Design and settings
We used a retrospective case-crossover design. Each subject’s data is treated as if they were from a matched pair, switching between periods of different risk (pre-pandemic vs. pandemic period) [15, 16]. The study was conducted with pregnant women from the Tzotzil ethnic group, residents of Chiapas, Mexico. Between June and December 2021, women who had experienced a pregnancy both before and during the COVID-19 pandemic were invited to be volunteer participants.
Pilot
Eighteen women in the study population were pilot-tested with the questionnaire. As a result of the pilot test, three questions were modified. The supplementary material contains the final instrument.
To estimate the sample size, we applied the case-control study design formula, using one control for each case. This approach was appropriate because our retrospective case-crossover study utilized a previous pandemic pregnancy as a control measure considering that each participant served both as a case and as a control. The sample size calculation was based on the following parameters: a control exposure frequency of 50%, an odds ratio (OR) of 2.5 to detect the minimum risk, a significance level of 0.05, and a test power of 0.80. As a result, we determined that a total sample size of 40 cases was needed [17, 18].
Standardized personnel administered a questionnaire during one of their visits to one of two health centers where we had permission to conduct the study in San Cristobal de las Casas, Mexico. Both health centers belonged to state services of the Mexican Ministry of Health. One center provided first-level care, and the other provided second-level care. The questionnaire was administered in a private room provided by the authorities of these health centers and was conducted entirely in Spanish. The questionnaire was not translated into Tzotzil (the most spoken indigenous language in the San Cristóbal de las Casas community); however, a translator proficient in both Spanish and Tzotzil was available during the data collection process.
Participants were asked to provide information about their antenatal care utilization during their previous and current pregnancy. They were also asked several questions to determine their perception of COVID-related risks and fear of contagion during their most recent pregnancy, which occurred during the pandemic.
Informed consent
was obtained verbally, during which participants were provided detailed information about the study’s objectives and the procedures they were required to follow. It was emphasized that participation was entirely voluntary and that they had the freedom to withdraw at any time without consequences. Subsequently, when participants lacked literacy skills, the designated administrator presented the questionnaire orally, and at least one literate witness signed the informed consent form.
Inclusion criteria
Participants included in this cross-over study were: (1) Women with recurrent pregnancy, whose previous pregnancy occurred up to three years before the health contingency and the current or most recent pregnancy during the COVID-19 pandemic, (2) Attending San Cristóbal de las Casas health centers for antenatal care, and (3) Agreed to participate in the study voluntarily and signed the informed consent when the participant was literacy, when the woman wanted to participate but was illiteracy, informed consent was obtained orally and one literate witness signed the informed consent form.
Exclusion criteria
Women were excluded if they were unable to respond to the questionnaire or interview because of a mental or cognitive apparent disability.
Risk perception
We evaluated two components from the Health Belief Model: perceived susceptibility and severity. The items that made up both scales resulted from a discussion among the group of researchers based on the definition of both constructs. As Conner and Norman have pointed out “The HBM had the advantage of specifying a discrete set of common-sense beliefs”. [19] Based on the characteristics of the study population, we opted for items expressed in the simplest and most parsimonious way. The susceptibility component was evaluated with three questions: (1) I could get COVID by going to pregnancy checkups, (2) People around me do not follow the COVID safety protocol, and (3) My baby could get COVID if I go to pregnancy checkups; a likert scale format was used with four response options: (1) It is something I’m concerned about, (2) No, it doesn’t concern me, (3) It’s not something I had thought about, (4) I really don’t think it could happen.
The severity component was assessed with four questions: (1) Illness from COVID-19 is more likely to be more aggressive for someone like me, (2) It would be more difficult for me to recuperate from COVID-19 than for the general population, (3) I could have premature labor due to COVID-19, and (4) I could have an abortion due to COVID-19. A Likert scale format was used with 6 response options to each question: (1) strongly disagree, (2) disagree, (3) kind of disagree, (4) kind of agree, (5) agree, and (6) strongly agree.
In order to determine the total susceptibility variable, a value of zero was assigned to each of the three susceptibility questions if the response score was 2 (No, it doesn’t concern me) or higher. If the response selected was 1 (It is something I’m concerned about), the value of one was assigned. These values were then added together to obtain the total susceptibility score. To calculate the total severity variable, each of the four severity questions was assigned a value of one if the response was 4 (kind of agree) or higher, and a value of zero if it was lower. These variables were then added together to obtain the total risk score.
Fear of contagion
Fear was evaluated with the question: Were you afraid of getting infected? (Were you afraid of catching it? ) which could be answered with yes or no.
Antenatal care utilization
To consider the antenatal care utilization as adequate a minimum of six visits was required, while attending less than that number was considered inadequate. Based on the Mexican Official Regulation called “NOM-007-SSA2-2016, for the Care of Women during Pregnancy, Childbirth, and Puerperium, and of the Newborn”, it is recommended that pregnant women with low risk attend 8 antenatal care visits and a minimum of 5 visits [20]. However, to prevent the spread of SARS-CoV-2, it was recommended that the frequency of check-ups be spaced out and the number of patients reduced by day, thus reducing the recommended antenatal care visits from 8 to 6 [21].
Ethical considerations
The Ethics and Research Committee of the Faculty of Medicine of the National Autonomous University of Mexico approved the protocol of the present study under Research Protocol: FM/DI/115/2019. Participation in this study was voluntary. Before completion, participants were informed of their rights as outlined in the Helsinki Declaration. [22] All participants were informed about the study’s objective, their research rights, that there would be no consequences if they chose not to participate, and the confidential nature of their participation. When a woman was illiterate but wanted to participate, informed consent was obtained orally, and one literate witness signed the informed consent form.
Statistical analysis
The analysis considered data from the questionnaire regarding sociodemographic information, antenatal care utilization, as well as perceptions of severity, susceptibility, and fear of contagion. We described categorical variables expressed as numbers and percentages (%), and Chi-square tests were used to test differences between the groups of data before and during the pandemic. A p-value of less than 0.05 was considered significant.
To test the concordance between vulnerability and severity items, Gamma and Kendall’s coefficients were applied to the whole sample based on the ordinal nature of each item (Likert scale from 1 to 5).
Using a logistic regression model, we evaluated the changes in the utilization of antenatal care before and during the pandemic. Afterward, additional adjusted logistic regression models were employed to estimate the association between adequate antenatal care utilization and severity and susceptibility indices. Variables with a p-value of less than 0.20 in the bivariate analyses were used to adjust the model. Goodness-of-fit analysis was performed with the Hosmer-Lemeshow test. The data were analyzed with Stata v. 18. (Stata Corp, College Station, Texas, USA).
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