Characteristics of the study population
A total of 20,486 sexually active women aged 15-49 were included. Table 1 presents the distribution of the study population according to their demographic and socio-economic characteristics. Though the minority of women in the sample has consistently been adolescents, the proportion of adolescent participants has increased significantly from 5.4% in 2014 to 6.3% in 2018 (p=0.04). The proportion of women with primary or vocational education dropped significantly from 56.3% in 2014 to 50.5% in 2018 (p<0.001); while that of women with no education increased slightly from 3.6% in 2014 to 4.9% in 2018 (p=0.002) and that of women who reached the secondary education or higher increased from 40.1% in 2014 to 44.6% in 2018 (p<0.001). Participation in the study among women residing in rural areas significantly rose from 61.1% in 2014 to 68.0% in 2018 (p<0.001). The large majority of women in the sample are married but over time, the proportion of unmarried significantly increased (p<0.001). The majority of women have one to three children (about 6 in every 10 women).
{Table 1 here}
Trends in use of contraceptive methods
Table 1 also shows trends in the use of contraceptive methods, demand for family planning and the proportion of the demand that is satisfied with modern methods over time. From the results demand for contraceptives have been constant over the five-year period. Demand satisfaction have been increasing over time while modern family planning use increased between 2014 and 2015 and then it did plateau. Among the current users of contraception, there has been significant increase in the proportion using long term and permanent methods (27.1% in 2014 to 42.9% in 2018 (p<0.001) while the proportion of users of short term methods has been declining. In addition, the proportion of all sexually active women using any contraceptive method significantly increased from 57.7% in 2014 to 65.0% in 2018 with a trend analysis for proportions, p=0.005. The proportion of sexually active women using modern contraceptive methods increased by 6.0% from 57.0% in 2014 (regression slope=0.103; p<0.001). About 80.8% of the sexually active women had a demand for FP in 2014, which slightly increased to 82.6% in 2015 and then there was a decrease to 79.7% in 2018. The percent of demand for FP satisfied (DFPS) with modern contraceptives rapidly increased between 2014 and 2015 (from 70.5% to 75.7%) then there was a slow rise to 79.0% in 2018, this increase was significant (regression slope=0.019; P<0.001). Total unmet need for family planning significantly decreased from 23.8% in 2014 to 16.7% in 2018 (regression slope=-0.017; P<0.001).
Trends in contraceptive method mix
Table 2 shows the trends in contraceptive method mix (method groups) by the demographic and socioeconomic characteristics of the sampled population. The methods have been broadly grouped into: a) short acting methods (injectables, contraceptive pills, condoms, diaphragms, spermicidal agents, emergency contraception and LAM); b) long acting (IUDs, hormone implants) and permanent (male and female sterilizations) methods -LAPM; and c) traditional methods (periodic abstinence, withdrawal and other folkloric methods).
The results show a dramatic decrease overtime of the share of short-acting methods (from 71.6% in 2014 to 54.0% in 2018) and an increase in the share of LAPM (27.1% in 2014 to 42.9% in 2018). Traditional method use has stayed low throughout the period, never rising above 2.1%.
By age, the increase in the share of LAPM has been larger among women age 20 – 49 (having increased from 27.4% in 2014 to 43.5 % in 2018) than among the adolescents (from 18.4% in 2014 to 24.4% in 2018). Similarly, the decrease in the share of short-acting methods between 2014 and 2018 was more pronounced among women aged 20 – 49 years (17.9%) as compared to the decrease in use of short-acting methods among adolescents (7.0%).
Though uptake of LAPM over time has been on the increase across all the categories, we observe from the results that the uptake was higher among the (economically) least advantaged women as compared to their most advantaged counterparts – by education, wealth and residence. Indeed, the share of LAPM over time was higher among women with no education (27.7%, 43.6%, 45.6%, 54.2% and 53.7% using LAPM in 2014, 2015, 2016, 2017 and 2018 respectively) as compared to their counterparts with secondary or higher education (26.2%, 30.9%, 35.6%, 32.7% and 38.3%). The share of LAPM among women from the households in the lowest wealth quintile was higher in 2017 and 2018 (41.4% and 48.2% respectively) as compared to those from the higher wealth quintile (34.4% in 2017 and 37.2% in 2018) and the highest wealth quintile (38.7% in 2017 and 41.9% in 2018) households respectively). The same pattern was also observed among women from rural areas as compared to their counterparts in urban areas. Demographically, uptake of LAPM was higher among the most advantaged women as compared to their least advantaged counterparts – by Age, marital status and parity. By age, uptake of long-acting and permanent methods over time was higher among older women as compared to adolescent women. By marital status, uptake of long-acting and permanent methods over time was higher among married women as compared to the unmarried women. By parity, uptake of long-acting and permanent methods over time was higher among women with 4 or more children as compared to women with 1 – 3 children and women with no children. With regards to short-acting methods, there has been a general decrease in share across all categories.
{Table 2 here}
Disparities in family planning use
Figure 1 and Suppl. Fig. 1 shows the trends in contraceptive use disparities by age, residence, marital status, education, household wealth levels and parity and the corresponding 95% Confidence Intervals. For all the characteristics, there are marked disparities in FP use by all the variables considered across the years (P<0.05). The largest disparity occurs by age, education and parity. For age, the largest increase in disparity occurred between 2014 and 2015, there after there was a drop in 2017 followed by an increase in 2018.
Family planning utilization among women with secondary or higher education has also been higher than among those with no education. The same occurred by wealth index where women from resource poor households utilize FP methods less than women from rich households. From the results, there appears to be a pattern of widening poor-rich inequalities (since education can be considered to be closely related to wealth). The widening gap occurred mainly from 2014 up to 2016 but narrowed somewhat in 2017 and 2018. Compared to the other indicator variables, the inequality gap by place of residence seems narrowest.
Figure 2 shows disparities in demand satisfied with modern contraceptive methods while in Suppl. Fig 2 has the corresponding 95% CI for the differences. From the results, we observe decreasing trends in disparities in demand satisfied with modern methods among the highly educated and those with no education and among women in the highest and those in the lowest wealth quintiles since 2016. The disparity in demand satisfied with modern methods between adolescents and older women sharply increased between 2014 and 2015, which was thereafter followed by slow decrease between 2015 and 2017 and an increase in 2018. Over time, the gap in demand satisfaction between married and unmarried women have remained constant whereas between rural and urban women, the gap in demand satisfaction have slightly narrowed. In addition, though there was an initial decrease of disparities in demand satisfied with modern methods by wealth between 2014 and 2015 followed by an increase (10.3%) in 2016, there has been a consistent decrease in the level of disparity between the wealthiest and poorest women between 2016 and 2018.
Disparities in contraceptive use and demand satisfaction by demographic and socioeconomic variables
Table 3 shows the results of unadjusted odds ratios (OR) and adjusted odds ratios (aOR) for year and round of data collection as well as the county from which the data were collected. From the results, we observe that the odds of contraceptives use among sexually active older women is about 1.5 times higher than among adolescents (aOR=1.48; 95% CI: 1.21, 1.81). There is no significant difference in the odds of contraceptives use among sexually active urban and rural women (aOR=1.13; 95% CI: 0.99, 1.31). Married women have significantly lower odds of contraceptives use compared to the sexually active unmarried women (aOR 0.74; 95% CI: 0.63, 0.86). Further, the results indicate that the odds of contraception use increased with increasing education (Secondary or higher education: aOR 3.78; 95% CI: 2.90, 4.92). Similarly, the odds of contraception use increase with increasing wealth index (the highest wealth quintile: aOR = 1.36; 95% CI: 1.12, 1.65). By parity, the odds of contraceptives use among women with 4 or more children is about 5.5 times higher than among women with no children (aOR=5.47; 95% CI: 4.52, 6.61). Similar results were observed with regards to use of long acting and short acting methods.
{Table 3 here}
Regarding demand satisfied with modern contraception as shown in Table 4, older women have significantly higher odds of having their demand for FP satisfied with modern contraception as compared to adolescents (aOR = 2.40; 95% CI: 1.96, 2.93). The odds of demand satisfaction with modern contraception among urban and rural women are not different (aOR = 1.14; 95% CI: 0.97, 1.34). There are significant differences in the demand for FP satisfied with modern contraception among married and unmarried women (aOR = 1.53; 95% CI: 1.32, 1.78). Demand for FP satisfied with modern contraception increases significantly with higher education, parity and wealth index [secondary or higher education: aOR 2.39 (95% CI: 1.95, 2.94); 4 or more children: aOR=3.01 (95%CI: 2.33, 3.88); Highest wealth quintile: aOR = 1.53 (95% CI: 1.24, 1.89)]. By county of residence, the odds of demand for FP satisfied with modern contraception were significantly lower for Kilifi and West Pokot as compared to Bungoma county [Kilifi: aOR = 0.64 (95% CI: 0.49, 0.83)]; West Pokot: aOR = 0.41 (95% CI: 0.28, 0.63)] while Kiambu, Nyamira and Kakamega had significantly higher odds of having their demand for FP satisfied with modern contraception as compared to Bungoma [Kiambu: aOR = 1.48 (95% CI: 1.03, 2.13)]; Nyamira: aOR = 2.13 (95% CI: 1.55, 2.94)]; Kakamega: aOR = 1.54 (95% CI: 1.10, 2.17)].
{Table 4 here}
Concentration curves and concentration indices for contraceptives use
Figures 3 and 4 show concentration indices and the curves (for the pooled data) that summarize the disparities in single index. With the sexually active women ranked by age, residence, marital status, education, wealth and parity the concentration index indicates inequality in contraceptives use and demand satisfied by modern methods in favour of the most advantaged groups i.e. Since the concentration indices by the different demographic and socio-economic characteristics have positive values, contraceptives use and demand satisfied by modern methods are shown to be concentrated among the most advantaged groups. Concentration curves and indices for each study year are shown as supplementary materials [see Additional file 1].