Despite a rising prevalence worldwide, there is limited data on pregnancy outcome among African women with prepregnancy or early pregnancy obesity. This was a case-control study to determine the prevalence of maternal obesity in early pregnancy and compare the subsequent pregnancy outcome between 201 women with obesity and 201 non-obese controls in a University Teaching Hospital in Nigeria. The prevalence of obesity in early pregnancy was 9.63%. Obesity was significantly associated with advanced maternal age and parity > or =1. It was also a risk factor for pregnancy induced hypertension, admissions during pregnancy, caesarean delivery and associated with 5th minute apgar score < or =3 (0.044). Obesity in early pregnancy is a risk factor for adverse pregnancy outcome among pregnant Nigerian women. This information should be utilised by physicians to improve the outcome of pregnancy and promote safe motherhood.