We have previously found high rates of poor iron and folate status in women who had delivered a low birthweight baby (LBW) in an ethnically diverse inner-city area of the UK. However, little was known of the nutritional status in the local general obstetric population. We therefore investigated biochemical measures of nutritional status in the first trimester of the first pregnancy. Routine blood samples collected at the antenatal booking clinic were analysed for haemoglobin (Hb), serum ferritin, red cell folate (RCF) (n = 100) and erythrocyte transketolase activation coefficient (ETKAC) for thiamin status (n = 90). We found 9% of women in our sample had a low Hb level, 10% had a low serum ferritin and only one had a low RCF. This is a substantially lower number of women with biochemical deficiencies than we found previously in women three months after delivering a LBW baby. However, 34% had low thiamin status. Thiamin status was negatively correlated with gestational age at birth (r = -0.407, p < 0.001). Differences in nutritional status were observed between ethnic and socio-economic groups. Hb levels differed between ethnic (p = 0.001) and socio-economic groups (p = 0.02), with Africans and women in manual occupations/unwaged having the lowest Hb levels. RCF levels also differed between groups (p < 0.001) with Caucasians and those in non-manual occupations having highest levels. ETKAC also differed between ethnic groups (p = 0.008) with Africans having the highest level indicating a poorer status. The study highlights the need to improve nutrition particularly in ethnic minorities and low income groups who are most at risk of adverse birth outcomes such as LBW.