Overall the proportion of women having their antenatal booking appointments late (after 12 weeks +6 days gestation) was 37.5%; with 12.1% of the total booking later than 20 weeks gestation. This is slightly higher than the NHS national average in England of 32.5% of women booking later than 12 completed weeks of gestation in the 2010–11 financial year . In certain ethnic groups the proportion of women having their antenatal booking appointments late was much higher, particularly among women who identified as Somali (55.4%), non-Somali African (44.7%) or Eastern European (43.2%).
In accordance with previous studies [6–8], our analysis showed that timing of the antenatal booking appointment varied according to maternal ethnicity; however we found that the effect was modified by English language ability and place of birth. This suggests that a combination of language barriers and unfamiliarity with the maternity services, and cultural factors may play important contributing roles in women’s timing of access to antenatal care. This was explored in a concurrent qualitative study to understand the barriers to access ; for example, Somali and Bengali women were concerned that antenatal care would be over-medicalised and thus interfere with what was perceived to be a natural process, whilst Eastern European women felt that the process was not medicalised enough. Such findings are likely to have important consequences for the design of culturally-sensitive, patient-centred and appropriate interventions targeting these groups.
One of the key reasons for prompt antenatal booking is to allow for an informed choice regarding available antenatal screening options to be made. Infants born to African and Caribbean women, identified as groups at risk of late booking in our study, are at particular risk of haemoglobin disorders, such as sickle cell anaemia . African and South Asian women are known to be at increased risk of developing gestational diabetes . In areas with relatively high HIV prevalence, such as Newham , early access to antenatal care is important in order to offer women timely interventions to reduce the risk of mother to child transmission.
Other significant predictors for late antenatal booking were young maternal age, and indicators of potential social vulnerability such as living in temporary accommodation. Having four or more previous births was the strongest risk factor for late initiation of antenatal care (aOR: 2.09; 95% CI: 1.77-2.46); this may be because women with more experience of pregnancy are more confident and may not feel the need to initiate antenatal care so early in pregnancy, especially when they have other priorities such as childcare to consider.
Maternal ethnicity was based upon self-definition in our study. It therefore primarily represents a social and cultural construct, rather than having a biological or geographic basis. Self-reported ethnicity is known to be a poor proxy for genetic make-up . It is, for example, notable that a number of women who identified themselves as British (White) yet were not able to speak English nor were born in the UK; these women may have gained citizenship through marriage or via parental descent. However, the aim of this study was to look at predictors of health-seeking behaviour which are likely to be primarily determined by socio-cultural background and life experiences, relevant to self-defined ethnicity.
Our study has a number of limitations. Data were based on self-report; there is a risk of reporting bias among women who did not speak English if adequate translation services were not available. Furthermore, there was a suggestion from the qualitative study  that women who identified as Somali may purposively report their last menstrual period as later that it truly was, in attempt to avoid induction of pregnancy. We did not find any statistically significant evidence of women who identified as Somali being more likely to have their reported last menstrual period being corrected after ultrasound (data not shown); however, if this did occur then it would mean that the true difference in late booking was under-estimated in our study.
As this study used routinely collected data, we were restricted in our analyses to available variables. We did not have information available on some potentially important risk factors; for example maternal education is known to be an important predictor of utilisation of health care. Some women may have initiated aspects of maternity care, such as smoking or alcohol cessation, prior to the booking appointment, particularly if the pregnancy was planned. Parts of the booking form completed by the midwife, such as maternal place of birth and occupation, were stored in a free-text format. This has implications for data validity as the information was not always recorded with sufficient clarity and detail; for example, over 20% of women had an “unclassifiable” occupation. Furthermore, recoding the free-text fields into a usable format was resource-intensive process.
Missing data in this study were relatively low (just 3.6% of the sample had a missing value on one or more covariate). However, it should be noted that the most recent Confidential Enquiries report into maternal deaths in the UK (CMACE) observed that many of the women who died during the 2006–2008 period had insufficient information recorded during the booking appointment to define their ‘risk status’  and it is, therefore, important to be aware that a very small but important group of women who go on to develop severe complications may potentially be over-represented among those with missing data.
Our findings provide further evidence to support the CMACE findings that additional efforts need to be made to support pregnant migrant women, particularly those who speak little or no English . However, we additionally showed that certain ethnic groups are prone to late antenatal booking after English language ability and UK birthplace/non-UK birthplace were taken into account. Antenatal care may play an important role in establishing access patterns and gaining familiarity with the healthcare system in general; for those from migrant communities pregnancy may be the first time they access the healthcare in the UK.
The identification of groups at increased risk of late antenatal booking has important public health implications. Future research should focus on effective interventions to encourage these minority groups to engage with maternity services. The results of this study (as well as the wider study ) will be used to inform a package of interventions in East London aimed at improving early and consistent access to antenatal care.