Methods
This cross sectional study was conducted in the obstetrics and gynaecology units of North Colombo Teaching Hospital, Sri Lanka from December 2014 to January 2017. All pregnant women with normal Hb levels (≥110 g/l in <12 weeks, >105 g/l in 13-20 weeks of gestation), booked for antenatal care within <20 weeks of gestation, were the potential study subjects(5). Among them, those with haematological diseases, active infections, liver disease, chronic connective tissue disorders, malignancies, and haemoglobinopathies were excluded(4). Written informed consent was obtained from the selected subjects. Data were gathered from interviews and antenatal records. The study was approved by the Ethics Review Committee, Faculty of Medicine, University of Kelaniya, Sri Lanka.
Blood samples were collected for FBC, blood film, and serum ferritin level. Any further treatment or follow-up was in accordance with routine clinical practice. Full blood count was analysed by a five-part Beckman Coulter analyser, while serum ferritin was estimated by a two-step immune metric technique. Blood film morphology was reported by three independent observers. If a blood film showed features of the exclusion criteria listed above, the subject’s data were excluded. Existing data from a similar Sri Lankan population at the booking visit estimated the LID to be 18%(10,17).
The sample size of the cross-sectional study was 355, calculated on the basis of 4% acceptable difference at a 95% confidence interval. The preliminary statistical analysis was limited to descriptive statistics. IBM SPSS (version 16) was used for socio-demographic, FBC, and morphology data analysis. Pearson’s chi squared test was applied to determine statistical significance. The independent t-test analysed the effect of prophylactic use of haematinics. Receiver Operating Characteristic (ROC) curves were constructed to identify optimal cut off values for red cell indices (4,12). Statistically significant P value was taken as <0.05.