The study was carried out at the St. Theresa's Hospital in the Nkoranza district of the Brong Ahafo Region of Ghana. The St. Theresa's hospital is a general district hospital. It has a bed capacity of 80 and provides all basic medical services including adult medicine, paediatrics, surgery and obstetrics and gynaecology. The study enrolled pregnant women of all parities attending the St. Theresa's Hospital's antenatal clinic with a gestational age of 16 weeks and above between March 2003 and September 2004.