Asymptomatic maternal shedding of herpes simplex virus at the onset of labor: relationship to preterm labor.

OBJECTIVE

To determine if fetal growth restriction and prematurity are observed with subclinical shedding of herpes simplex virus (HSV) at the onset of labor.

METHODS

Within 48 hours of delivery, cultures were taken from the cervix and external genitalia of 15,923 asymptomatic pregnant women without symptoms or signs of genital HSV infection; results were positive for HSV in 57. Each of these 57 women were compared with a control group composed of the three culture-negative women delivering immediately before and the three delivering immediately after each woman shedding HSV.

RESULTS

The median birth weight for infants born to the 57 women with asymptomatic shedding was 3050 g, compared with 3360 g among the 342 women without asymptomatic shedding, a statistically significant difference (P < .002). These differences were due to very low birth weight (LBW) among the five infants of women with subclinical viral shedding secondary to recently acquired primary genital herpes; these five infants had a median gestational age of 33 weeks, compared with 37 weeks for the 14 infants of mothers with nonprimary, first-episode disease and 39 weeks for the 33 infants of women with reactivation disease, also a significant difference (P = .018).

CONCLUSIONS

Asymptomatic genital shedding of HSV at the onset of labor because of subclinical primary genital HSV infection is associated with preterm delivery. Women who acquire genital HSV-2 before pregnancy and are shedding subclinically at the onset of labor experience no increase in adverse outcome. Thus, prevention of the prematurity and LBW associated with genital herpes means that acquisition of the infection in late pregnancy must be prevented.