The population census in 2020 in Indonesia showed the total population has reached 270,02 million. This figure, of course, shows that the total population in Indonesia over the last 10 years has increased by around 32.56 million people. ¹ The increasing number of Indonesians has made the government through the National Population and Family Planning Board (BKKBN) always try to reduce the total fertility rate (TFR) for women aged 15-49 years by setting the TFR to 2.1 in 2024. Various efforts have been made by government, such as increasing the coverage of modern contraceptive use, marrying at the ideal age and providing family planning socialization to the community through IEC (Information, Education, and Communication). ²

One of the BKKBN’s efforts to reduce the birth rate in Indonesia is to urge people to marry at the ideal age, 21 years for women and 25 years for men. ³ Maturation of the age of marriage is not only beneficial for the health of women’s reproductive organs, but also shortens the reproductive period of women, which begins at the age of 15 and ends on average at the age of 49 years. Their reproductive years peak at around the age of 20 and decline gradually in their 30s. Women in their 30s who are healthy and fertile have a 20 percent chance of getting pregnant. However, for women who are 40 years old, the chance of getting pregnant is only 5 percent every month. ⁴ Research conducted by Adhikari in Nepal at 2010 also explained that the age at first marriage of a woman significantly significantly effects the average number of children born in Nepal. Women who marry younger will give birth more children until the end of their reproductive age (40-49).

Meanwhile, the results of the government performance and accountability survey [GPAS/SKAP] from 2016 to 2019 show the trend of the average age at first marriage in Indonesia ranging from 20 to 21 years and the total fertility rate [TFR] from 2016 to 2019 tends to increase. There is no significant change in this figure to achieve the TFR target of 2.1 in 2024. Based on the explanation above, it is necessary to know what is the right age at first marriage for women so that they give birth to an average of 2 children and what factors affected these births over the 3 survey periods. This study also explored the age at first marriage in each island in Indonesia, which of course is also important to know because it has different characteristics.

Based on Tables 1, 2 and 3, it can be seen that when women in the category of age at first marriage [AFM] are 10-14 years old, they have 3 to 4 children on average. The results of the GPAS/SKAP from 2017 to 2019 showedwomen who are married between 10-14 years tend to experience a decrease in births, but still have an average of 3 to 4 children. The highest fertility pattern [of children ever born in ALH] by region for AFM 10-14 years occurred in Maluku Island, namely 5.17 in 2017, then increased in 2018 [5.81] and decreased in 2019 to 4.76. The lowest birth rates in AFM [10-14] years occurred in Java and Bali, namely 3.50 in 2017, experienced a slight increase to 3.52 in 2018 and decreased to 3.19 in 2019.

While women in the AFM category [15-19] years in total, the average birth rate was still at 3.52 in 2017 and continued to decline to 3.02 in 2019. Although there was a downward trend in the number of children born each year, Figure 1 still shows that the average number of children born is 3. Meanwhile, based on archipelagic areas, AFM [15-19] years in Maluku Island has the highest birth rate, namely 4.46 in 2017, experiencing a fairly high decline to 4.29 in 2018 and then rising again in 2019 to an average 4.52 children. The lowest birth rate by region at the age of [15-19] years occurred in Java and Bali, which was around 2.97 in 2017 and continued to decline to an average birth of 2.78 children in 2019.

Then, the AFM for women aged 20-24 years old continued to decline to 3.06 in 2017 and also in 2018 and 2019 to 2.66. By region, the island of Maluku is still the region with the highest birth rate, namely 3.87 in 2017. This condition decreased to an average birth rate of 3.76 and then rose again to 3.84 in 2018-2019 respectively. The lowest birth rate for women with AFM [20-24] still occurs in Java and Bali, namely 2.55 which then decreased to 2.01 in 2018. However, this condition increased again in 2019 with an average birth rate of to 2.44.

Based on the results of the analysis of the 3 year survey data period above, the birth rate with an average of 2 children based on the table above can be achieved when AFM occurs in the [25-29] year category, namely 2.30 in 2017, which continues to experience a decrease to 2.17 in 2018 and slightly increase again in 2.22. The highest birth rate by region at the time of AFM [25-29] was still outperformed by Java and Bali, namely 1.97; 2.01 from 2017-2018 and slightly increased in 2019 to 2.07. Meanwhile, the highest birth rate by region is still occupied by Maluku Island, which is 2.76 years. 2017, then experienced an increase of 3.14 in 2018 then fell back to an average of 3.03 in 2019.

The older a woman’s AFM, the lower the birth rate. This is shown by AFM in the age category 30-34 in 2017-2019, women had given birth to children under 2 children (2.05 to 1.60). The average of women who gave birth consistently decreased from period AFM of 30-34 until the end of their reproductive period AFM of 40-44 category. This indicates that the older a person gets married for the first time, the more difficult it is to have children.

Overall, the highest birth rate is on the island of Maluku with an average birth of 3.80 children in 2017, then in 2018 it increased to an average of 3.66 children then increased again to an average of 3.78 children in 2019. Meanwhile, the lowest birth rates occurred in Java and Bali, reaching an average of 2.64 children in 2017, then increasing to an average of 2.55 children in 2018 and to an average of 2.48 in 2019.

Table 4 shows a comparison of factors related to giving birth to more than two children in 2017-2019 in women of childbearing age (aged 15-49), where it can be seen that the characteristics of women who have a tendency to have more than two children, are namely: area of residence, education level, economic status, working status, preference for the ideal number of children more than two, AFM, and family planning methods used. Economic status, age at first marriage, and use of contraceptives were significant factors influencing women aged 15-49 to have more than 2 children in the 3 survey periods [2017, 2018 and 2019] even after controlling for other factors. This shows that the 3 factors need the government’s attention on women in order to control or plan the number of children they give birth to.

From 2017 to 2019, age at first marriage was the most dominant factor for women aged 15-49 to have more than two children (2017 SOR: 4.17 95% CI [1.85-17.31], (2018 SOR: 57.14 99% [4.12-793.67]), (2019 SOR 21.22 99% CI [2.28-197.45]). While in 2019, the AFM variable for the age category 10-14 which after being adjusted by other variables remained significant in influencing women having more than 2 children (AOR 27.64 99% [2.88-265.20]). For women aged 15-49, more than 2 children is the ideal number desired, namely in 2018 (AOR: 6.55 99% CI [5.97-7.19] and in 2019 (AOR 6.58 99% [6.11-7.08]).

Marriage is a complex life stage. It also has an impact on the demographics and health of both individuals and communities related to the time of delivery. ^{5 , 6} Early marriage can have a negative impact on maternal and child health, including malnutrition and increased morbidity and mortality. ⁵ Delaying the age of marriage to a certain age can have a positive impact for women as it gives them time to develop and actualize themselves, ⁷ as well as their reproductive health because if the marriage age is too young, the reproductive organs are not completely ready for childbirth and if the marriage age is too old the chance of maternal death increases. ^{5 , 8} From a demographic perspective, this delay can reduce the number of births from the years available for pregnancy, as well as increase understanding for making decisions about fertility choices including determining the number of children. ^{6 , 7} Not only does it have a positive impact on demographic issues, the study showed that regulating the maturity of the marriage age in the law can protect the rights of women and children and increase their quality of life. ⁹

Tables 1, 2 and 3 show that women aged 15-49 who were aged 10-24 at their first marriage have a longer reproductive age range, so they have relatively more children than women who married at the age of 25 and over. The delay in the age of marriage and childbirth leads to a limitation of the biological age of pregnancy. ¹⁰ Furthermore, this analysis shows that the age of 25 years in women is a good minimum age to be able to give birth to an average of less than 3 children. Research in Uganda indicates that delaying the age of marriage beyond 20 years can change the country’s sexual behavior and fertility rates. ¹¹ Muhoza (2022) concluded that the decline in fertility rates was influenced by delays in the age of marriage. ¹² Other studies suggest that delaying the age of marriage has an impact on delaying obligations in caring for and caring for children, but this factor does not stand alone in determining the number of children you have because the level of education, economic status, and the value of the child also has a large enough contribution on one’s fertility decisions. ^{10 , 13}

Regional characteristics also show a gap in fertility trends and age at first marriage. ¹⁴ Based on 2017-2019 GPAS/SKAP data, only the Java-Bali region is consistent with a minimum age of first marriage of 25 years for women if they want to have 2 children. Other regions showed varying results in two children and age at first marriage in the 25-29 and 30-34 age groups. The trend of births in Indonesia still show a positive perspective on the relatively small number of children, but there are indications of an increase in births. The report of the 2006-2014 Susenas showed as many as 86% of women aged 15-49 have two children or less because of the success of the happy and prosperous small family program GPAS. ¹⁵ The results of this study in total, Indonesian women have 2-3 children, with the lowest scores on the islands of Java and Bali and the highest on the island of Maluku. The Java-Bali region has a low average number of children because until now development and family planning programs are still focused in that area. ^{16 , 17} Other countries in Southeast Asia share similar views regarding small families, for example in Sri Lanka. The study described a fertility preference for only having two or three children, but reported increased fertility for multifactorial reasons. ¹⁸

The data in Table 4 shows that after controlling for other factors, women who have a tendency to have more than two children are namely: living in a city, have a high education level, low economy, not working, want to have more than two children, low AFM, and using contraception tools. Several studies, both in Indonesia and in other countries found that women living in rural areas are more likely to have fewer children due to economic limitations. ^{11 , 19 , 20} This reason is also consistent with the results of this study which showed that low economic status is in line with low fertility rates as well. However, the results of studies in Europe stated that fertility was lower due to the high rate of delay in pregnancy in urban areas ²¹ and also the results of studies in Nigeria which showed differences with the findings in this study, namely that living in rural areas and the age at first marriage contributed to the high number of children. ^{22 , 23}

The assumption that those with a high level of education will have a few children was not proven in this study after being controlled by other factors. ¹¹ Higher education has a positive correlation with the desire to have two or more children because it is related to “individual agency” in determining their fertility preferences, including religious norms, child values, and ideal preferences for the number of children which are also significant in this study. ¹³ Furthermore, an understanding of fertility encourages women to determine their preference for the number of children and their fertility rights. ²⁴

Working women were positively correlated with having fewer children due to the dual burden of family and work. ²⁵ On the other hand, women who do not work have difficulties in making decisions, including decisions about fertility rights, because the “power” lies in the hands of their husbands. ²⁶ The odds ratio analysis also showed that a relatively low age at first marriage is directly proportional to a high fertility rate. This finding is also supported by other studies which stated that delaying marriage can reduce fertility rates and protect reproductive rights in women. ^{6 , 7 , 10 , 13} Another interesting finding in this study is that the use of contraceptives has a negative correlation with low fertility rates. This is different from other studies which concluded that contraceptive users have relatively few children compared to those who do not use contraception. ¹¹ This study indicates that contraception is only used after having more than two children to limit the number of births, not to regulate the number of births. ²⁷

The limitation of the study is that the data analyzed is still measured using the variable average of children ever born, it has not been measured by the total birth rate (TFR) which has taken into account child mortality. This data uses the aggregate level at the province, while district/city data is needed for programs in urban districts since district/city policies are no longer centralized (decentralization).

This study has an impact on gender issues, namely Maternal and Child Health. Therefore, proper identification of AFM can provide women’s reproductive rights so that it will reduce the problem of Maternal and Child Mortality. In addition, having less than 2 children can optimize a woman’s role as a mother in caring for her children.

The median age at first marriage in Indonesia tends to increase from year to year but is still not as expected. The median age at marriage has broad implications because it provides opportunities for women to prepare for a better future. From the aspect of reproductive health, women will become healthier and feel ready to have children. In addition, the results of the analysis prove that the call for the best age for women to first get married is 25 years, not 21 years which has always been believed. The median age of 25 for first marriage gives women the opportunity to attend higher education, so that they can join the job market.