002		0.338		0.406	1.144
P值		0.317		0.561		0.524	0.285
组别	例数	产褥期感染	新生儿窒息	新生儿出生体重			新生儿肺炎
组别	例数	产褥期感染	新生儿窒息	正常	巨大儿	低出生体重儿	新生儿肺炎
研究组	81	3(3.7)	2(2.5)	77(95.1)	3(3.7)	1(1.2)	4(4.9)
对照组	1 068	9(0.8)	8(0.7)	1 002(93.8)	53(5.0)	13(1.2)	11(1.0)
χ²值		—	—	1.426			6.150
P值		0.047	0.153	0.450			0.013

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