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Cover page of the Journal of Health Sciences

 Table of Contents  
Year : 2023  |  Volume : 16  |  Issue : 1  |  Page : 142-146

Age at marriage and first birth interval: A systematic review and meta-analysis

Department of Biostatistics and Epidemiology, KLE Academy of Higher Education and Research, Belagavi, Karnataka, India

Date of Submission18-May-2022
Date of Acceptance24-Jun-2022
Date of Web Publication21-Jan-2023

Correspondence Address:
Ms. Anushri Pradip Patil
Department of Biostatistics and Epidemiology, KLE Academy of Higher Education and Research, Belagavi - 590 010, Karnataka
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/kleuhsj.kleuhsj_418_22

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BACKGROUND: Age at marriage is one of the proximate determinants of fertility. Women with early age at marriage experiences early motherhood, associated with high fertility, low education, and rural residence accompanied with poverty. In the present study, an attempt has been made to evaluate age at marriage and factors affecting it and its effect on first birth interval (FBI) using systematic review and meta-analysis.
METHODOLOGY: Inclusion criteria were availability of full- and free-text articles, published in English language, and current married age of mother being 13 years and above. PubMed and Google search was used for systematic review for the study. Meta-analysis was carried out using Microsoft Excel 2013.
RESULTS: Pooled-weighted average age at marriage was 19.96 years (with 4.26 standard error). The age at marriage in China was highest (21.56 years). Literacy and occupation of women had significant effect on age at marriage. Urbanization could not affect significantly on age at marriage. Furthermore, FBI has been modified by age at marriage.

Keywords: Age at marriage, first birth interval, meta-analysis, systematic review

How to cite this article:
Patil AP, Tyagi NK, Prasad JB. Age at marriage and first birth interval: A systematic review and meta-analysis. Indian J Health Sci Biomed Res 2023;16:142-6

How to cite this URL:
Patil AP, Tyagi NK, Prasad JB. Age at marriage and first birth interval: A systematic review and meta-analysis. Indian J Health Sci Biomed Res [serial online] 2023 [cited 2023 Mar 27];16:142-6. Available from: https://www.ijournalhs.org/text.asp?2023/16/1/142/368325

  Introduction Top

Age at first marriage is one of the proximate determinants of fertility. The women with early age at marriage experiences early motherhood, associated with high fertility, low education, and rural residence accompanied with poverty.[1],[2],[3]

In a multicentre study conducted in 40 developing countries, it was observed that lower age at marriage (14.1 years) was associated with higher nuptiality (Longer FBI). Amongst the countries studied, Poverty was an additional influencing factor in case of Bangladesh.[4] The early age at marriage in Uttar Pradesh in 1988 was associated with median first birth interval (FBI) of 36.61 months and Assam of 24.87 months. Furthermore, lower age at marriage was observed having positive association with lower income, subcaste, and rural place of residence.[5]

Age at marriage, level of women's education, and menstrual irregularities had significant effect on birth interval after marriage.[6] Among explanatory variables of age at marriage, mother's education and occupation were significant. Furthermore, age at marriage affected FBI significantly. Out of the total study subjects, 59.9% were with two children, 16% with 3, and 10.7% with 4 or above.[7]

The Prentice-Williams-Peterson gap time (PWP-GT) conditional model revealed that, age at marriage had effect on child birth (with HR=0.69, P = 0.001) at first delivery. Also tells that, as educational level increases from secondary (with HR=0.85, P = 0.359) to academic (with HR=0.74, P = 0.183), the child birth decreased, at first delivery. And for the occupational status of a women, the childbirth ratio of employed mothers was less than the unemployed mothers (with HR=0.685, P = 0.005).[8]

Study from China (1996) estimated a median age at marriage is 18 years in 1950 with corresponding median FBI of 21 months, whereas the median age at marriage in 1985 increased to 21.7 years with FBI of 12 months, indicating inverse relationship of age at marriage and FBI.[9] Similar finding was observed from Taiwan study, indicating increase in age at marriage in the years 1970–1985; from 20 to 22 years with corresponding FBI from 27 to 16 months.[10]

Study from Iran (2015) reported a mean age at marriage of 19.5 years with a FBI of 15.4 ± 0.2 months. Furthermore, FBI was also associated with level of education and occupation of women. Women, who studied just till high schools, had FBI of 13.6 months, in higher educated women group, FBI was 25 months. In employed and working women, FBI was 17.7 compared to 15.2 months in nonworking women. The ratio of unwanted pregnancies was 5:1 in unemployed women compared to a working woman.[11]

In a study from Iran (2017) the high parity progression ratio at 5 years after marriage was 0.918, exhibiting significant effect of nonworking status of women (hazard ratio [HR] = 0.68, standard error [SE] = 0.03). The similar relationship was observed with maternal age at marriage (in 18 years and above maternal age at first pregnancy; HR = 0.93 with SE = 0.10).[8]

Study from Bangladesh (2013) observed a significant association of early age at marriage (15.5 years or less) with place of residence, religion, region, wealth index, education, and occupation using multivariate logistic regression analysis.[2]

Hence, in the present systematic review study, an attempt has been made to study the variations in age at marriage by year of a study, region, along with its determinants as place of residence, education, occupation, and effect of age at marriage on FBI.

  Methodology Top

Literature search for the present study was made with verb “age at marriage and interval from marriage to first birth (FBI).” The full-free text articles with English language and current postmarried age 13 years and above in PubMed and Google Search Engine were considered for the study.[12],[13],[14],[15],[16],[17],[18],[19],[20],[21],[22],[23],[24],[25],[26],[27],[28],[29],[30],[31],[32],[33],[34],[35],[36],[37],[38],[39],[40],[41],[42],[43],[44],[45],[46],[47],[48],[49],[50] The flowchart of the research material used in the study is:

For meta-analysis, the pooled estimates of mean and standard deviation (SD) were computed as:

between variation, i.e., η2 was calculated as:

Within-study variation was calculated as:

To study publication bias, regional variations, or cultural variations, the funnel plot has been constructed using Microsoft Excel by plotting absolute Z-transformation against estimate values. Forest plot giving place and year of the study has been constructed to understand the variation by geographical regions and time of studies carried out. Appropriate statistical models have been used to study variations by explanatory variates. The effect of explanatory variates has been studied using analysis of variance. In Meta Analysis, all articles were published with Ethical Clearance. Hence, no further Ethical Clearance is necessary.

  Results Top

Funnel plot for age at marriage [Figure 1] reveals the study publication bias, regional variations, and by year of study variations in the estimates; 11 studies could meet the inclusion criteria. Two studies, one from China conducted in 2000, and one from south India carried out in 1986, had the highest and lowest age at marriage, but they were within 1.96 of SE, hence considered for the study. Out of total 11 studies, seven exhibited in the center of the funnel plot can be considered as best. The variations in the mean age at marriage were not statistically significant at P > 0.2.
Figure 1: Funnel plot for age at marriage

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Forest plot of average age at marriage [Figure 2] reveals the variation in age at marriage by year of the study, and no trend by time or place of study could be seen. The pooled mean age at marriage was 19.96 years with SD 4.27, the variations in the age at marriage were not statistically significant (P > 0.2, Wilks Lambda = 0.86).
Figure 2: Forest plot of age at marriage

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As shown in [Figure 3], age at marriage and education reveal that literacy of women had significant effect on age at marriage (P < 0.001), following third-degree polynomial, explaining 85% of variation in mean age at marriage. In literacy group, <60% age at marriage was 17.8 years ± 4.7, which increased to 20.9 ± 4.2 in education group ≥70% [Table 1]a.
Figure 3: Age at marriage and education

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Table 1: Age at marriage by literacy, occupational status, and place of residence of women

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As shown in [Figure 4], age at marriage and occupational status of women reveal that nonworking women had significant effect on age at marriage (P < 0.001), following second-degree polynomial, explaining 76% of variation in mean age at marriage. In nonworking group, <70% age at marriage was 19.1 years ± 3.9, which increased to 19.4 ± 4 in nonworking group ≥70% [Table 1]b.
Figure 4: Age at marriage and nonworking women

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As shown in [Figure 5], age at marriage and urban place of residence of women reveal that the place of residency (percent urban) had significant effect on age at marriage (P < 0.001). In urban residence group, <35% age at marriage was 19.3 years ± 4.2 age at marriage, which decreased up to 17.9 years ± 4.3 age at marriage in ≥35% urban residence [Table 1]c.
Figure 5: Age at marriage and place of residency

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As shown in [Figure 6], FBI and age at marriage reveal that the age at marriage had impact on FBI. Out of 11 studies, seven studies had the information on FBI. FBI followed second-degree polynomial, explaining 60% of variation (R2 = 0.60). Furthermore, in marriage <20 years age at marriage, FBI fluctuated between 1.8 and 2.5 years; thereafter FBI decreased to 1.67 years in ≥20 years age at marriage [Table 2].
Figure 6: First birth interval and age at marriage

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Table 2: First birth interval by age at marriage

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From [Table 2], FBI by age at marriage revealed that in <20 years age at marriage group, the mean FBI was 1.97 years (range: 1.765, 2.5) whereas, in 20 and >20 years age at marriage, the mean FBI was 1.58 years (range: 1.67, 2).

  Discussion Top

The weighted mean of age at marriage computed from 11 studies was 19.96 years, whereas the study from China, 2000 had the highest age at marriage (21.56) and lowest in south India, 1986 (15.2 years). The reasons of high age at marriage in China might be their population policy accompanied with low fertility and higher education levels, though the south Indian study is very old (1986). Literacy of women had significant effect on increasing age at marriage, as exhibited by the studies in the increasing order Malay, Chinese, and India, 2016 to China, 2000 with corresponding education levels 50.16%–84.45% accompanied with mean age at marriage of 17.55 and 21.56 years. Occupation level of women had significant effect on age at marriage, as age at marriage decreased from 19.3 years (Northwest Ethiopia, 2014) to 18.09 years (Iran, 2013), with increasing percentage of nonworking women from 65.1% to 95.5%. Furthermore, no relationship was observed between place of residency of women and age at marriage. As a consequence of age at marriage, FBI decreased with increasing age at marriage, as was evident from Northwest Ethiopia, 2014 and Rajasthan and Kerala, 2016 with 17.55 and 19.3 years age at marriage, respectively.

  Conclusion Top

FBI varied significantly with respect to Age at Marriage, Educational Level of women and Occupational status of women. Furthermore, FBI was affected by age at marriage. Hence, area-specific planning for parenthood needs to be emphasized in population policies.


In the present study, women characteristics were studied as determinants of age at marriage, whereas spouse attributes may also affect age at marriage. Paid and abstract-only articles from PubMed and Google Scholar were not considered for meta-analysis. This can potentially alter the results of the study. Further meta-analysis is needed using these paid full-text articles to draw more valid conclusions.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]

  [Table 1], [Table 2]


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