Doke et al. BMC Public Health 2012, 12:543 http://www.biomedcentral.com/1471-2458/12/543 Information System (HMIS) data of the Health Depart- ment, Government of Maharashtra also provides such in- formation. All above sources do not provide information about tribal areas while SRS and NFHS do not provide even district data. Vulnerability of tribal people is well documented [7]. The NRHM envisages special action plan for tribal areas. We while working under NRHM, Government of Maharashtra intended to study adverse pregnancy outcomes and relative risk in tribal areas. In the state of Maharashtra, both the sex ratio and child sex ratio have declined in the decade 1991–2001, and there- fore it was felt imperative to find out recent status of sex ratio at birth. The study was conducted utilizing available funds. Methods The study was a retrospective cohort study carried out in the State of Maharashtra, which is the second most populous state in India. As per the last census carried out in 2011, the population is 112.378 million, of which 45.23% is urban and 54.77% rural. As per 2001 census 8.85% population is tribal. Tribal people are believed to be aboriginal population of India. They inhabit in clois- tered, remote areas such as hills and forests. Their liveli- hood is dependent on archaic farming and inherent naïve products like honey, Tendu leaves etc. Their culture, language and religion are distinctive. They cus- tomarily do not socialize with dissimilar urbanity and population. As a result they are economically weak and have low levels of literacy and health. In the state there are 35 districts inclusive 2 from, Mumbai Municipal Corporation. The rural including tribal population is scattered across remaining 33 districts. The 15 districts which have substantial number of tribal population (presently minimum 0.2 million in each district) are no- tified as tribal districts. Even in these districts the tribal population mainly lives in few blocks. There are 1,816 Primary Health Centers (PHCs), out of which 320 are located in tribal pockets in these 15 districts. These 320 PHCs are designated as tribal PHCs. Each PHC has about six sub centers. An Auxiliary Nurse Midwife (ANM) manages one sub center. She records all antenatal cases in a formatted register. Only pregnant women who are residents of the sub center area are seri- ally enlisted in the register and are provided services. Pregnant women who are not residents of the sub center area are provided services without numbering. The PHC wise data is entered online for HMIS on monthly basis at block level. The cohort of 1,183,312 already registered antenatal cases in the calendar year 2008 (information from HMIS) was selected as the study population. The study started from October 2009. First, all the ANMs were instructed to write all the details of the women including Page 2 of 6 the follow up to 42 days after abortion or delivery during their home visits. After completing the data collection a summary sheet was submitted to Block Medical Officer through Medical Officer of PHC. A separate link on the website of the Directorate of Health Services, Govern- ment of Maharashtra was created to enter the new data. Training of the concerned staff was undertaken in three phases for obtaining good quality data. In first phase all the Block Medical Officers and the block level data entry operators were trained at the divisional level by the investigators. Block level personnel trained supervisors from PHCs. In the third phase ANMs were trained. For each PHC sub center wise data entry was carried out at the block level. The data entry was completed by August 2010. The data was cross checked with available HMIS data. Nil reports in any outcome and more than double the expectations were returned. The concerned ANM was once again briefed about the study and resubmission was made obligatory. Pregnancy outcome was categorized as abortion, still- birth and live birth regardless of multiple pregnancies. The investigators calculated the relative risk of abortion and stillbirth. Sex ratio at birth was also calculated. The term abortion is defined as termination of preg- nancy before 28 weeks of gestation. Abortion rate is defined as number of abortions per 100 pregnancies. Stillbirth is defined as per World Health Organization standards, "delivery of a baby after 28 weeks of gestation, but which did not show any signs of life like crying, res- piration, heartbeat or any movements", for international comparison [8]. Stillbirth rate is defined as number of stillbirths per 100 pregnancies. Sex ratio is defined as number of females per 1000 males in the population. Child Sex-ratio has been defined as the number of females in age-group 0–6 years per 1000 males in the same age-group in the population. Sex ratio at birth is defined as the number of girls born alive per 1,000 boys born alive. The study was approved and ethical clearance was given by the Institutional Committee of State Health System Resource Center, Maharashtra State. Results We studied pregnancy outcomes of 1,070,154 pregnan- cies in rural area of the Maharashtra State. About 9.6% women were lost to follow up either due to va- cancy of ANMs or non-availability of the women in their houses. Table 1 shows comparison between tribal and non-tribal PHCs. The abortion rate was higher in non-tribal PHCs and stillbirth rate was higher in tribal PHCs (χ2 = 1913.11, P < 0.0001). The relative risk of