Table 2. Associations with GBS carriage among 340 pregnant women with and without HIV infection, Malawi, 2008–2010*.

Variable	GBS carriage, no. positive for variable/no. total (%)	OR (95% CI)	Adjusted OR (95% CI)
All study participants	390/1,857 (21.0)	–	–
HIV-negative participants	313/1,441 (21.7)	Reference	Reference
HIV-positive participants	77/397 (19.4)	0.88 (0.66–1.17)	0.84 (0.63–1.12)
Age group, y†
16–19	68/345 (19.7)	2.29 (0.68–7.76)	1.41 (0.40–4.92)
20–24	122/582 (21.0)	2.48 (0.74–8.28)	1.96 (0.58–6.63)
25–29	113/498 (22.7)	2.74 (0.82–9.18)	2.43 (0.72–8.18)
30–34	60/261 (23.0)	2.79 (0.82–9.48)	2.59 (0.76–8.88)
35–39	24/122 (19.7)	2.29 (0.64–8.15)	2.03 (0.56–7.33)
>40	3/31 (9.7)	Reference	Reference
First pregnancy	137 (24.0)	1.30 (1.01–1.65)	1.62 (1.19–2.19)
Second or subsequent pregnancy	244 (19.6)	Reference	Reference
Recruited during rainy season	235 (22.4)	1.18 (0.94–1.50)	–
Recruited during nonrainy season	155 (19.6)	Reference	–
Birth weight <2.5 kg
No	307 (21.5)	Reference	–
Yes	71 (19.4)	0.88 (0.65–1.17)	–
Multiple birth
No	381 (21.3)	Reference	–
Yes	9 (18.0)	0.81 (0.34–1.71)	–
HIV-positive subgroup‡
Antiretroviral treatment
No	67 (20.4)	Reference	Reference
Yes	15 (18.1)	0.91 (0.45–1.75)	1.14 (0.58–2.26)§
CD4 cell count/mm3¶
<200	9 (14.1)	Reference	Reference
200–499	34 (17.2)	1.27 (0.57–2.81)	1.30 (0.58–2.92)§
>500	33 (28.2)	2.40 (1.07–5.41)	2.55 (1.10–5.90)

*GBS, group B streptococcus; OR, odds ratio; CI, confidence interval; –, not applicable. Adjusted OR derived from logistic regression by use of backward stepwise approach. Final model retained variables with p value <0.1 along with age group and parity because of their known association with GBS carriage.
†χ² test for linear trend, p = 0.93.
‡χ² test for linear trend, p = 0.01.
§Adjusted model includes age group, first pregnancy vs. second or subsequent pregnancies; antiretroviral treatment, and CD4 count for the HIV-positive subgroup.
¶19 participants had no CD4 count available.