Identifying birth defects in automated data sources in the Vaccine Safety Datalink

Validation of ICD-9-CM codes for major genitourinary birth defects in Military Health System administrative data, 2006-2014

BACKGROUND

The Department of Defense Birth and Infant Health Research program is dedicated to birth defects research and surveillance among military families. Here, we assess and refine the validity of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for selected genitourinary birth defects in the Military Health System (MHS). We additionally outline methods for the calculation of positive predictive value (PPV) and negative predictive value (NPV), sensitivity, and specificity using a stratified sampling design.

METHODS

Among military infants born from 2006 through 2014, a random sample of ICD-9-CM screen-positive cases (for six genitourinary birth defects) and screen-negative cases were selected for chart review. PPV, NPV, sensitivity, and specificity were calculated for individual defects and any included defect (i.e., overall); measures were weighted by the inverse probability of being sampled.

RESULTS

Of 461,557 infants, 686 were sampled for chart review. Bladder exstrophy was accurately reported (PPV: >90%), while the accuracy of renal dysplasia, renal agenesis/hypoplasia, and hypospadias was moderate (PPVs: 66%-68%) and congenital hydronephrosis was low (PPV: 20%). Specificity and NPVs always exceeded 98%. The overall PPV was 50%; however, excluding congenital hydronephrosis screen-positive cases and requiring at least two inpatient or outpatient diagnostic codes resulted in a PPV of 85%.

CONCLUSIONS

The validity of major genitourinary birth defect codes varied in MHS administrative data. The accuracy of an overall defect measure improved by omitting congenital hydronephrosis and requiring at least two diagnostic codes. Although PPV is generally useful for research, additional calculation of NPV, sensitivity, and specificity better informs the identification of appropriate selection criteria across surveillance and research settings.

Validation of case definition algorithms for the ascertainment of congenital anomalies

BACKGROUND

Congenital anomalies (CA) are one of the leading causes of infant mortality and long-term disability. Many jurisdictions rely on health administrative data to monitor these conditions. Case definition algorithms can be used to monitor CA; however, validation of these algorithms is needed to understand the strengths and limitations of the data. This study aimed to validate case definition algorithms used in a CA surveillance system in British Columbia (BC), Canada.

METHODS

A cohort of births between March 2000 and April 2002 in BC was linked to the Health Status Registry (HSR) and the BC Congenital Anomalies Surveillance System (BCCASS) to identify cases and non-cases of specific anomalies within each surveillance system. Measures of algorithm performance were calculated for each CA using the HSR as the reference standard. Agreement between both databases was calculated using kappa coefficient. The modified Standards for Reporting Diagnostic Accuracy guidelines were used to enhance the quality of the study.

RESULTS

Measures of algorithm performance varied by condition. Positive predictive value (PPV) ranged between approximately 73%-100%. Sensitivity was lower than PPV for most conditions. Internal congenital anomalies or conditions not easily identifiable at birth had the lowest sensitivity. Specificity and negative predictive value exceeded 99% for all algorithms.

CONCLUSION

Case definition algorithms may be used to monitor CA at the population level. Accuracy of algorithms is higher for conditions that are easily identified at birth. Jurisdictions with similar administrative data may benefit from using validated case definitions for CA surveillance as this facilitates cross-jurisdictional comparison.

Pregnancy and posttraumatic stress disorder: associations with infant outcomes and prenatal care utilization

BACKGROUND

Posttraumatic stress disorder (PTSD) affects 3.6-9.7% of women, and has been associated with adverse outcomes in pregnancy; however, associations with prenatal care (PNC) utilization are not clear.

OBJECTIVE

To evaluate associations of PTSD in pregnancy with PNC utilization and adverse infant outcomes in an active-duty military population (a population with universal health insurance).

METHODS

This was a retrospective cohort study of pregnant active-duty service members in Department of Defense Birth and Infant Health Research program data from 2007 to 2014. Administrative medical encounter data were used to define PTSD cases and outcomes of interest. Descriptive statistics and multivariable log-binomial regression compared PNC utilization and adverse infant outcomes (preterm birth, small for gestational age [SGA], major birth defects) among service members with current PTSD (defined as PTSD in the year prior to pregnancy or during pregnancy) to those without current PTSD.

RESULTS

Of the 103,221 singleton live births identified, 1657 (1.6%) were born to active-duty service members diagnosed with current PTSD. Service members with PTSD were more likely to initiate PNC in the first trimester (93.5% vs. 90.2%) and score adequate plus on the Adequacy of Prenatal Care Utilization Index (63.2% vs. 40.0%) compared to service members without PTSD. PTSD case status was not associated with preterm birth, SGA, or major birth defects, regardless of the adjustment set used (fully adjusted RR 0.96, 95% CI 0.82-1.13; RR 1.08, 95% CI 0.79-1.48; and RR 1.03, 95% CI 0.79-1.34, respectively).

CONCLUSION

For pregnant service members with current PTSD, no associations with adverse infant outcomes were noted, and these patients initiated care earlier and had higher PNC utilization scores compared to pregnant service members without current PTSD. Universal health care coverage and utilization of PNC in this population may mitigate adverse pregnancy outcomes observed in civilian populations of patients with PTSD.

Association of Inadvertent 9-Valent Human Papillomavirus Vaccine in Pregnancy With Spontaneous Abortion and Adverse Birth Outcomes

IMPORTANCE

The 9-valent human papillomavirus (9vHPV) vaccine is recommended for individuals through age 26 years and may be administered to women up to age 45 years. Data on 9vHPV vaccine exposures during pregnancy are limited.

OBJECTIVE

To evaluate the associations between 9vHPV vaccine exposures during pregnancy or peripregnancy and selected pregnancy and birth outcomes (spontaneous abortion [SAB], preterm birth, small-for-gestational age [SGA] birth, and major structural birth defect).

DESIGN, SETTING, AND PARTICIPANTS

This cohort study analyzed data from 7 participating health systems in the Vaccine Safety Datalink. The cohort comprised pregnancies among girls and women aged 12 to 28 years that ended between October 26, 2015, and November 15, 2018. Singleton pregnancies that ended in a live birth, stillbirth, or SAB were included.

EXPOSURES

Vaccine exposure windows were distal (9vHPV or 4vHPV vaccine administered from 22 to 16 weeks before last menstrual period [LMP]), peripregnancy (9vHPV vaccine administered from 42 days before LMP until LMP), and during pregnancy (9vHPV vaccine administered from LMP to 19 completed weeks' gestation). Primary comparisons were (1) girls and women with 9vHPV vaccine exposures during pregnancy vs those with 4vHPV or 9vHPV distal vaccine exposures, (2) girls and women with vaccine exposures peripregnancy vs those with 4vHPV or 9vHPV distal vaccine exposures, and (3) girls and women with 9vHPV vaccine exposures during pregnancy or peripregnancy vs those with 4vHPV or 9vHPV distal vaccine exposure.

MAIN OUTCOMES AND MEASURES

Spontaneous abortions were confirmed based on medical record review and adjudication. Preterm and SGA births were identified from electronic health record and birth data. Major structural birth defects were based on diagnostic codes using a validated algorithm. Inverse probability weighting was used to balance the covariates. Time-dependent covariate Cox proportional hazards regression models and Poisson regression were used to estimate the associations between 9vHPV vaccine exposures and pregnancy and birth outcomes.

RESULTS

The final cohort included 1493 pregnancies among girls and women with a mean (SD) maternal age of 23.9 (2.9) years. Of these pregnancies, 445 (29.8%) had exposures to the 9vHPV vaccine during pregnancy, 496 (33.2%) had exposures to the 9vHPV vaccine peripregnancy, and 552 (37.0%) had 4vHPV or 9vHPV distal vaccine exposures. The 9vHPV vaccine administered during pregnancy was not associated with increased risk for SAB (hazard ratio, 1.12; 95% CI, 0.66-1.93) compared with distal vaccine exposures. Findings were similar for 9vHPV vaccine exposures peripregnancy (relative risk [RR], 0.72; 95% CI, 0.42-1.24). Among live births (n = 1409), 9vHPV vaccine exposures during pregnancy were not associated with increased risks for preterm birth (RR, 0.73; 95% CI, 0.44-1.20) or SGA birth (RR, 1.31; 95% CI, 0.78-2.20). Results were similar regarding the association between 9vHPV vaccine exposures peripregnancy and preterm birth (RR, 0.72; 95% CI, 0.45-1.17) and SGA birth (RR, 1.10; 95% CI, 0.65-1.88). Birth defects were rare in all exposure groups, occurring in about 1% of live births with available infant data.

CONCLUSIONS AND RELEVANCE

This study found that 9vHPV vaccine exposures during or around the time of pregnancy were uncommon and not associated with SABs or selected adverse birth outcomes. These findings can inform counseling for inadvertent 9vHPV vaccine exposures.

Developing algorithms for identifying major structural birth defects using automated electronic health data

PURPOSE

Given the 2015 transition to International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) diagnostic coding, updates to our previously published algorithms for major structural birth defects (BDs) were necessary. Aims of this study were to update, validate, and refine algorithms for identifying selected BDs, and then to use these algorithms to describe BD prevalence in the vaccine safety datalink (VSD) population.

METHODS

We converted our ICD-9-CM list of selected BDs to ICD-10-CM using available crosswalks with manual review of codes. We identified, chart reviewed, and adjudicated a sample of infants in the VSD with ≥2 ICD-10-CM diagnoses for one of seven common BDs. Positive predictive values (PPVs) were calculated; for BDs with suboptimal PPV, algorithms were refined. Final automated algorithms were applied to a cohort of live births delivered 10/1/2015-9/30/2017 at eight VSD sites to estimate BD prevalence. This research was approved by the HealthPartners Institutional Review Board, by all participating VSD sites, and by the CDC, with a waiver of informed consent.

RESULTS

Of 573 infants with ≥2 diagnoses for a targeted BD, on adjudication, we classified 399 (69.6%) as probable cases, 31 (5.4%) as possible cases and 143 (25.0%) as not having the targeted BD. PPVs for the final BD algorithms ranged from 0.76 (hypospadias) to 1.0 (gastroschisis). Among 212 857 births over 2 years following transition to ICD-10-CM coding, prevalence for the full list of selected defects in the VSD was 1.8%.

CONCLUSIONS

Algorithms can identify infants with selected BDs using automated healthcare data with reasonable accuracy. Our updated algorithms can be used in observational studies of maternal vaccine safety and may be adapted for use in other surveillance systems.

Safety of yellow fever vaccination in pregnancy: findings from a cohort of active duty US military women

BACKGROUND

Yellow fever (YF) is a rare viral disease that can be prevented through receipt of a live attenuated vaccine. In the US military, service members must receive the YF vaccine before assignment to endemic areas, putting active duty service women at heightened risk for inadvertent exposure during preconception or pregnancy. Few studies have investigated the safety of YF vaccination in pregnancy to date, and none in a military population.

METHODS

Department of Defense Birth and Infant Health Research program data were used to identify pregnancies and infants among active duty US military women, 2003-2014. Multivariable regression models estimated associations with YF vaccine exposure during preconception/pregnancy and adverse outcomes (e.g. spontaneous abortion, birth defects). Sensitivity analyses were performed that excluded pregnancies exposed to other live vaccines. For analyses of birth defects only, a secondary sensitivity analysis was performed that excluded infants diagnosed with chromosomal anomalies.

RESULTS

Of the 196 802 pregnancies and 160 706 singleton infants identified, 1347 (0.7%) and 1132 (0.7%), respectively, were exposed to the YF vaccine. No increased risks for adverse pregnancy or infant outcomes were observed in the main analysis. In sensitivity analyses that excluded pregnancies exposed to other live vaccines, preconception YF vaccine exposure was associated with birth defects [adjusted risk ratio (aRR) = 1.71, 95% confidence interval (CI) = 1.08-2.73]; this association was attenuated when further excluding infants with chromosomal anomalies (aRR = 1.59, 95% CI = 0.97-2.62).

CONCLUSIONS

Overall, YF vaccine exposure did not appear to be associated with most adverse outcomes among this population of pregnant military women. A tenuous association between preconception YF vaccine exposure and birth defects was observed in sensitivity analyses, which may warrant further investigation.

Maternal and infant outcomes following exposure to quadrivalent human papillomavirus vaccine during pregnancy

INTRODUCTION

The Department of Defense encourages service members ≤26 years of age to receive the human papillomavirus (HPV) vaccine. Although this vaccine is not recommended in pregnancy, inadvertent vaccination may occur. The objective of this study was to assess whether active duty US military women who received the quadrivalent HPV vaccine (4vHPV) during pregnancy were at increased risk for adverse maternal or infant outcomes.

METHODS

The study population included active duty US military women aged 17-28 years with at least one pregnancy between 2007 and 2014, and the infants resulting from those pregnancies. Pregnancies, live births, and outcomes were identified using medical codes in administrative medical records. Exposure to 4vHPV during pregnancy was ascertained from personnel immunization records. Multivariable regression models were used to calculate risk estimates and 95% confidence intervals for the maternal outcomes of spontaneous abortion, preeclampsia/eclampsia and preterm labor, and the infant outcomes of preterm birth, birth defects, growth problems in infancy or in utero, and infant sex.

RESULTS

Overall, 90,600 pregnancies and 75,670 singleton infants were identified. Approximately 2% of pregnancies and infants were exposed to 4vHPV during pregnancy. After adjustments, no positive associations were detected between inadvertent exposure to 4vHPV during pregnancy and any adverse pregnancy or infant outcomes.

DISCUSSION

Our findings add to an established body of literature demonstrating the safety of 4vHPV when inadvertently administered during pregnancy. Although 4vHPV is no longer administered in the US, its use continues overseas; therefore, safety studies remain important. Furthermore, such studies can provide reassurance to women inadvertently exposed to nonavalent HPV vaccine (9vHPV) in pregnancy, which protects against four of the same antigens as 4vHPV, since safety of 9vHPV has not yet been established in pregnant women.

Japanese encephalitis vaccination in pregnancy among U.S. active duty military women

INTRODUCTION

Japanese encephalitis (JE) vaccine is an inactivated vaccine that has shown no risks in pregnancy in animal models, but epidemiologic studies are lacking. U.S. military service members located in JE endemic regions are required to be vaccinated; understanding the potential adverse events (AEs), including AEs that may occur in pregnancy, is needed. Here, we assessed pregnancy and infant health outcomes in association with JE vaccination in pregnancy.

METHODS

The study population consisted of 192,570 pregnancies to active duty women (2003-2014), captured in the Department of Defense Birth and Infant Health Research program. JE vaccine in pregnancy, vaccine count, formulation, trimester, and whether first career dose coincided with pregnancy were compared with unexposed pregnancies to assess risk of pregnancy and infant health outcomes. Adjusted risk estimates and 95% confidence intervals (CIs) were calculated by multivariable models.

RESULTS

Of the 192,570 identifed pregnancies, 513 were exposed to the JE vaccine; 474 exposures occurred in the first trimester. For all outcomes, elevated risk estimates ranging from 1.53 to 1.70, were observed with receipt of >1 JE vaccine in pregnancy, though 95% CIs were wide and encompassed the null. First dose of JE vaccination in pregnancy was associated with a 1.87 (95% CI: 1.12-3.13) times increased risk of low birthweight (LBW) when excluding pregnancies exposed to other non-routinely recommended vaccinations in pregnancy. All other associations were null in both main and subset analyses.

CONCLUSIONS

The overall results of these analyses provide reassuring findings for the safety of JE vaccination in pregnancy. Higher counts of JE vaccine received in pregnancy yielded large yet non-statistically significant risk estimates for all outcomes, though likely driven by lack of pregnancy awareness. An association was observed with LBW in subset analyses, but it was limited to women receiving their first JE vaccine and not observed in the larger main analyses.

Infant health outcomes among offspring of male U.S. military divers

While there are suggestions that the extreme hyperbaric conditions encountered during deep saturation diving may impact male reproductive function, few studies have investigated whether paternal occupational diving influences offspring health outcomes. To examine this, Department of Defense Birth and Infant Health Research program data were used to identify the offspring of male active duty divers and non-divers in the U.S. military, 2001-2016. Log-binomial regression models estimated associations with infant outcomes (e.g., major structural birth defects, low birthweight). Among 1,148,252 identified singleton infants, 3,843 were considered the offspring of male divers; paternal occupational diving was not positively associated with any adverse infant outcome under study. These findings corroborate existing literature and further suggest that male divers in the U.S. military are not occupationally exposed to reproductive hazards that adversely influence offspring infant health outcomes.

Birth and early developmental screening outcomes associated with cannabis exposure during pregnancy

OBJECTIVE

To compare birth and early developmental screening outcomes for infants with and without in utero cannabis exposures.

STUDY DESIGN

Observational cohort of women receiving prenatal care within a large health system, live birth between October 1, 2015 and December 1, 2017, and at least one infant visit. Cannabis exposure was through routine urine toxicology screen. Preterm birth, small for gestational age (SGA) birth, birth defects, and early developmental screening outcomes were assessed from birth and electronic health record data.

RESULTS

Of 3435 women, 283 (8.2%) had a positive urine toxicology screen. In utero cannabis exposure was associated with SGA birth, adjusted rate ratio (aRR) 1.69 (95% confidence interval [CI]: 1.22-2.34). Abnormal 12-month developmental screens occurred in 9.1% of infants with in utero cannabis exposure vs. 3.6% of those with negative maternal screens, aRR 1.90 (95% CI: 0.92-3.91). Additional birth outcomes were not associated with in utero cannabis exposure.

CONCLUSIONS

Exposure to cannabis during pregnancy may adversely impact fetal growth.

Safety of tetanus, diphtheria, and acellular pertussis vaccination among pregnant active duty U.S. military women

BACKGROUND

The tetanus, diphtheria, and acellular pertussis (Tdap) vaccine was approved for U.S. adults in 2005 and recommended for administration in every pregnancy in 2012, with optimal timing between 27 and 36 weeks' gestation. In the military, however, a current Tdap vaccination status is compulsory for service, and active duty women may be inadvertently exposed in early pregnancy. Safety data in this population are limited.

OBJECTIVES

To assess safety of inadvertent (0-13 weeks' gestation) and recommended (27-36 weeks' gestation) exposure to the Tdap vaccine in pregnancy.

METHODS

Pregnancies and live births from Department of Defense Birth and Infant Health Research program data were linked with military personnel immunization records to determine pregnancy Tdap vaccine exposure among active duty women, 2006-2014. Multivariable Cox and generalized linear regression models estimated associations between Tdap vaccine exposure and adverse pregnancy or infant outcomes.

RESULTS

Of 145,883 pregnancies, 1272 were exposed to the Tdap vaccine in the first trimester and 9438 between 27 and 36 weeks' gestation. Neither inadvertent nor recommended vaccine exposure were associated with spontaneous abortion, preeclampsia, or preterm labor. Among 117,724 live born infants, 984 were exposed to the Tdap vaccine in the first trimester and 9352 between 27 and 36 weeks' gestation. First trimester exposure was not associated with birth defects, growth problems in utero, growth problems in infancy, preterm birth, or low birth weight. Tdap vaccine exposure between 27 and 36 weeks' gestation was not associated with any adverse infant outcome.

CONCLUSIONS

Among a population of active duty women in the U.S. military who received the Tdap vaccine during pregnancy, we detected no increased risks for adverse maternal, fetal, or infant outcomes. Our findings corroborate existing literature on the safety of exposure to the Tdap vaccine in pregnancy.

Atovaquone-proguanil exposure in pregnancy and risk for adverse fetal and infant outcomes: A retrospective analysis

BACKGROUND

Malaria in pregnancy can cause severe maternal and fetal complications. Chloroquine (CQ) and mefloquine (MQ) are recommended for chemoprophylaxis in pregnancy, but are not always suitable. Atovaquone-proguanil (AP) might be a viable option for malaria prevention in pregnancy, but more safety data are needed.

METHODS

Data for pregnancies and live births among active duty military women, 2003-2014, from the Department of Defense Birth and Infant Health Research program were linked with pharmacy data to determine antimalarial exposure. Multivariable Cox and logistic regression models were used to assess the relationship of antimalarial exposure with fetal and infant outcomes, respectively.

RESULTS

Among 198,164 pregnancies, 50 were exposed to AP, 156 to MQ, and 131 to CQ. Overall, 17.6% of unexposed pregnancies and 28.0%, 16.0%, and 6.1% of pregnancies exposed to AP, MQ, and CQ, respectively, ended in fetal loss (spontaneous abortion or stillbirth) (adjusted hazard ratios [aHR] = 1.46, 95% confidence interval [CI] 0.87-2.46; aHR = 1.06, 95% CI 0.72-1.57; and aHR = 0.47, 95% CI 0.24-0.94, respectively).

CONCLUSIONS

The small number of AP exposed pregnancies highlights the difficulty in assessing safety. While definitive conclusions are not possible, these data suggest further research of AP exposure in pregnancy and fetal loss is warranted.

TWITTER LINE

More research on fetal loss following atovaquone-proguanil exposure in pregnancy is warranted.

Postlicensure safety surveillance of congenital anomaly and miscarriage among pregnancies exposed to quadrivalent human papillomavirus vaccine

Limited safety data are available on inadvertent exposure to quadrivalent human papillomavirus vaccine (4vHPV) during pregnancy. We conducted a descriptive observational postlicensure safety surveillance study in Kaiser Permanente Southern California and Northern California to assess congenital anomaly and miscarriage among pregnancies exposed to 4vHPV. Using electronic medical records, we identified women who received a dose of 4vHPV between August 2006 and March 2008 within 30 days preconception or any time during a possible pregnancy. A broad algorithm was developed using diagnostic and procedure codes and laboratory tests to identify pregnancy, congenital anomalies, and miscarriages. Medical records of all potential congenital anomaly cases and a random sample of 100 potential miscarriage cases were reviewed to confirm pregnancy exposure and diagnosis. Results were reviewed by an independent Safety Review Committee (SRC). Among the population of 189,629 females who received at least one dose of 4vHPV during the study period, 2,678 females were identified as possibly having a 4vHPV-exposed pregnancy. Among 170 potential congenital anomalies identified, 44 (26%) were found to be both 4vHPV-exposed and confirmed congenital anomaly cases. Among the 633 potential miscarriages identified, the records of a random sample of 100 cases were reviewed, and 9 cases (9%) were confirmed as 4vHPV-exposed miscarriages. The SRC noted no safety signal for congenital anomaly or miscarriage associated with 4vHPV exposure during pregnancy. The rate of major congenital anomaly (3.6%) was in the range of background estimates from the literature. There was no apparent pattern of timing of 4vHPV exposure among 4vHPV-exposed miscarriages.

Maternal and Infant Outcomes After Human Papillomavirus Vaccination in the Periconceptional Period or During Pregnancy

OBJECTIVE

To evaluate whether quadrivalent human papillomavirus vaccine (4vHPV) administered during the periconceptional period or during pregnancy was associated with increased risks for adverse obstetric events, adverse birth outcomes, or selected major structural birth defects.

METHODS

We conducted a retrospective, observational cohort study using administrative and health care data from the Vaccine Safety Datalink. Insured women 13-27 years old with singleton pregnancies and a live birth from January 1, 2007, through September 1, 2013, who received 4vHPV during the periconceptional period (2 weeks before to 2 weeks after their last menstrual period), during pregnancy, or during both periods combined were compared with women who had a live birth during the same time period and received 4vHPV 4-18 months before their last menstrual period. We examined risks of gestational diabetes, hypertensive disorders of pregnancy, chorioamnionitis, preterm birth, small-for-gestational-age birth, and selected major structural birth defects in offspring. We estimated relative risks associated with receipt of 4vHPV during the periconceptional period, during pregnancy, and both exposure periods combined using a generalized linear model with Poisson distribution including a propensity score that included relevant maternal demographic and pregnancy characteristics.

RESULTS

Of 92,579 potentially eligible pregnant women, 720 received 4vHPV during the periconceptional period, 638 received 4vHPV during pregnancy, and 8,196 received 4vHPV during the comparison period. Administration of 4vHPV during pregnancy was not associated with increased risk of adverse obstetric events, birth outcomes. Preterm birth occurred in 7.9% of pregnancies with vaccine exposures during pregnancy compared with 7.6% of pregnancies with vaccination in the comparison period (adjusted relative risk 0.97, 95% CI 0.72-1.3). Major structural birth defects were diagnosed in 2.0% of pregnancies with vaccine exposure during pregnancy compared with 1.8% of pregnancies with vaccine exposure during the comparison period (adjusted prevalence ratio 1.0, 95% CI 0.52-1.9). Results were similar for 4vHPV exposure during the periconceptional period.

CONCLUSION

Quadrivalent HPV vaccine inadvertently administered in pregnancy or during the periconceptional period was not associated with adverse pregnancy or birth outcomes.

First Trimester Influenza Vaccination and Risks for Major Structural Birth Defects in Offspring

OBJECTIVE

To examine risks for major structural birth defects in infants after first trimester inactivated influenza vaccine (IIV) exposures.

STUDY DESIGN

In this observational study, we used electronic health data from 7 Vaccine Safety Datalink sites to examine risks for selected major structural defects in infants after maternal IIV exposure. Vaccine exposures for women with continuous insurance enrollment through pregnancy who delivered singleton live births between 2004 and 2013 were identified from standardized files. Infants with continuous insurance enrollment were followed to 1 year of age. We excluded mother-infant pairs with other exposures that potentially increased their background risk for birth defects. Selected cardiac, orofacial or respiratory, neurologic, ophthalmologic or otologic, gastrointestinal, genitourinary and muscular or limb defects were identified from diagnostic codes in infant medical records using validated algorithms. Propensity score adjusted generalized estimating equations were used to estimate prevalence ratios (PRs).

RESULTS

We identified 52 856 infants with maternal first trimester IIV exposure and 373 088 infants whose mothers were unexposed to IIV during first trimester. Prevalence (per 100 live births) for selected major structural birth defects was 1.6 among first trimester IIV exposed versus 1.5 among unexposed mothers. The adjusted PR was 1.02 (95% CI 0.94-1.10). Organ system-specific PRs were similar to the overall PR.

CONCLUSION

First trimester maternal IIV exposure was not associated with an increased risk for selected major structural birth defects in this large cohort of singleton live births.