In the 2009 edition of "Williams' Obstetrics," obstetrician Dr. F. Gary Cunningham explains that the effects of chicken pox on an unborn baby depend on the timing of the exposure. Fetuses exposed before 30 weeks may exhibit a cluster of birth defects known as "congenital varicella syndrome," or the pregnancy may end in fetal loss. Babies exposed shortly before delivery face an increased risk of perinatal death due to chicken pox because the neonatal immune system is unprepared to mount a defense against the infection.
Skin Defects
In a 2008 report in "Seminars in Fetal and Neonatal Medicine," Stanford obstetricians Candace K. Smith and Ann M. Arvin describe extensive scarring in a newborn with congenital varicella syndrome. While postnatal chicken pox scars often resemble a dimple or depression, congenital varicella syndrome produces scars that appear as long, deep furrows. At birth, the scars typically retain a pink or red cast due to residual infiltration by inflammatory mediators. Over time, some scars acquire normal pigmentation while others remain relatively white and unpigmented. Some infants exhibit other kinds of skin abnormalities, as in the case of a female infant described in a 2010 report in the "Indian Journal of Pediatrics" who exhibited a large red patch of inflamed skin on her forehead.
Hypoplastic Limbs
When chicken pox strikes during the first or especially the second trimester, the result may be stunted limbs. According to Cunningham, doctors use the term "hypoplastic limbs" to describe the stunted or withered extremities seen on babies affected by congenital varicella syndrome. Hypoplastic limbs may be asymmetric, where the opposite extremity is normal, or symmetric where both limbs are markedly abnormal. In the case of hypoplastic limbs, the area supplied by a single nerve root is often devastated, while surround areas supplied by unaffected nerve roots continue to develop normally. So, the affected limbs often appear markedly abnormal as well as underdeveloped.
Eye Problems
The effects of chicken pox on the eyes are similarly severe. According to Smith and Arvin, babies are often born with markedly small eyes. Pupils may exhibit asymmetry. Visual deficits results from cataracts or an inflammatory condition known as chorioretinitis. While cataracts can be corrected surgically, chorioretinitis is less amenable to medical management. Affected children often suffer some degree of vision loss despite aggressive treatment.
Brain Abnormalities
When chicken pox strikes early during fetal development, the cortex of the brain--the part that processes conscious thought--may fail to develop or it may simply stop developing. More often, however, the brain continues to develop, but chicken pox causes inflammation and scarring within the brain. Affected children often develop seizure disorders, notes Cunningham. Mental retardation and developmental delay are also common.
Death
Chicken pox can produce death during or after pregnancy. The risk for fetal death is highest, say Smith and Arvin, before 20 weeks, at which point doctors use the term "spontaneous abortion." Death later in pregnancy--called intrauterine fetal demise--occurs less often. However, the risk of death increases again towards the end of pregnancy. According to University of Alabama Medical School Professor of Pediatrics Dr. Richard J. Whitely, infants born to women who develop chicken pox five days before delivery or up to two days after face a 30-percent risk of death due to the infection. The newborn immune system is ill-equipped to face the infection without help from maternal placental antibodies, so severe disease and death is often the result, explains Whitely.
References
- "Harrison's Principles of Internal Medicine, 23rd Edition;" A.S. Fauci et al.; 2008
- "Williams Obstetrics; 23rd Edition;" F.G. Cunningham et al.; 2009
- "Seminars in Fetal and Neonatal Medicine;" Varicella in the Fetus and Newborn; C.K. Smith and A.M. Arvin; 2009
- "Indian Journal of Pediatrics;" Congenital Varicella Syndrome/Varicella Fetopathy; R. Harish et al.; January 2010
