TABLE 2. Zika virus RT-PCR results from fixed placental and fetal tissue samples from completed pregnancies for which specimens* were submitted to CDC’s Infectious Diseases Pathology Branch, by pregnancy outcome — 50 U.S. states and District of Columbia (n = 627), including 449 reported to the U.S. Zika Pregnancy Registry, January–December 2016.
| All completed pregnancies from which tissue specimens were submitted (n = 627) | ||||
|---|---|---|---|---|
| Characteristic | Live births (n = 546) |
Pregnancy losses (n = 81) |
||
| Live births with tissue specimens tested, no. | Tissue RT-PCR positive,† no. (%) | Pregnancy losses with tissue specimens tested, no. | Tissue RT-PCR positive, no. (%) | |
|
Total
|
546
|
60 (11)
|
81
|
18 (22)
|
|
Maternal clinical Zika virus test results§
| ||||
| Confirmed recent Zika virus infection |
47 |
13 (28) |
19 |
11 (58) |
| Recent unspecified flavivirus infection |
363 |
38 (10) |
13 |
4 (31) |
| Maternal samples negative by Zika virus IgM, all or part of possible exposure occurred >12 weeks before serum collected¶ |
86 |
9 (10) |
18 |
2 (11) |
| No maternal clinical samples tested** |
34 |
— |
16 |
1 (6) |
| Pending/Unknown |
2 |
— |
1 |
— |
| No evidence of possible Zika virus infection |
14 |
— |
14 |
— |
|
Infant clinical Zika virus test results
††
| ||||
| Confirmed congenital Zika virus infection |
3 |
— |
NA |
NA |
| Probable congenital Zika virus infection |
46 |
9 (20) |
NA |
NA |
| Negative Zika virus testing |
358 |
39 (11) |
NA |
NA |
| No results reported |
139 |
12 (9) |
NA |
NA |
|
Trimester of infection or possible exposure
§§
| ||||
| First trimester only |
90 |
9 (10) |
41 |
12 (29) |
| Multiple trimesters, including first |
291 |
32 (11) |
24 |
4 (17) |
| Second and/or third trimester only |
149 |
18 (12) |
4 |
— |
| Periconceptional only |
11 |
1 (9) |
10 |
2 (20) |
| Unknown/Missing |
5 |
— |
2 |
— |
|
Maternal symptom status
| ||||
| Asymptomatic |
366 |
37 (10) |
56 |
7 (13) |
| Symptomatic |
176 |
23 (13) |
25 |
11 (44) |
| Unknown |
4 |
— |
— |
— |
|
Trimester of pregnancy loss
| ||||
| Pregnancy loss, first trimester |
NA |
NA |
28 |
10 (36) |
| Pregnancy loss, second trimester |
NA |
NA |
35 |
3 (9) |
| Pregnancy loss, third trimester |
NA |
NA |
17 |
5 (29) |
| Missing |
NA |
NA |
1 |
— |
|
Completed pregnancies reported to the U.S. Zika Pregnancy Registry¶¶
(n = 449) | ||||
|
Characteristic
|
Live births (n = 414)
|
Pregnancy losses (n = 35)
|
||
|
Total
|
414
|
60 (14)
|
35
|
18 (51)
|
|
Possible Zika virus–associated birth defects***
| ||||
| Birth defects reported |
30 |
16 (53) |
4 |
2 (50) |
| No birth defects reported | 384 | 44 (11) | 31 | 16 (52) |
Abbreviations: IgM = immunoglobulin M; NA = not applicable; PRNT = plaque-reduction neutralization test; RT-PCR = reverse transcription–polymerase chain reaction.
* Includes placental specimens (placenta, fetal membranes, or umbilical cord) for all 546 live births and infant autopsy specimens for six of nine neonatal deaths. For pregnancy losses (spontaneous abortions, terminations, and stillbirths), includes placental specimens (placenta, fetal membranes, or umbilical cord) for 62 and fetal specimens for 58 pregnancy losses; both fetal and placental tissues were submitted for 38 cases.
†Tissue RT-PCR positive = at least one placental or fetal tissue specimen was positive by Zika virus RT-PCR.
§ Confirmed recent Zika virus infection = positive Zika virus RT-PCR, or Zika or dengue virus IgM positive or equivocal with Zika virus plaque-reduction neutralization test (PRNT) titer ≥10 and dengue virus PRNT titer <10; Recent unspecified flavivirus infection = negative or no Zika virus RT-PCR performed, with Zika or dengue virus IgM positive, or equivocal with Zika virus and dengue virus PRNT titers ≥10; Maternal samples negative by Zika virus IgM, all or part of possible exposure occurred >12 weeks before serum collection date = negative or no Zika virus RT-PCR performed; Zika virus IgM negative with all or part of possible exposure occurring >12 weeks before serum collection date; Pending/Unknown = Test results unknown or pending; No evidence of Zika virus infection = Zika or dengue virus IgM positive or equivocal with Zika virus PRNT titer <10 regardless of dengue virus PRNT titer, or Zika IgM negative where all possible exposure occurred within 2–12 weeks of serum collection date. Applies to results of testing on maternal clinical specimens (e.g., serum, urine). Only includes results of Zika virus clinical laboratory testing conducted in the United States and U.S. territories.
¶ Includes nine live births with negative maternal Zika virus IgM and Zika and dengue virus PRNT titers ≥10.
** Includes two live births with negative maternal Zika virus RT-PCR on serum or urine where all or part of possible exposure occurred >12 weeks before specimen collection date and no Zika virus IgM testing was performed.
†† Confirmed congenital Zika virus infection = positive Zika virus RT-PCR, Zika virus IgM positive and Zika virus PRNT titer ≥10; Probable congenital Zika virus infection = Zika virus IgM-positive, no PRNT titers reported, or Zika and dengue virus PRNT titers ≥10; Negative infant Zika virus test results = neither Zika virus RT-PCR nor Zika virus IgM positive results; No infant specimen test results reported = testing could be not performed, not reported, or pending. Applies to results of testing on infant or fetal clinical specimens (e.g., serum, cord blood, urine, cerebrospinal fluid, amniotic fluid), however if infant PRNT titers not available, maternal serum PRNT titers were used. Only includes results of Zika virus clinical laboratory testing conducted in the United States and U.S. territories.
§§ Trimester of infection or possible exposure is based on symptom onset date for symptomatic pregnant women, and for asymptomatic women was based on trimester(s) of suspected vectorborne or sexual exposure. Periconceptional exposure only is defined as infection or possible exposure during the 8 weeks before conception (6 weeks before and 2 weeks after the first day of the last menstrual period).
¶¶ U.S. Zika Pregnancy Registry inclusion criteria = Pregnant women with laboratory evidence of Zika virus infection (positive or equivocal test results, regardless of whether they have had symptoms) and periconceptionally, prenatally, or perinatally exposed infants born to these women, and infants with laboratory evidence of congenital Zika virus infection (positive or equivocal test results, regardless of whether they had symptoms) and their mothers (https://www.cdc.gov/zika/reporting/registry.html).
*** Birth defects include those that met the U.S. Zika Pregnancy Registry surveillance case definition for birth defects potentially associated with Zika virus infection during pregnancy as of May 18, 2017. These birth defects include brain abnormalities and/or microcephaly, intracranial calcifications, ventriculomegaly, neural tube defects and other early brain malformations, eye abnormalities, or other consequences of central nervous system dysfunction including arthrogryposis (joint contractures), clubfoot, congenital hip dysplasia, and congenital deafness (https://www.cdc.gov/zika/geo/pregnancy-outcomes.html).