AIDS

• Timing of Transmission.
• 40-80% of perinatal HIV transmission occurs during or close to the intrapartum period (1). Cd4 is present on fetal-derived placental tissue, and this tissue is capable of infection by HIV. It is believed that maternal blood does not enter the intervillous space before 12 weeks of gestation, therefore placental and fetal infection in this period presumable occurs by direct contact with infected maternal cells in the decidualized endometrium.
• Cesarean section delivery has been proposed to protect the fetus from infection. It has been estimated that cesarean section reduces the risk of transmission by 51% when compared with vaginal delivery (2).
• Mode of transmission is thought to be transplacental and initiated by either:
• Cell-to-cell spread of HIV from infected maternal mononuclear cells within the intervillous space to the trophoblastic epithelium covering the placental villi, then to the villous stroma, fetal blood vessels in the placental villi and via the fetal blood stream to the fetus itself.
• Infected maternal mononuclear cells gaining direct access to the fetal circulation (3).
• Pregnant women who are vitamin A deficient are more likely to transmit HIV to their children (4).

Ultrasound

Oligohydramnios (5).
IUGR (6,7).
Premature rupture of membranes (6).
Nonimmune hydrops (6).
Intrauterine demise and stillbirths (7).
Other co-existing infections in the mother (8):
  - Syphilis, gonorrhea, chlamydia and genital herpes.
  - Toxoplasmosis, CMV and tuberculosis can co-exist.

• Overall rate of pregnancy loss = 10-15%, however this rate varies depending on the stage of gestation (9).
• Pre-embryonic stage (3-5 weeks gestation); large number of losses without clinical recognition of pregnancy (10).
• Embryonic period (6-10 weeks gestation); majority of pregnancy loss occurs during this period with morphological ± choromosomal anomalies (11)
• Pregnancy loss in the fetal period (after 10 weeks gestation) occurs in less than 3% of pregnancies (12).
• Langston et.al. (10): Of 13 spontaneously aborted pregnancies, 3 were in the embryonic period; 11 fetal losses in the 10 pregnancies spontaneously lost between 12 and 32 weeks of gestation. The overall rate of loss was 9%.

REFERENCES

1. Minkoff H, Mofenson L. The role of obstetric interventions in the prevention of pediatric human immunodeficiency virus infection. Am J Obstet Gynecol 1994;171:1167-1175.
2. The European Collaborative Study: Cesarean section and risk of vertical transmission of HIV-I infection. Lancet 1994;343:1464-1467.
3. Hunziker RD, Gambel P, Wegmann TG. Placenta as a selective barrier to cellular traffic. J Immunol 1984;133:667-671.
4. Semba R, Miotti P, Chiphangwi J et.al. Maternal vitamin A deficiency and mother-to-child transmission of HIV-I. Lancet 1994;343:1593-1597.
5. Bardeguez A, Taylor U, Apuzzio J et.al. Characteristics of pregnant women infected with human immunodeficiency virus I (abstract WB 2044). In: International AIDS meeting, Florence, Italy, 1991.
6. Minkoff H, deRegt RH, Landesman S et.al. Pneumocystis carinii pneumonia associated with acquired immunodeficiency syndrome in pregnancy: A report of three maternal deaths. Obstet Gynecol 1986;67:284-287.
7. The Wits Study Group: Characteristics of a cohort of HIV seropositive pregnant women recruited into the women and infants transmission study (Wits) (abstract WC 3256). International AIDS meeting, Florence, Italy, 1991
8. Minkoff HL, Henderson C, Mendez H et.al. Serious infections during pregnancy among women with advanced human immunodeficiency virus infection. Am J Obstet Gynecol 1990;162:30-34.
9. Branch DW. Thoughts on the mechanism of pregnancy loss associated with the antiphospholipid syndrome. Lupus 1994;3:275-278.
10. Langston C, Lewis DE, Hammill HA et.al. Excess intrauterine fetal demise associated with maternal human immunodeficiency virus infection. J Infect Dis 1995;172:1451-1460.
11. Byrne Y, Warburton D, Kline J et.al. Morphology of early fetal deaths and their chromosomal characteristics. Teratology 1985;32:297-315.
12. Simpson JL, Mills JL, Holmes LB et.al. Low fetal loss rate after ultrasound-proved viability in early pregnancy. JAMA 1987;258:2555-25557.