Table 1. Summary of current knowledge of factors affecting mother-to-child HIV-1 transmission.
Known risk factors Factors for which evidence is
suggestive but not conclusive
Factors for which evidence is
inconsistent or limited
High maternal viral load
Advanced maternal HIV disease
Low CD4 count or percent
Vaginal delivery
Duration of membrane rupture > 4 hours
Premature delivery (< 37 weeks)
No receipt of antiretroviral prophylaxis
Specific to breastfeeding transmission:
Breast milk viral load
Mastitis (including subclinical)
Cracked or bleeding nipples
Breast abscess
Duration of breastfeeding
Host genetic factors
Immature immune system in infant
Viral genotype and/or phenotype
Increased viral strain diversity
Maternal neutralizing antibody
Illicit drug use during pregnancy
Frequency of unprotected sexual intercourse
Multiple sex partners during pregnancy
Maternal nutritional status
Anemia during pregnancy
Cigarette smoking
Abruptio placentae
Sexually transmitted infections (e.g., syphilis)
Use of fetal scalp electrodes
Episiotomy and vaginal tears
Primary HIV infection in mother
Prior HIV-infected sibling
Older maternal age
Alcohol use during pregnancy
History of abortions or stillbirths
Duration of labor
Low neonatal Apgar score
Low gastric acid secretion
Immaturity of neonatal gastrointestinal tract
Infant gender
Season of birth
Placental P. falciparum infestation
Maternal vitamin A deficiency
Adapted and expanded from Bulterys (53).