BACKGROUND
In most societies, childbearing is largely confined to women in formal marital unions, but in a subset of contemporary low-fertility Western societies, extramarital fertility has become common. However, extramarital fertility is often ignored in fertility research in contemporary low- and middle-income countries (LMICs).

OBJECTIVE
To document recent levels, trends, and differentials in extramarital fertility (both premarital and postmarital) in LMICs.

METHODS
We employ Schoumaker’s (2013) Stata program tfr2 to calculate two fertility measures from Demographic and Health Surveys in 63 countries: (1) the standard total fertility rate (TFR), which is based on all births in the three years before the survey date, and (2) the marital total fertility rate (MTFR), which is based on all births within marital unions in the three years before the survey date. The percentage of fertility that is extramarital (PEM) is estimated as 100 x (TFR–MTFR)/TFR.

RESULTS
The unweighted average PEM for the most recent surveys in the 63 DHS countries equals 11.3%, with 7.9% premarital and 3.4% postmarital. By far the highest percentage premarital is found in southern Africa (43%) and the lowest in Asia/North Africa (0.9%). Postmarital fertility is most common in sub-Saharan Africa and Latin America.

CONCLUSIONS
Childbearing outside of marriage is an important feature of contemporary reproductive regimes in sub-Saharan Africa and Latin America. By contrast, less than 2% of births are extramarital in most Asian and North African societies.



中文翻译：

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低收入和中等收入国家的婚外生育率（作者：John Bongaarts、John Casterline）

背景
在大多数社会中，生育主要局限于正式婚姻中的女性，但在当代低生育率的西方社会的一个子集中，婚外生育已经变得普遍。然而，在当代低收入和中等收入国家（LMICs）的生育研究中，婚外生育常常被忽视。

目的
记录中低收入国家婚外生育率（婚前和婚后）的最新水平、趋势和差异。

方法
我们使用 Schoumaker (2013) 的 Stata 程序 tfr2 计算来自 63 个国家的人口和健康调查的两项生育率指标：(1) 标准总生育率 (TFR)，它基于调查日期前三年的所有出生人数， (2) 婚姻总和生育率（MTFR），以调查日期前三年内婚姻关系内的所有出生人数为基础。婚外生育率 (PEM) 估计为 100 x (TFR–MTFR)/TFR。

结果
在 63 个国土安全部国家最近的调查中，未加权平均 PEM 为 11.3%，婚前为 7.9%，婚后为 3.4%。迄今为止，婚前婚前的比例最高的是南部非洲（43%），最低的是亚洲/北非（0.9%）。婚后生育率在撒哈拉以南非洲和拉丁美洲最为普遍。

结论
婚外生育是撒哈拉以南非洲和拉丁美洲当代生殖制度的一个重要特征。相比之下，在大多数亚洲和北非社会中，婚外生的比例不到 2%。