1. Section of Infectious Diseases, Faculty of Medicine; Imperial College London; London UK
2. Antenatal Clinic, St Mary's Hospital; Imperial College Healthcare NHS Trust; London UK
3. Department of Clinical Chemistry; Birmingham Women's Hospital; Birmingham UK
4. Department of Sexual Health, Harrison Wing; St Thomas’ Hospital; London UK
5. MRC Centre of Epidemiology for Child Health, Institute of Child Health; University College London; London UK