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JAMA. 1996 Feb 28;275(8):599-605.

Identification of levels of maternal HIV-1 RNA associated with risk of perinatal transmission. Effect of maternal zidovudine treatment on viral load.

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Department of Pediatrics, UCLA School of Medicine 90024, USA.



To determine if there are levels of human immunodeficiency virus type 1 (HIV-1) associated with a high or low risk of perinatal transmission and to ascertain the mechanism by which zidovudine treatment reduces perinatal transmission.


A nonrandomized prospective cohort study.


University medical center and two general hospital affiliates from May 1989 to September 1994.


Ninety-two HIV-1-seropositive women (95 pregnancies) and their 97 infants.


Forty-two mothers (43 pregnancies) received zidovudine therapy during pregnancy and/or during labor and delivery. Eleven infants received prophylactic zidovudine for the first 6 weeks after delivery.


HIV-1 infection status of the infant.


Twenty of the 97 infants were perinatally infected with HIV-1. Transmitting mothers were more likely to have plasma HIV-1 RNA levels higher than 50000 copies per milliliter at delivery than nontransmitting mothers (15 [75.0%] of 20 transmitters vs four [5.3%] of 75 nontransmitters; P < .001). None of the 63 women with less than 20000 HIV-1 RNA copies per milliliter transmitted. Twenty-two women treated with open-label oral zidovudine during gestation showed an eightfold median decrease in plasma RNA levels (median [25th and 75th percentile], 43043 [5699 and 63053] copies per milliliter before zidovudine vs 4238 [603 and 5116] HIV-1 RNA copies per milliliter at delivery; P < .001) and none transmitted. Four zidovudine-treated women with high HIV-1 levels transmitted despite the presence of zidovudine-sensitive virus in vitro in both the mothers and their infants.


Maternal HIV-1 RNA levels were highly predictive of perinatal transmission risk and suggest that certain levels of virus late in gestation and/or during labor and delivery are associated with both a high risk and a low risk of transmission. Our results also suggest that zidovudine exerts a major protective effect by reducing maternal HIV-1 RNA levels prior to delivery and that further strategies are needed to prevent perinatal transmission in women with high or increasing virus levels and/or zidovudine-resistant virus.

[Indexed for MEDLINE]

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