Beeckman et al. BMC Public Health 2010, 10:527 http://www.biomedcentral.com/1471-2458/10/527 White British women had the highest number while Pakistani women had the lowest number. The study of Hildingsson et al. [36] found no relationship with origin. In contrast with our findings, they found that more highly educated women belonged more often to the group receiving fewer antenatal visits compared with the standard schedule. LaVeist et al. [22] found a relation- ship between educational level and the number of antenatal visits which was stronger in African American women. Age was not a predisposing determinant for the number of antenatal visits in our study, which was simi- lar to the findings of LaVeist et al. [22] and Trinh et al. [23]. Other studies show different results in the number of visits with increasing age [35,36]. Further Blondel and Marshall [37] found that women who received a maxi- mum of four antenatal visits were more often single. Our study, together with studies in the US [22], Asia [23] and Sweden [36] found no association between marital status and the number of visits. Predisposing determinants have a substantial indepen- dent influence on the number of antenatal visits and highlight groups at risk of receiving fewer antenatal vis- its. Unfortunately predisposing factors are hard to mod- ify [17]. To change these determinants would require change at a societal level and the optimization of antenatal care programmes would also be needed. Spe- cial attention needs to be paid to women with lower levels of education and to certain cultural groups. Income was the single independent enabling factor associated with the number of antenatal visits. The Viet- namese study [23] was the only one that also included the effect of income as an enabling factor. It found that the highest income group had significantly more chance of having at least three visits compared with the lowest income group. Trinh et al. [23] found more enabling determinants of the number of antenatal visits, and identified the independent effect of having health insur- ance. Women who were insured were more likely to have three antenatal visits or more. This incongruence with our study may be due to differences in the effects of having health insurance in Asia compared with Eur- ope. Blondel and Marshall [37], in France found that women with fewer than four antenatal visits were more likely to be uninsured. In this study [37] the number of women without health insurance coverage was higher compared with our findings, ranging from 13.6% in French women aged 20 or older to 71.3% in foreign women; this suggests that health insurance coverage can be a proxy for income in their study and might be the underlying cause of the difference with our findings. In an optimal model explaining health care use, the enabling factors should have minimum influence on the distribution in health services use [17], as this would secure equal availability of health care services. A low Page 6 of 9 equivalent income however was associated with a lower number of antenatal visits. With regard to pregnancy-related determinants, the differences in the number of antenatal visits related to parity were in line with antenatal care guidelines. More visits are advised in primiparae [13]. Further, women who started care after week fourteen had 32% fewer antenatal visits; this seems logical as some visits are scheduled in the first trimester. Another difference in the number of visits was observed relating to medical risks. Women with medical risks during the course of the pregnancy made 12% more visits compared with those without medical risks during pregnancy. This indi- cates that the number of visits is influenced by the increased needs that arise during pregnancy. Our study however does not allow us to examine whether the aug- mentation of the quantity of care was adequate and resulted in better outcomes. The relationship between the number of antenatal visits and gestational age at delivery was as expected, the guideline [13] suggests one or two additional visits after week 37. A higher number of antenatal visits in primiparae and women with medical risks during pregnancy were also found in the studies of Hildingsson et al. [36] and Pet- rou et al. [35]. The association between initiation of antenatal care and the number of visits was confirmed by studies in the UK [35] and Asia [23]. A history of medical risks did not seem to be related to the number of antenatal visits in Brussels or Sweden [36]. However, the study in the UK found that women with a high risk status at booking had slightly more visits [35]. We should clarify that the definition of ‘history of medical risks at booking’ did not cover exactly the same ele- ments in all three studies. The study of Hildingsson [36] only considered two elements: previous miscarriage and previous stillbirth. Women with medical disorders (eg cardiac disease, renal diseases) were excluded from our study, but were considered as high risk status at booking in the study of Petrou et al. [35]. Our study demonstrated that continuity of health care provider was associated with a reduced number of antenatal visits. The study of Petrou et al. [35] reported the opposite, with increased fragmentation leading to fewer antenatal visits. This remarkable difference might be due to the use of a different index. The COC index corrects for the number of visits to each different provi- der, while the index used by Petrou et al. [35] only divides the number of carers seen by the total number of visits. The COC index will be lower when for exam- ple a woman had fifteen visits to three different provi- ders each for five times, compared with one who visited three providers ten, two and three times respectively. This distinction is not made in the index used in the UK study [35].