Table 1: Characteristics of included studies.

ReferencesCountryInclusion criteriaGestational age at sample collection (weeks)Examined tissue typeSample sizeHPV prevalence%HPV detection method Study quality
Study strengthsPotential biases

[34]KoreaPregnant women
healthy, ≥18 years of age, sonographically confirmed intrauterine pregnancy
1st, 2nd, or 3rd trimester or postpartumCervixTotal: 960
1st trimester: 380
2nd trimester: 193
3rd trimester: 195
Postpartum: 192
Total: 24.3
1st trimester: 20.5
2nd trimester: 34.2
3rd trimester: 23.1
Postpartum: 22.9
DNA chipLarge cohort, multivariant logistic regression analysis, separate analysis for trimestersSample collection at different time points, including women with abnormal pap smear

[35]KoreaPD
healthy, <37 weeks of gestation
6-week postpartumCervix4515.6HCAMultivariant logistic regression analysisSmall sample size, postpartum sampling only, HCA sensitivity limited to 13 HPV-types

[36]MexicoSA: healthy, curettage up to week 20
ND: healthy, attending for delivery at term with viable products
SA: <20
ND: before delivery
CervixSA: 139
ND: 138
SA: 24.4
ND: 15.2
PCRLarge cohort, risk analysisComparison of SA (first trimester) with ND (at term), HPV-related disease history unclear

[37]KoreaPregnant women
healthy, singleton, in first trimester
Cervix: 1st, 2nd, and 3rd trimester, postpartum
Placenta, umbilical cord blood: at birth
Cervix, placenta, umbilical cord bloodCervix: 153
Placenta: 152
Cervix: 24
Placenta: 3.3
Umbilical cord blood: 1.3
DNA chipLarge cohort, longitudinal follow-up, multivariant logistic regression analysisSample collection from cervix at different time points

[38]PolandPregnant women
singleton, normal cervical smear
33–41Cervix13516.3PCRLarge cohort, multivariant logistic regression analysis, confirmation by sequencingVaginal and cesarean deliveries included, potential contamination problem (HPV11 present in all positive samples)

[23]KoreaPregnant women
healthy, over 36 weeks of gestation
>36Cervix, placenta, umbilical cord blood469Cervix: 15.4
Placenta: 0
Umbilical cord blood: 0
DNA chipLarge cohort, confirmation by in situ hybridizationVaginal and cesarean deliveries included Umbilical cord blood and placenta were collected from HPV positive mothers

[39]ChinaPregnant women
healthy, asymptomatic
22.5–26.7Cervix313913.4DNA chipLarge cohort, logistic regression analysisVaginal and cesarean deliveries included, women with abnormal cervical cytology included

[40]NetherlandsPregnant women
NA
1st, 2nd, and 3rd trimester, postpartumCervix5121.6PCRMatched groups, detection method with high analytical sensitivitySmall sample size, self-sampling, sample collection at different time points

[41]KoreaPregnant women
healthy, over 36 weeks of gestation
>36Cervix29118.9DNA chipLarge cohort, stratified analysis to test for confoundingWomen with abnormal cervical cytology included, vaginal and cesarean deliveries included

[42]FinlandPregnant women
healthy, in third trimester
3rd trimester, at birthCervix, placenta, umbilical cord bloodCervix: 329
Placenta: 306
Umbilical cord: 311
Cervix: 16.4
Placenta: 4.2
Umbilical cord blood: 3.5
PCRLarge cohort, regression analysis, multimetrix assay for HPV detection, pap smear at baseline

[43]PolandSA: healthy
ND: healthy, delivering at term
SA: 6–16
ND: at birth
Aborted products of conception, placentaSA: 51
ND: 78
SA: 17.7
ND: 24.4
PCRSmall sample size, comparison of SA with ND, HPV-related disease history unclear

[44]MexicoPregnant women
healthy, in third trimester, delivering at term
3rd trimesterCervix, placenta72Cervix: 75
Placenta: 47.2
PCRPCR process was blindedPotential contamination problem (HPV18 present in all positive placenta samples), vaginal and cesarean deliveries included

[45]LithuaniaPregnant women
NA
1st and 3rd trimesterCervix1st trimester: 213
3rd trimester: 146
1st trimester: 17.8
3rd trimester: 10.3
PCRLarge cohort, risk analysis, separate analysis for trimestersBig proportion with history of gynecological diseases, exclusion of 67 women due to change of residency/miscarriage/ premature delivery, no inclusion and exclusion criteria, commercial HPV PCR kit

[46]JapanPregnant women
NA
1st, 2nd, or 3rd trimester or postpartumCervix15135.8PCRLarge cohort, pap smear at study entrySample collection at different time points, unclear how and when women deliver

[21]USAPD
<37 weeks of gestation, available HPV-test results
NACervix7067.1HCARisk analysis (age, race), data from over 11 yearsSampling method and time point not mentioned, study including African Americans, HCA restricted to 13 HPV-types only

[47]TurkeyPregnant women
NA
18–22Cervix1342.2PCRLarge cohort22 with abnormal ultrasound findings, other virus types being in focus, HPV-related disease history unclear, no inclusion and exclusion criteria, outpatient clinic (low socioeconomic group)

[32]BelgiumPregnant women
assigned for abdominal CVS, mainly due to high risk for chromosomal abnormalities
11–13Placenta355.7PCRTransabdominal sampling (no birth canal contamination), highly sensitive detection method, confirmation by sequencingSmall sample size, highly selected group of women, limited amount of placenta material (actual HPV prevalence higher?), HPV-related disease history unclear

[48]USAPregnant women
healthy, in third trimester, 18 and above
3rd trimesterCervix33328PCRLarge cohort, logistic regression analysis, confirmation by sequencingVaginal and cesarean deliveries included, unclear if deliveries are at term, 25% of women with history of HPV-related lesions

[49]BrazilPregnant women
NA
2–37Cervix37135.3HCALarge cohort, multivariant logistic regression analysisInclusion at ambulatories for patients suspected to infectious diseases, no inclusion and exclusion criteria, sample collection at different time points, women with genital warts included

[50]BrazilPregnant women
NA
NACervix4025PCRSmall sample size, inclusion at outpatient clinic (low socioeconomic group), no inclusion and exclusion criteria, HPV-related disease history unclear, sampling time point not mentioned

[51]SpainPregnant women
unselected
29–33Cervix8286.5PCRLarge cohort, multivariant logistic regression analysisGoal to find HPV positive women for prospective cohort study on mother-to-child transmission, HPV-related disease history unclear, no inclusion and exclusion criteria, vaginal and cesarean deliveries

[27]FinlandPregnant women
third trimester
31.6–42.5Placenta, Umbilical cord bloodPlacenta: 306
Umbilical cord blood: 311
Placenta: 4.2
Umbilical cord blood: 3.5
PCRLarge cohort, multivariant regression analysis, pap smear at study entry, confirmation by sequencingIncluded women delivering before week 37, part of women showing genital warts or cervical lesions, no HPV status examination before recruitment

[20]USAPD: spontaneous, <37 weeks of gestation
ND: delivering at term
PD: 21–36
ND: 37–42
PlacentaPD: 30
ND: 30
PD: 50
ND: 20
PCRComparison of PD to ND (best possible control), confirmation by sequencingSmall sample size, study including mostly African Americans, HPV-related disease history unclear, type-specific PCR only

[29]USASA: singleton, in second trimester
IA: singleton, for congenital anomalies or maternal medical indications
16.7–23.6PlacentaSA: 84
IA: 16
SA: 57
IA: 31
PCRMultivariable logistic regression analysis, comparison of SA to IA (best possible control), confirmation by sequencingSmall sample size, imbalance between cases and controls, study including African Americans, HPV-related disease history unclear, gestational age of controls being greater

[52]JapanPregnant women
healthy, unselected
1st, 2nd, or 3rd trimesterCervix118312.5PCRLarge cohortHPV-related disease history unclear, sample collection at different time points

[53]USAPregnant women
clinically indicating amniocentesis, intact membranes
NAAmniotic fluid1420PCRLarge cohort, transabdominal sampling (no birth canal contamination)HPV-related disease history unclear, sampling time point not mentioned, highly selected group of women, unclear how/when they deliver

[54]MexicoPregnant women
healthy
1st, 2nd, or 3rd trimesterCervix27437.1HCALarge cohort, unconditional/conditional logistic regressionSelf-sampling, HPV-related disease history unclear, sample collection at different time points, HCA restricted to 13 HR-types

[55]ChinaPregnant women
asymptomatic (cervical)
1st, 2nd, or 3rd trimesterCervix, amniotic fluid, umbilical cord blood116Cervix: 36.2PCRLarge cohortSample collection at different time points

[13]AustriaPregnant women
healthy, uncomplicated pregnancy, undergoing cesarean section
37.1–40.2Cervix, placenta, amniotic fluid, umbilical cord blood153Cervix: 36.6
Placenta: 5.2
Amniotic fluid: 0
Umbilical cord blood: 0
HCA, PCRLarge cohort, univariant/multivariant logistic regression analysisHighly selected group of women, placenta swabs (quality of material)

[56]USAPregnant women
unselected
35 and 39Cervix57729PCRLarge cohort, logistic regression analysis, confirmation by sequencing, pap smear at study entryNo inclusion and exclusion criteria, women with history of HPV-related lesions included

[28]CroatiaSA
normal cervix
4–19Placenta1087.4PCRLarge cohort, only women with normal cervix49.1% having a miscarriage before, 35.2% having abnormal karyotype, possible contamination due to curettage, positive results only with HPV16 and 18 specific primers

[57]ChinaPregnant women
unselected, regardless of sexual history or cervical disease
1st, 2nd, or 3rd trimesterCervix30810.1PCRLarge cohort, confirmation by sequencing, age-matched controlsSample collection at different time points, inclusion of women regardless of sexual history or cervical diseases

[22]AustriaPregnant women
assigned for CVS or placental biopsy
9.6–31.3Cervix, placentaCervix: 179
Placenta: 147
Cervix: 24.6
Placenta: 0
HCA, PCRLarge cohort, univariant/multivariant logistic regression analysis, transabdominal sampling (no birth canal contamination)Highly selected group of women, unusual PCR primers (E6), unclear how/when they delivered, analysis of placenta by PCR, cervix by HCA

[58]France, Switzerland, GermanyPregnant women
assigned for amniocentesis due to maternal or fetal abnormalities
14–25Amniotic fluid23812PCR, Southern blotLarge cohort, transabdominal sampling (no birth canal contamination), confirmation by Study strengthHighly selected group of women, HPV-related disease history unclear, samples collected in three countries, unclear how/when they deliver

[59]ItalyPregnant women
healthy, negative pap smear at first trimester
36–39Cervix7115.2PCRLarge cohort, pap smear at study entry, no history of HPV-related lesionsSampling method not mentioned, vaginal and cesarean deliveries

[60]GreeceSA
<20 weeks of gestation
6–20Aborted product of conception1020PCRLarge cohort11 women have had previous SA, 3 cases with other diseases, GP5/6 primer (low sensitivity?), HPV-related disease history unclear

[61]ChinaPregnant women
singleton
36–40Cervix30122.6PCRLarge cohort, confirmation by Study strengthStudy including vaginal and cesarean deliveries, women with abnormal pap smear included, used specific E6 PCR primers only

[62]France, GermanySA: NA
IA: for social indication
NAAborted product of conceptionSA: 27
IA: 1
SA: 70.4
IA: 100
PCRSmall sample size, HPV-related disease history unclear, sampling time point not mentioned, no inclusion and exclusion criteria, PCR primer with low sensitivity

[63]ItalyPregnant women
healthy, negative pap smear at entry
36–39Cervix7525.4PCRLarge cohort, control for confounders, logistic regression analysis, confirmation by Study strengthSampling method not mentioned

[64]FinlandPregnant women
healthy
At birthCervix8630.2PCRConfirmation by Study strength and sequencingPossible sampling error, contamination, multiple HPV infection, inclusion of women with signs of cervical HPV infection, vaginal and cesarean deliveries

[18]USASA and IA
first trimester
1st trimesterAborted product of conceptionSA: 25
IA: 15
SA: 60
IA: 20
PCRComparison of SA to IA (best possible control), confirmation by dot blot hybridizationSmall sample size, possible contamination from cervix and vagina, HPV-related disease history unclear

[65]USAPregnant women
healthy
NACervix11434.2Southern blotLarge cohort, logistic regression analysisHistory of CIN not used as exclusion criteria, sampling time point not mentioned, study mostly including African Americans and Hispanics, Bronx → low socioeconomic group, Southern Blot (HPV11, 16, 18 only), unclear how/when they deliver

[66]GermanyPregnant women
uncomplicated pregnancies
1st, 2nd, and 3rd trimester, postpartumCervix10813.9HCALarge cohort, logistic regression analysis, age-frequency matched controlsSpecimens instead of patients, sample collection at different time points, commercial HPV detection kit (6 HPV-types only)

[67]HungaryPregnant women
cytologically and colposcopically healthy
1st, 3rd trimester, postpartumCervix3931PCRCytologically and colposcopically healthy womenSmall sample size, 8 deliveries being preterm, HPV-related disease history unclear, sample collection at different time points, outpatient clinic → low socioeconomic group

[68]USAPregnant women
healthy, in first trimester, ≥18 years of age
1st trimesterCervix24531HCALarge cohort, univariant risk analysis/multiple logistic regression analysis, confirmation by Study strengthStudy including African-Americans, HCA sensitivity limited to 14 HPV-types

ND = normal deliveries, PD = preterm deliveries, IA = induced abortion, SA = spontaneous abortion.