The present study prospectively examined social predictors of alcohol use in early and middle pregnancy and alcohol cessation between early and middle pregnancy in Japan. Prevalence of alcohol use decreased from 20.9% in early pregnancy to 6.4% in middle pregnancy. Women with higher education were more likely to consume alcohol in early pregnancy, but were more likely to cease between early and middle pregnancy. Working women were more likely to consume alcohol in early and middle pregnancy, and women who worked in early pregnancy but not middle pregnancy were more likely to cease between early and middle pregnancy. Higher age, higher income, and psychological distress were associated with alcohol use during pregnancy.
In early pregnancy, the prevalence of alcohol use was 20.9% and higher education was associated with an increased risk of alcohol use. We could not directly compare the prevalence of alcohol use in early pregnancy with corresponding data in Japan, because there is little information on alcohol use according to pregnancy stage. The 2013 national survey among the general population of Japan, who may be non-pregnant or pregnant, revealed that women who reported alcohol use comprised 79.4% in their twenties, 77.0% in their thirties, and 77.9% in their forties [24]. Previous studies in Japan showed that about half of pregnant women retrospectively reported alcohol use before they became aware of their pregnancy [8,9,19]. Taken together, it is assumed that many women in the present study had already ceased drinking when they filled out the questionnaires administered in early pregnancy. We were able to show an association between higher education and alcohol use in early pregnancy when alcohol cessation due to pregnancy awareness had already started.
There are several possible explanations for the association between higher education and alcohol use in early pregnancy. First, alcohol use may be more acceptable among women with higher education. Specifically, more years spent in education, improved labor market prospects, increased opportunities for socialization, and delayed pregnancy mean that alcohol use has easily found a place among these women [31]. Second, social networks among highly educated people may increase the risk of alcohol use. Alcohol use can follow social networking paths [32] and highly educated women tend to associate with other highly educated people [33] who are more likely to consume alcohol [34]. Third, highly educated women may have better-paid jobs involving higher degrees of responsibility and stress as well as more chances to go out drinking with male colleagues with higher limits of drinking [35]. However, the present study showed that the association between higher education and alcohol use remained after adjustment for work status and psychological distress during pregnancy.
Higher education was also associated with alcohol cessation between early and middle pregnancy, and therefore education was not associated with alcohol use in middle pregnancy. There is some evidence that highly educated women were more likely to consume alcohol before becoming aware of their pregnancy, and more likely to continue or reduce rather than cease alcohol use during pregnancy in Western countries [12,14,16–18]. Meanwhile, two studies in Japan showed that highly educated women were more likely to cease alcohol use after becoming aware of their pregnancy [9,19]. Our finding is consistent with the previous findings in Japan. In Japan, it is mandatory for women to notify the municipal office of their pregnancy as soon as it is confirmed. At the municipal office, they receive maternal and child health handbooks [21] and tickets to use for pregnant woman health checkups at public expense. They also have access to counseling services with public health nurses, mother/parent classes, and various information services [22]. Knowledge on the health risks of alcohol use for the fetus was shown to be associated with a decreased risk of alcohol use during pregnancy [9]. Psychological and educational interventions such as supportive counselling and brief educational sessions were suggested to encourage pregnant women to cease alcohol use [36]. It is possible that highly educated women are more receptive to messages offered during the above opportunities than less educated women, because education conveys factual health-related knowledge and raises cognitive skills that affect health-promoting decisions [33,37]. However, early pregnancy is the time of greatest neurological vulnerability for the fetus [2,38]. The message that alcohol can damage a fetus even during the earliest weeks of pregnancy should be spread more widely.
Working was associated with alcohol use in early and middle pregnancy, and working in early pregnancy but not middle pregnancy was associated with alcohol cessation between these periods. Work status has been examined in many studies but was only infrequently found to be predictive [7]. Our finding are inconsistent with these previous findings that were mainly obtained in Western countries. One possible explanation for the observed association between working and alcohol use is that working people, who are more likely to have higher income, can afford to purchase alcoholic beverages [35]. However, the present study showed that the association between working and alcohol use remained after adjustment for income. Another possible explanation is that working may increase the opportunity for alcohol use. In Japan, there is a relatively high tolerance of alcohol and drinking is an important event in some working environments. For example, some working people socialize with colleagues after work in drinking meetings [23,24]. Our finding that leaving work between early and middle pregnancy was associated with alcohol cessation between these periods would support this explanation. If so, it is recommended that work colleagues should take care of pregnant women when they go out to socialize with one another.
Preconception abstinence from alcohol is preferred but difficult, because a large proportion of women of reproductive age consume alcohol [24] and women do not always plan to get pregnant [39]. It is therefore recommended that pregnant women who have already consumed alcohol during pregnancy should stop to minimize further risk [4]. A national campaign in Japan, the second term of Healthy Parents and Children 21, aims to eradicate alcohol use among pregnant women [40]. However, the present study showed that pregnant women consumed alcohol after becoming aware of their pregnancy: 20.9% in early pregnancy and 6.4% in middle pregnancy. Our findings about social predictors of alcohol use and cessation during pregnancy will be helpful for designing interventions to prevent alcohol use among pregnant women.
The present study has several limitations. First, we were able to analyze approximately half of the pregnant women who agreed to participate in the TMM BirThree Cohort Study. Women who were excluded from the analysis were less educated and more likely to be non-drinkers (Supplementary Table 1), which could lead to underestimation of the association between education and alcohol use during pregnancy. Second, the study was conducted in one of the 47 prefectures in Japan, and therefore the generalizability of the present findings is limited. A national survey reported that the prevalences of alcohol use during pregnancy were 4.3% in 2013, 1.6% in 2015, 1.3% in 2016, and 1.2% in 2017, although these were retrospective reports from mothers after childbirth [40]. Finally, alcohol use was self-reported and this can be a source of uncertainty because women may be influenced by social desirability, a bias that tends to be important when questions deal with socially undesirable attitudes and behaviors. However, the superiority of self-administered questionnaires over face-to-face interviews in measuring alcohol use during pregnancy has been supported [41].