Over 30 years ago Archie Cochrane noted that antenatal care had escaped critical assessment in terms of content . There is still a paucity of research evaluating the effectiveness of antenatal interventions specifically targeting modifiable risk factors for poor maternal and/or child health outcomes [34–36]. Recent efforts to improve the evidence base for antenatal care have focused on clinical care, smoking cessation support and on assessment of recommended visit schedules [37–40]. The relationship between the content and organisation of antenatal care and subsequent maternal and child health outcomes has received scant attention . For example, scientific knowledge about the extent to which different approaches to care (e.g. model of maternity care, pregnancy outreach workers) may influence nutrition, exercise habits, oral health, smoking, drug use, choices regarding infant feeding method, maternal depression or anxiety, intimate partner violence, inter pregnancy interval, and post pregnancy use of health services is negligible.
Our findings from a large Australian population-based survey of recent mothers attest to the high prevalence of potentially modifiable risk factors such as smoking and overweight and obesity. They also highlight a concerning level of social adversity associated with stressful life events and social health issues co-occurring with pregnancy. One in six women reported three or more stressful life events or social health issues in the 12 months before the birth. These women were much more likely to perceive that they were discriminated against in health care settings, to attend later in pregnancy and to have fewer antenatal visits. Women coping with multiple life events or social health issues remain significantly more likely to have a low birthweight infant when maternal smoking, number of antenatal visits, and other covariates are taken into account. Interpretation of the relationship between timing and number of antenatal visits and infant birthweight is complex. Our data show that some groups of women are less likely to access antenatal care early, and to attend regularly during pregnancy. The same groups of women are more likely to have adverse outcomes. This does not signify causation, but it does suggest that women who most need care and support during pregnancy are more likely to not to engage with services.
Several study limitations need to be considered. First, we used a modified life events scale originally developed for use in pregnancy  that has also been used in large scale maternity surveys in the United States and Canada [16, 30, 42]. Modifications made based on piloting and consultations preceding implementation of the HMHF Survey have not been subject to psychometric testing. Nor have we sought in this paper to differentiate different types of stressors. Our primary aim was to assess the association between low birthweight and number of stressful life events and social health issues and consider potential implications for the care of women during pregnancy. Consideration of broader questions regarding the relationship between different types of stress in pregnancy and area level deprivation are beyond the scope of analyses presented in the paper.
Second, it is plausible that women having a low birthweight infant may be more inclined to recall adverse life events in pregnancy than women who have an infant of higher birthweight, although this potential source of bias may have been lessened by the time elapsed between the birth and completing the survey at around six months postpartum. Third, we were not able to validate maternal recall of infant birthweight or maternal smoking in pregnancy. Validation studies comparing mothers' accounts of infant birthweight with medical records have shown high levels of agreement for this outcome as opposed to gestation, where there are more mixed findings [43, 44]. This was the reason for reporting infant birthweight, rather than small for gestational age. We acknowledge the potential for misclassification of maternal smoking status in early and late pregnancy. However, our finding that 17.6% of study participants reported smoking in pregnancy is in accord with routinely collected data available for seven Australian states and territories in 2007 which indicate that 16.6% of women smoked in pregnancy . We used a multiple response format for seeking information about maternal smoking which has been shown to improve disclosure of maternal smoking in self-administered questionnaires . Fourth, the sample while relatively large, provided low numbers in sub-groups for some comparisons (e.g. single women, Indigenous women).
Strengths of the study include a population-based sample drawn from two out of the eight Australian states and territories. The sampled population for the survey comprised 15% of confinements in South Australia and 8% in Victoria in 2007. While it is not possible to determine causal pathways in an observational study, the findings draw attention to social circumstances in women's lives that may place them at higher risk of poor perinatal and longer term outcomes. They also draw attention to vulnerable population groups who may be at additional risk.