Introduction
This was a secondary data analysis of a prospective cohort of women enrolled in a
phase III microbicide trial between October 2005 and August 2008. The study aimed to
assess the pregnancy incidence rates and factors associated with pregnancy in women
using barrier method and hormonal contraception, enrolled in the trial.
Methods
A total of 2508 participants were enrolled in the trial and followed up for up to 12
months. Of these 2437 were included in the pregnancy incidence analysis and 2171
participants were included in the multivariate analysis. Data on the main exposure,
contraception, were collected by structured interview. The main outcome of interest was
pregnancy, which was measured by detection of human chorionic gonadotrophin in
urine using Quick Vue® test and confirmed by laboratory based testing. The incidence
rate of pregnancy was calculated as number of pregnancies per 100 women years of
follow up. Kaplan Meier Survival analysis was used to determine average time to first
pregnancy. Univariate and multivariate analyses were conducted using Cox regression
models to asses the factors associated with incident pregnancies. Data was analysed
using Stata® version 10.
Results
A total of 2248 women years of follow up were recorded. A total of 238 pregnancies
occurred resulting in pregnancy incidence of 11 per 100 women-years of follow up (95%
CI: 9.32 to 12.02). The incidence of pregnancy increased with time in the study; 98 per 100 women years of follow up (95% CI: 85.09 to 112.35) in the last 3 months compared
to 2 per 100 women-years of follow up (95% CI: 0.94 to 2.92) in the first 3 months of
follow up. Older age and hormonal contraception use were significantly associated with
a decreased risk of pregnancy. Women 35 years and older were 49% less likely to fall
pregnant compared to those who were younger than 25 years, adjusted hazard ratio
(AHR) 0.51(95% CI: 0.30 to 0.88, p=0.016). Women who used hormonal contraception
had a reduced risk of falling pregnant AHR 0.66(95% CI: 0.46 to 0.94, p=0.02). There
was no difference between the two types of hormonal contraception (injectable vs oral)
with respect to pregnancy risk.
Conclusion:
The incidence of pregnancy increased with time in the study. Women who used
hormonal contraception and who were older were less at risk of pregnancy. There was
no significant difference in pregnancy risk by type of hormonal contraception (i.e. oral
contraception vs injectable contraception) used.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/10845 |
| Date | 23 November 2011 |
| Creators | Walaza, Sibongile |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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