Many unmarried women marry while pregnant, but the sex of the child is an underrecognized factor that may influence the likelihood of marriage. Son preference is common in many cultures and is known to affect prenatal decisions during pregnancy [1–5]. In some cultures, women who are pregnant with girls opt for sex-selective abortion [1–5], or in extreme cases, infanticide [3]. Some cultural groups may have more pronounced son preference due to family pressure, cultural and religious traditions, family name propagation, need to protect the marriage, and socioeconomic responsibilities [1–4, 6]. Because the sex of a child can have a strong influence on the decision to pursue a pregnancy, it is possible that unmarried pregnant women who are carrying boys may be more likely to marry because these pregnancies may be perceived as more valuable.

Marital status and family composition are well-established determinants of maternal and infant health [7, 8]. Unmarried pregnant women have an elevated risk of low birth weight, preterm birth, and small-for-gestational-age at birth after controlling for ethnicity [7], as well as a higher prevalence of postpartum depression [8]. Children of unmarried or single parents are at risk of obesity, asthma, injury, and hospitalization, as well as behavioural problems and suboptimal cognitive development [9]. Marriage during pregnancy has the potential to improve maternal and child outcomes, but the factors that influence the likelihood of marriage are not understood. Gender inequity is a widely recognized determinant of health [10]. Investigating the association between ethnicity, child sex, and marriage during pregnancy is important because identifying gender inequity in Western settings may be challenging using usual indicators. Marriage during pregnancy is a potential indicator of son preference in Western countries, where gender inequity related to pregnancy is not well understood. The objective of this study was to assess the relationship between child sex and the likelihood of marriage during pregnancy in a multicultural Western setting where son preference has been documented through sex-selective abortion [11].

There were 1,334,911 women who were unmarried at the start of pregnancy, including 45,842 women with a foreign mother tongue and 80,295 women whose region of origin was outside of Canada (Table 1). Overall, only 2.8% of French and English speakers got married during pregnancy, compared with 15.9% of women with a foreign mother tongue. Similarly, only 2.6% of Canadian-born women got married during pregnancy. In contrast, between 8.7% and 30.3% of foreign-born women got married during pregnancy. Marriage during pregnancy was most frequent among women from the Middle East and North Africa (30.3%). Women with a foreign language were more likely to be ≥ 35 years and have no high school diploma compared with French and English-speaking women (Table 2).

In adjusted regression models, mother tongue and region of origin were both associated with the probability of marriage regardless of child sex (Table 1). Compared with French and English-speaking women, women with foreign mother tongues were 6.31 times more likely to marry during pregnancy (95% CI 6.16–6.48). Women from all foreign regions of origin were more likely to marry, although associations were stronger for some regions. Women who originated from the Middle East and North Africa were 12.62 times more likely to marry (95% CI 11.94–13.34) and women from South Asia were 11.47 times more likely to marry during pregnancy (95% CI 10.22–12.87), compared with Canadian-born women.

In most cultural groups, there was no clear association between child sex and the overall probability of marriage during pregnancy (Table 3). However, women from the Middle East and North Africa who were pregnant with boys were 1.13 times more likely to marry compared with women from the same region who were pregnant with girls (95% CI 1.02–1.26). Women from Eastern Europe also had a greater tendency to marry when they were pregnant with boys (HR 1.11, 95% CI 0.98–1.26).

These patterns became more pronounced when we considered the gestational age and timing of routine ultrasounds that informed parents of the child’s sex (Figure 1). After 18 weeks of gestation, women from the Middle East and North Africa who were pregnant with boys had a higher cumulative frequency of marriage than women who were pregnant with girls. At 22 weeks, the cumulative frequency of marriage was 24.6% (95% CI 22.8–26.4) for women pregnant with boys compared with 20.4% (95% CI 20.3–23.8) for women pregnant with girls. Women from Eastern Europe exhibited similar trends. No such difference was apparent among Canadian-born women.

The association between child sex and the probability of marriage strengthened somewhat over the course of the second trimester, when a greater proportion of women likely knew the child’s sex (Table 4). Women from the Middle East and North Africa who were pregnant with boys had 1.11 times the likelihood of marriage after 12 weeks (95% CI 0.95–1.29) and 1.26 times the likelihood of marriage after 18 weeks of pregnancy (95% CI 1.04–1.53), compared with women from the same region who were pregnant with girls. Child sex was not associated with marriage among women from South Asia, East Asia, West Europe and the United States, or Canada at any gestational age.

Findings were similar when we examined mother tongue (Table 5). Women with any foreign mother tongue who were pregnant with boys were 1.08 times more likely to marry after 18 weeks of gestation (95% CI 1.00–1.16), compared with women who were pregnant with girls. Women with Arabic or other neighbouring mother tongues who were pregnant with boys were 1.32 times more likely to marry after 18 weeks (95% CI 1.04–1.68), compared with women from the same region who were pregnant with girls.

Restricting the analysis to primiparous women led to similar results although confidence intervals widened. There was no evidence of a change in associations over time.

In this study of 1.3 million women who were unmarried at conception, women originating from the Middle East, North Africa, and Eastern Europe who were pregnant with boys were more likely to marry during pregnancy than women who were pregnant with girls. The associations strengthened during the second trimester, when ultrasounds can more reliably detect the sex of the child. Child sex was not associated with the likelihood of marriage in women originating from Canada, West Europe and the United States, Asia, Sub-Saharan Africa, Latin America, and the Caribbean. These findings suggest that child sex among some cultural minorities may influence the likelihood of marriage during pregnancy. Marital status is a well-known determinant of maternal and infant health, and marriage during pregnancy may be an indicator of son preference and gender inequity that merits more attention in epidemiologic research [7, 8].

Gender inequity in maternal and child health is challenging to measure in Western settings. While many studies have examined sex and gender differences in physical and mental health [10, 20], gender inequity related to pregnancy and birth outcomes receives less attention. Most indicators of gender inequity rely on gross measures such as the World Health Organization gender inequality index (GII) and gender empowerment measure (GEM) which are based on education, income, professional positions, and political participation [21]. The GEM has a reproductive health component, but only includes maternal mortality ratios and adolescent birth rates [21]. In Quebec, gender inequity is measured by lower income and employment rates, and fewer women in leadership positions compared with men [22]. These indicators are difficult to adapt to reproductive health.

Much of the literature on gender inequity during pregnancy focuses on sex selection. Several studies have shown that countries such as India, China, South Korea, Azerbaijan, and Armenia have more than the expected 105 male births for every 100 female births [3–5]. These high sex ratios have been attributed to sex-selective abortion of female fetuses. There also is evidence that sex selection is practised among immigrant populations in Western countries [1, 2, 11]. In the 1990s, women of Indo-Pakistani descent in Quebec had a considerably elevated number of male births thought to be due to sex selection [11]. In settings where son preference has been documented, studies have shown that pregnant women who are expecting girls receive less prenatal care [23], and that girls are breastfed for a shorter period than boys [5].

In this study, women from selected cultural minorities, including the Middle East, North Africa, and Eastern Europe, had a greater likelihood of marriage if they were expecting boys. While very little literature is available on this form of gender inequity, two studies from the United States assessed marital inequality without examining differences between cultural groups [24, 25]. Women who were carrying boys were more likely to marry during pregnancy than women carrying girls, but only if they had an ultrasound during pregnancy [24]. Similarly, unmarried women who gave birth to boys were more likely to marry the child’s biological father after pregnancy than women who gave birth to girls [25]. Other research suggests that men in the United States are more likely to live with their children and less likely to divorce if they have sons [24], and that having a firstborn daughter increases the probability of living without a father [26].

Son preference is known to be influenced by cultural, religious, and societal factors [1, 2]. Some religions, including Islam, Christianity, and Jainism, limit the practice of abortion [1, 2, 6]. In communities with taboos against abortion, sex ratios at birth may not be good indicators of gender inequity or son preference because sex-selective abortions may be less accessible. Son preference may instead manifest as differences in prenatal and postnatal care, probability of having additional children, or family structure [1, 2]. This tendency may explain why we found a higher likelihood of marriage among women carrying boys from the Middle East, North Africa, and Eastern Europe—regions with large Islamic and Christian communities where abortions are less practiced [6, 27]. We found no such trend among women of South or East Asian origin, including China and India where son preference and sex-selective abortion have been documented [1, 5].

A growing body of literature suggests that marriage is beneficial to maternal and child health. Relative to unmarried women, married women have 32% lower risk of low birth weight, 18% lower risk of preterm birth, and 31% lower risk of small-for-gestational age birth [7]. The benefits appear to continue through childhood [9, 24, 28, 29]. Although children whose parents are in stable cohabitation also have better outcomes than children of single parents, the benefits are not as pronounced compared with married parents [9, 24]. Marriage increases the availability of resources, mental health, relationship quality, parenting quality, paternal involvement, and family stability [9, 30]. Marriage is associated with better cognitive performance and lower risk of behavioural problems, obesity, asthma, injury, and child hospitalization [9, 24, 28, 29]. A lower likelihood of marriage among women who are carrying girls may therefore have long-term implications for the health and development of daughters [9, 24, 25]. Attention to reducing sex-based disparities in marriage has potential to improve the health of children, especially daughters.