Table 1. Data extracted for the qualitative synthesis.

Article	Study site (State, country)	Study design	Study objective	Study timeframe	Population	Total cases of congenital microcephalia	Total cases of microcephalia of infectious etiology		Total cases of microcephalia of infectious etiology with laboratory or radiological confirmation (congenital infection)		Limitations	GRADE
						Absolute Nº	Absolute Nº	%	Absolute Nº	%
Oliveira et al.19	All Federation States	Descriptive population-based	Report temporal and geospatial evidence linking preceding ZIKV transmission to increased prevalence of microcephaly in Brazil	01/01/2015 to 07/01/2016 (and those reported between 19/11/2015 and 07/01/2016)	Microcephalia cases reported on SINASC between 2000 and 2014, and NBs with microcephalia identified through the surveillance system from 01/01/2015 to 07/01/2016.	574	574	100%	Not informed**	-	1) Ecological analysis, with limited laboratory evidence of ZIKV infection for the pregnancy outcome described. 2) Data obtained from the MS surveillance system after identification of the first cases possibly related to maternal ZIKV infection. Awareness of professionals regarding this event may have resulted in an overestimation of cases, including the identification of false positives. 3) Microcephaly was probably underestimated in Brazil before the ZIKV outbreak, so the increase may not be as large as suggested by these findings. 4) The analysis was limited to the temporal and geospatial association between the increased prevalence of microcephaly in Brazil and early ZIKV transmission, and other possible causes of microcephaly were not evaluated. 5) Few serological confirmations of viral infection in pregnancy occurred.	Very Low (outcome measurement bias, indirect evidence)
Magalhães-Barbosa et al. 20	All Federation States	Narrative revision	Based on data published by the MS, report the tendency of microcephaly cases and ZIKV disease.	08/11/2015 to 02/07/2016	NBs with congenital microcephaly or other CNS disorders notified to the MS	1,656*	255	15%	255 ZIKV	100%	1) At the end, 3,130 (37.7%) of 8,301 cases of microcephaly and CNS alteration were still under investigation. 2) No other infectious etiologies of microcephaly besides ZIKV were reported. 3) Short observation period of the study. 4) No description of how many cases of microcephaly alone there are in the study.	Very Low (outcome measurement bias, indirect evidence)
Vargas et al. 21	Metropolitan region of Recife, Pernambuco	Descriptive case series study	Report the first cases of microcephaly in NBs possibly related to ZIKV in Recife.	26/10/2015 to 19/11/2015	Live births with microcephaly among residents of the metropolitan region of Recife, composed of 14 municipalities.	40	40	100%	3 syphilis 1 herpes simplex 1 CMV 35 ZIKV	7.5% 2.5% 2.5% 87.5%	1) Difficulty of mothers to report likely exposure to signs and symptoms during pregnancy. 2) High proportion of loss. 3) Lack of opportunity for laboratory diagnosis. 4) Unavailability of imaging and serological testing for TORCH in all cases. 5) Two changes of microcephaly classification criteria after the data survey.	Very Low (case series)
Cabral et al.22	Sergipe State	Descriptive case series study	Describe clinical and epidemiological characteristics of microcephaly cases in live births in Sergipe and calculate the prevalence in its municipalities.	01/09/2015 to 30/11/2015	Live births with microcephaly notified to the SES of Sergipe and reported in health services as cases of microcephaly through active search.	60	17	28.0%	5 Toxoplasmosis 3 Syphilis 1 CMV 8 Not informed**	29.5% 17.5% 6.0% 47.0%	1) Divergence or absence of information in medical records, which may have decreased the accuracy of epidemiological description. 2) Difficulty of mothers in reporting signs and symptoms. 3) Absence of clinical sample collection to identify ZIKV in mothers and children. 4) Failure to measure the cephalic circumference of those born of normal birth after 24 hours, which may have overestimated the number of microcephaly cases. 5) Lack of data to assess whether the live birth was small for gestational age, a situation in which reduced head circumference may not represent microcephaly.	Very low (case series. Memory bias, registration bias)
Martins et al.23	Sao Paulo State	Descriptive case series study	Characterize cases of congenital syndrome associated with ZIKV infection and other etiologies	30/10/2015 to 30/06/2017	Suspected cases of microcephaly reported to RESP	Not informed***	9	_	9 ZIKV	_	1) Incomplete information inherent to surveillance. 2) Lack of punctuality in the collection of clinical samples to allow the identification of ZIKV in mothers and children. 3) High laboratory specificity, using only RT-PCR for diagnosis of ZIKV in pregnant women, because serology was not available at the time of investigation. 4) Lack of complete investigation of TORCH for all cases.	Very Low (outcome measurement bias, indirect evidence)
Almeida et al. 24	Piaui State	Descriptive case series study	Describe microcephaly epidemic aspects in Piaui State.	08/11/2015 to 31/12/2016	NBs submitted to the investigation protocol of the Regional Reference Center for microcephaly in the period of the ZIKV epidemic.	97	Not informed***	_	5 CMV 8 dengue 6 chikungunya 3 syphilis 5 herpes simplex	5.0% 5.0% 8.0% 6.0% 3.0%	1) Criteria for confirmation of reported cases were the presence of clinical, laboratory and radiological findings compatible with CNS malformation, however, there is no adequate description in the methodology. 2) It is possible that a small proportion of cases were not caused by congenital ZIKV infection because of positive serology for other infections. 3) There are no laboratory confirmation results of ZIKV infections (68 with negative PCR)	Very Low (outcome measurement bias, indirect evidence)
Ribeiro et al.25	Piaui State	Descriptive population-based study,	Describe the occurrence and characteristics of microcephaly cases during the ZIKV epidemic	01/2015 to 01/2016	Infection-related cases of microcephaly among live births reported through SINASC and/or RESP	75	34	45.3%	1 dengue 1 chikungunya 1 Toxoplasmosis 11 syphilis 20 ZIKV *** (1 confirmation during pregnancy)	3.3% 3.3% 3.3% 30% 60%*** (5% of cases)	1) Difficulty in gathering information due to problems in reading medical records or lack of data, impairing the classification of cases (mainly regarding maternal sample collection during gestation and postpartum) and reducing the number of cases that could be analyzed: 21 newborns with data, out of 75 investigated. 2) Difficulty in diagnosing infectious processes, due to different window opportunities for sample collection in both live births and mothers, which did not allow an accurate understanding onwhether the mother's infection reached the fetus.	Very Low (outcome measurement bias, indirect evidence)
Araújo et al.26	Pernambuco State	Case-control study	Assess the association between microcephaly and congenital Zika virus infection, along with a comprehensive investigation of other potential risk factors in an epidemic context in Pernambuco State, Brazil.	15/01/2016 to 30/11/2016	Study population of neonates from women residing in Pernambuco, Brazil, who delivered in eight public maternity hospitals in Recife. Cases were neonates with microcephaly (live births or stillbirths). Controls were live neonates without microcephaly and with no brain abnormalities and no major birth defects,	91	43	47.2%	43 ZIKV	100%	Information on exposures during the gestational period was reported by the mothers and, therefore, might be subject to recall bias	Low (Case-control, memory bias, registration bias)
Rocha et al. 27	Ceara State	Case-control study	To identify factors associated with microcephaly diagnosis in NBs	10/2015 to 06/2017	Children who received both clinical and imaging diagnoses of microcephaly (cases) and children without microcephaly identified in the vicinity of each case's residence (controls).	57	36	63.2%	27 ZIKV 1 syphilis 1 dengue 1 chikungunya 2 toxoplasmosis 2 CMV 2 herpes simplex	75% 2.8% 2.8% 2.8% 5.5% 5.5% 5.5%	Data were collected retrospectively for cases and controls.	Low (Case-control, memory bias, registration bias)
Herber et al. 28	Rio Grande do Sul State	Cross-sectional study	To identify causes of congenital microcephaly in Rio Grande do Sul State, a region where no ZIKV outbreak had been reported	01/12/2015 to 31/12/2017	NBs with microcephaly at birth with data obtained from the RESP	148	29	20%	3 ZIKV 6 CMV 7 toxoplasmosis 13 syphilis	10.0% 20.0% 25.0% 45.0%	1) Microcephaly criteria changed during the study. 2) Use of retrospective data susceptible to information bias. 3) Impossibility to establish the gestational period when most infections occurred, to compare with the clinical findings of NBs. 4) Study developed during a period of modification of the MS guidelines regarding the diagnostic criteria for microcephaly;healthcare professionals need to identify a disease was not yet known. 5) Brain imaging tests such as MRI were not easily accessible for the study population	Low (Cross-sectional bias transversal, memory and registrations bias)

*presence of microcephaly or other CNS disorders (includes microcephalia and other diagnostic criteria for CZS , but does not discriminate total microcephaly cases ); **there is no such data in the study; ***diagnosis of ZIKV by epidemiologic relationship during ESPII; ZIKV = Zika virus; NB = newborn; SINASC = Live Births Information System; CNS = central nervous system; MS = Ministry of Health; CMV = cytomegalovirus; SES = State Department of Health; RT-PCR = reverse-transcriptase polymerase chain reaction; RESP = Public Health Events Registry