|Inclusion criteria||Exclusion criteria|
|Women < 40 years old||Women who conceived the fetus using artificial methods including in-vitro fertilization or intrauterine insemination|
|Aboriginal ancestry||Women carrying more than one fetus|
|Pregnant with singleton||Surrogate mothers|
|Women who suffer from severe chronic medical conditions including active cancer, severe infectious diseases including HIV, hepatitis B or C, or who are VDRL positive|
Wahi et al.
Wahi et al. BMC Public Health 2013 13:608 doi:10.1186/1471-2458-13-608