Preterm birth rate after bivalent HPV vaccination: Registry-based follow-up of a randomized clinical trial

Does HPV vaccination during periconceptional or gestational period increase the risk of adverse pregnancy outcomes?-An updated systematic review and meta-analysis based on timing of vaccination

INTRODUCTION

The human papillomavirus (HPV) vaccine is crucial in preventing cervical cancer, and a significant number of women in 135 countries worldwide may have unknowingly received the vaccine during peri-pregnancy or pregnancy due to a lack of regular pregnancy testing. Previous studies on the safety of pregnancy outcomes with vaccination before and after pregnancy have not reached definitive conclusions. Thus, we subdivided the vaccination time frame and conducted an updated study to further examine whether exposure to the HPV vaccine during pregnancy or the periconceptional period increases the likelihood of adverse pregnancy outcomes.

MATERIAL AND METHODS

The clinical trials and cohort studies published before August 1, 2023, were retrieved from PubMed, Embase, Web of Science, and Cochrane Central Register of Controlled Trials. The Newcastle-Ottawa Scale and Cochrane risk of bias assessment tool were adopted to evaluate the risk of bias in the included studies. In addition, the quality assessment was carried out using the Review Manager 5.4 Software, and a meta-analysis was conducted using the Stata 16 Software.

RESULTS

Eleven studies were located. The results showed that receiving 4vHPV during the periconceptional or gestational period had no relationship with an increased risk of spontaneous abortion, stillbirth, preterm birth, birth defects, small for gestational age, and ectopic pregnancy. Neither receiving 2vHPV nor 9vHPV was associated with a higher risk of stillbirth, preterm birth, birth defects, small for gestational age, and ectopic pregnancy; however, receiving 2vHPV during the period from 45 days before last menstrual period (LMP) to LMP and 9vHPV during the period from 90 days before LMP to 45 days after LMP seemed to be related to an increased risk of spontaneous abortion (RR = 1.59, 95% CI: 1.04-2.45, RR = 2.04, 95% CI: 1.28-3.24).

CONCLUSIONS

In conclusion, the likelihood of an elevated risk of spontaneous abortion caused by HPV vaccination during the periconceptional or gestational period could not be completely ruled out. Given the lack of evidence, further research is needed to examine the effect of HPV vaccination on spontaneous abortion.

Frequency and Risk Factors Associated with Prematurity: A Cohort Study in a Neonatal Intensive Care Unit

Background/Objectives: Prematurity rates remain high and represent a challenge for the public health systems of any country, with a high impact on neonatal mortality. This study aimed to evaluate the frequency and environmental and maternal-fetal risk factors for premature birth in a cohort of parturient women, with their newborns monitored in a neonatal intensive care unit at a private reference hospital. Methods: A cohort was carried out between 2013 and 2018 among parturient women living in a capital city in the Northeast of Brazil whose newborns were admitted to the neonatal intensive care unit. This study was approved by the Research Ethics Committee of the University of Fortaleza. The information collected comprised data from both medical records and hydrosanitary data from maternal homes. Results: The prevalence of prematurity among live births (n = 9778) between 2013 and 2018 at this hospital was 23%. The frequency of prematurity among those eligible (n = 480) was 76.9%, and the frequency of eligible premature babies (n = 369) in relation to the total number of births in this period was 3.8%. In the multivariate analysis, the significant risk factors for prematurity were primigravida (RR = 1.104, 95%CI: 1.004-1.213) and hypertensive syndromes during pregnancy (RR = 1.262, 95%CI: 1.161-1.371), and the significant protective factor was the highest number of prenatal consultations (RR = 0.924, 95%CI: 0.901-0.947). Conclusions: This study contributes to providing greater visibility to prenatal care and the understanding of complications during pregnancy and childbirth care. These results indicate the need to implement public policies that promote improvements in the population's living conditions and care for pregnant women to reduce premature births and, consequently, neonatal and infant mortality.

Association between Human Papillomavirus 16 Viral Load in Pregnancy and Preterm Birth

Recent evidence shows increased preterm birth risk with human papillomavirus-16 (HPV16) infection during pregnancy. This study aimed to measure the association between HPV16 viral load during pregnancy and preterm birth. We used data from participants in the HERITAGE study. The Linear Array assay was used for HPV DNA testing on vaginal samples collected during the first and third trimesters of pregnancy. The HPV16 viral load was measured with a real-time polymerase chain reaction. We used logistic regression to measure the associations between HPV16 viral load during pregnancy and preterm birth (defined as birth before 37 weeks of gestation). The adjusted odd ratios (aORs) and the 95% confidence intervals [CIs] were estimated with inverse probability treatment weighting of the propensity score. This study included 48 participants who tested positive for HPV16 during the first trimester of pregnancy. The aOR for the association between first-trimester HPV16 viral load (higher viral load categorized with a cutoff of 0.5 copy/cell) was 13.04 [95% CI: 1.58-107.57]). Similar associations were found using different cutoffs for the categorization of viral load during the first and third trimesters. Our findings suggest a strong association between a high HPV16 viral load during pregnancy and preterm birth, demonstrating a biological gradient that reinforces the biological plausibility of a causal association.

Spontaneous preterm birth risk among HPV-vaccinated and -unvaccinated women: a nationwide retrospective cohort study of over 240 000 singleton births

OBJECTIVE

To determine whether prior human papillomavirus (HPV) vaccination contributes to preterm birth risk.

DESIGN

Population-based retrospective cohort study.

SETTING

Denmark.

POPULATION

A cohort of 243 136 primiparous females born in the period 1961-2004 who had a singleton delivery at >22 weeks of gestation occurring from October 2006 to December 2018.

METHODS

High-quality nationwide registries were linked to provide information on demographics, birth outcomes, HPV vaccination status, smoking, body mass index (BMI), and cervical lesions and treatment history.

MAIN OUTCOME MEASURES

We assessed the association between HPV vaccination status and spontaneous preterm birth using logistic regression. To address age at vaccination, we performed a stratified analysis by vaccination before and after 17 years of age.

RESULTS

In age-adjusted and fully adjusted models, there was a nonsignificant difference in the odds of spontaneous preterm birth between vaccinated and unvaccinated women (OR 1.05 (95% CI 0.99-1.12) and OR 1.04 (95% CI 0.98-1.10), respectively). There was no difference in the odds of spontaneous preterm birth in relation to time between vaccination and pregnancy. In contrast, compared with unvaccinated women, the odds of preterm birth were lower among women vaccinated before the age of 17 years (fully adjusted OR 0.87, 95% CI 0.75-1.00). This association was not present for women vaccinated at ≥17 years of age.

CONCLUSIONS

In this large, population-based cohort, we found reduced odds of spontaneous preterm birth among women vaccinated against HPV at an early age compared with women who were unvaccinated. It seems conceivable that HPV vaccination may not only reduce the incidence of cervical cancer and severe precursors, but also reduce the risk of preterm birth related to HPV infection.

The impact of HPV vaccination beyond cancer prevention: effect on pregnancy outcomes

While the benefits of human papillomavirus (HPV) vaccination relating to cervical cancer prevention have been widely documented, recent published evidence is suggestive of an impact on adverse pregnancy outcomes (APOs) in vaccinated mothers and their infants, including a reduction in rates of preterm births and small for gestational age infants. In this review, we examine this evidence and the possible mechanisms by which HPV vaccination may prevent these APOs. Large-scale studies linking HPV vaccination status with birth registries are needed to confirm these results. Potential confounding factors to consider in future analyses include other risk factors for APOs, and historical changes in both the management of cervical precancerous lesions and prevention of APOs. If confirmed, these additional benefits of HPV vaccination in reducing APO rates will be of global significance, due to the substantial health, social and economic costs associated with APOs, strengthening the case for worldwide HPV immunization.

Eliminating Cervical Cancer: Progress and Challenges for High-income Countries

In 2020, the World Health Organization launched a major initiative to eliminate cervical cancer globally. The initiative is built around the three key pillars of human papillomavirus (HPV) vaccination, cervical screening and treatment, with associated intervention targets for the year 2030. The '90-70-90' targets specify that 90% of adolescent girls receive prophylactic HPV vaccination, 70% of adult women receive a minimum twice-in-a-lifetime cervical HPV test and 90% receive appropriate treatment for preinvasive or invasive disease. Modelling has shown that if these targets are met, the elimination of cervical cancer, defined as fewer than four cases per 100 000 women per annum, will be achieved within a century. Many high-income countries are well positioned to eliminate cervical cancer within the coming decades, but few have achieved '90-70-90' and many challenges must still be addressed to deliver these critical interventions effectively. This review considers the current status of cervical cancer control in relation to each of the three elimination pillars in high-income countries and discusses some of the developments that will assist countries in reaching these ambitious targets by 2030.

Has the human papillomavirus (HPV) immunization programme improved obstetric outcomes in spontaneous delivery? An ecological study

OBJECTIVE

To measure the rates of adverse obstetric outcomes in spontaneous delivery in a population of young women with high uptake of the bivalent human papillomavirus (HPV) vaccine.

STUDY DESIGN

This was a population-based ecological study with data from the Aberdeen Maternity and Neonatal Databank, UK. All women born between 1986-1996 with spontaneous singleton live birth at age 20-30 years were included for analysis. Exposure was defined according to maternal year of birth and HPV immunisation eligibility: pre-immunisation cohort (1986-1990), catch-up immunisation cohort (1991-1994) and routine immunisation cohort (1995-1996). Outcomes were defined as spontaneous preterm birth (PTB), low birth weight (LBW) and pre-labour preterm rupture of membranes (pPROM). Generalized estimating equation models were applied, adjusted for deprivation, smoking status, marital status, body mass index, parity, maternal age and year of infant delivery.

RESULTS

A total of 6515 spontaneous singleton live births were included in final analysis, with 5134 births included in the pre-immunisation cohort, 1250 in the catch-up immunisation cohort and 131 in the routine immunisation cohort. Compared with the pre-immunisation cohort, no statistically significant reduction on PTB, LBW or pPROM were observed in either immunised cohorts. The adjusted odds ratio (aOR) on PTB was 0.64 (95 % confidence interval, 0.40-1.03) in the catch-up cohort and 0.71 (0.28-1.77) in the routine cohort. The corresponding aOR were 0.88 (0.54-1.45) and 0.51 (0.16-1.62) for LBW and 1.62 (0.58-4.54) and 1.51 (0.21-11.01) for pPROM.

CONCLUSIONS

We did not observe a significant reduction on PTB, LBW or pPROM among spontaneous singleton live birth in either HPV immunised cohorts, although the additional benefit in improving obstetric outcomes cannot be excluded because of the limits of the sample size and the study design. Further demonstration is warranted when more women in the fully HPV immunised cohorts embark on pregnancy.