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Abstract

Background:

Starting vaccination in pregnant women; numerous theories have been proposed that the vaccine might affect the mother or the fetus.

Objective:

The goal of this research was to see whether there was a link between the Sinopharm vaccination and certain pregnancy outcomes in COVID-19-vaccinated women.

Study design:

This is a retrospective cohort study.

Method:

This study was conducted on pregnant women who delivered from 1 August 2021 to 1 January 2022 in Yazd city. We have followed the STROBE Guidelines when preparing the manuscript. In this period time, all pregnant women were 5787 people in which 5666 were in the second and third trimester. Among these women, 1222 women were randomly selected.

Results:

Among 1222 pregnant women, 558 (45.6%) women had received one dose vaccine, 162 (13.3%) people had received two doses, and 502 (41.1%) women had not been vaccinated. On crude analysis, there was no significant difference between vaccinated and non-vaccinated groups. After adjusting for maternal age, maternal body mass index, parity, stillbirth history, abortion history, and gestational diabetes in multivariate analysis, no differences were found between the groups in pregnancy as well.

Conclusion:

Vaccinations during pregnancy seem to have no negative effects on the mother or the baby. This finding may aid pregnant women in deciding whether or not to take the vaccination.

Keywords

COVID-19 vaccines pandemic pregnant women safety

Introduction

Pregnant women are one of the vulnerable groups to some health consequences for which special care is considered so that they can give birth to a healthy baby. However, these women may sustain injuries during pregnancy or delivery. Conditions such as elderly to advanced maternal age, underlying disorders such as diabetes or hypertension, poor level of education, history of miscarriage or stillbirth may affect both the mother and the baby during pregnancy.^1,2 Injuries to the fetus can range from underweight and weight loss at birth, preterm birth to a variety of birth defects, stillbirths, and abortion.

Studies have shown that pregnant persons were at greater risk of severe COVID-19 infection, hospitalization at intensive care units, invasive ventilation services, and death than non-pregnant women with the Delta variant; however, the need for intensive care unit (ICU) and invasive ventilation services increased as well.³ COVID-19 vaccinations were developed after a difficult time during the epidemic.⁴ Although practically all nations now had access to COVID-19 vaccines, vaccine apprehension was a new issue; some people feared the vaccines may produce serious side effects.⁵ Pregnant women are one of the priority groups that received the vaccine,⁶ but the acceptance of vaccine is low, most common refusal reason is the probability of harm to the fetus,⁷ but all vaccines are used in second or third trimester, which prevents the probable adverse reaction.⁸ Starting vaccination in pregnant women, various hypotheses were made that the vaccine might harm the mother or fetus, including the effect of vaccination on stillbirth, abortion, or premature birth in these people, but various studies performed on these cases show that there was no significant relationship. The association between vaccination and some outcomes such as low Apgar score, stillbirth, preterm birth, and small for gestational age were discussed in several studies, in which there was no significant association.^9
–12

This study aimed to look at vaccination and its relationship with outcomes like Apgar score, preterm delivery, and birth weight. In the modeling, factors including maternal age, maternal body mass index (BMI), parity, stillbirth history, abortion history, and gestational diabetes were included as confounders.

Materials and methods

Data accessing and variable selection

Pregnant women surveillance systems in Iran registered demographic and anthropometry information of pregnant women and some other factors such as gestational diabetes mellitus and congenital malformation.¹³ Neonatal data are recorded after birth, including Apgar score, weight, height, head circumference, small for gestational age, and congenital deformity. In Iran, all pregnant women are given the Sinopharm vaccination to protect them against COVID-19. We have followed the STROBE Guidelines when preparing the manuscript.

Study design and sample size

This retrospective cohort study was conducted on pregnant women who delivered during 1 August 2021 to 1 January 2022 in Yazd city. In this period, there were 5787 pregnant women, of which 5666 were in the second and third trimesters. Among these women, 1222 (sample size was estimated in formula (1)) women were randomly selected (Figure 1)

n = \frac{{(Z_{1 - \frac{α}{2}} . \sqrt{(r + 1) P (1 - P)} + Z_{1 - β} . \sqrt{r P_{1} (1 - P_{1}) + P_{2} (1 - P_{2})})}^{2}}{r {(P_{2} - P_{1})}^{2}}

(1)

where α = 0.05; β = 0.2; proportion in group 1: 0.4; proportion in group 2: 0.9; ratio (group 2/group 1): 1

P = (P_{1} + P_{2}) / (1 + r)

Figure 1.

Study flow diagram to develop historical cohort study.

Statistical analysis

Analysis of variance (ANOVA) and chi-square tests were used to compare between vaccine statuses (non-vaccine/one dose/two doses). Multivariate logistic regression was conducted to predict the impact of vaccine status (One dose vs none, two doses vs none, and two doses vs one) on delivery outcomes (preterm delivery, low birth weight, small for gestational age (birth weight < 10th percentile for gestational age, Apgar < 6 at 5 min, in this model, maternal age, maternal BMI, parity, stillbirth history, abortion history, and gestational diabetes) were considered as confounders. All statistical analyses were done in STATA version 12.

Results

Among 1222 pregnant women, 558 people had received one dose vaccine, 162 people had received two doses, and the rest had not been vaccinated. When vaccinated pregnant ladies were compared to unvaccinated pregnant women, it was shown that the vaccinated women were somewhat older. There were no statistically significant differences in any maternal factors. Gestational diabetes mellitus and parity were considered pregnancy characteristics in which two characteristics were not significantly different in understudy women. Comparing delivery and post-partum characteristics was a major subject of this study; to this subject, preterm delivery, Apgar score, and cesarean delivery were examined. There is no statistically significant difference.

Birth weight, birth height, and congenital malformation were three variables as newborn characteristics; all three variables were not statistically significant differences in vaccinated and non-vaccinated mothers. Table 1 presents more detail.

Table 1.

Comparison maternal background, pregnancy, delivery, and post-partum characteristics, and newborn characteristics by vaccination status.

	UnvaccinatedN = 502 (41.1%)	One dosen = 558 (45.7%)	Two dosen = 162 (13.2)	P
Maternal background characteristics
Maternal age (mean ± SD)	29.3 ± 5.9	29.7 ± 6.1	30.1 ± 5.9	0.22
Obesity (30 < BMI)	167 (33.6)	193 (35.3)	68 (42)	0.24
Stillbirth history	1 (0.2)	2 (0.4)	0 (0)	0.7
Abortion history	80 (15.9)	88 (15.8)	35 (21.6)	0.2
Pregnancy characteristics
Gestational diabetes mellitus	99 (19.7)	120 (21.5)	47 (29)	0.1
3 < Parity	27 (5.4)	28 (5)	6 (3.7)	0.7
Delivery and post-partum characteristics
Preterm birth	36 (7.2)	37 (6.6)	7 (4.3)	0.22
Apgar < 6 at 5 min	3 (0.6)	3 (0.5)	0 (0)	0.92
Cesarean delivery	243 (48.4)	256 (45.9)	75 (46.3)	0.7
Newborn characteristics
Birth weight(mean ± SD)	3078.2 ± 487.8	3196.2 ± 1538.3	3105.3 ± 414.6	0.34
Birth height (mean ± SD)	49.7 ± 3.1	50 ± 2.6	50.1 ± 2.2	0.3
Head circumference(mean ± SD)	34.4 ± 2.2	34.5 ± 1.9	34.4 ± 1.4	0.87
Congenital malformation	1 (0.2)	0 (0)	0 (0)	0.48

SD: standard deviation; BMI: body mass index.

The result of multivariate analysis is show in Table 2. This analysis was conducted by adjusting for maternal age, maternal BMI, parity, stillbirth history, abortion history, and gestational diabetes. Any association was not founded between vaccination status and these variables.

Table 2.

Result of multivariable modeling in vaccination status.

Outcomes^a	One dose vs none		Two doses vs none		Two vs one dose
Outcomes^a	RR (95% CI)	P	RR (95% CI)	P	RR (95% CI)	P
Preterm birth	0.94 (0.60–1.47)	0.79	0.60 (0.28–1.33)	0.22	0.63 (0.29–1.41)	0.26
Low birth weight (<2500 g)	0.68 (0.45–1.05)	0.09	0.68 (0.35–1.31)	0.25	0.95 (0.47–1.88)	0.89
Small for gestational age	0.83 (0.56–1.24)	0.37	0.58 (0.29–1.16)	0.45	0.94 (0.35–1.07)	0.91
Apgar < 6 at 5 min	0.87 (0.17–4.3)	0.88	1 (–)	—	1 (–)	—

CI: confidence interval; RR: relative risk.

Adjusted by maternal age, maternal BMI, parity, stillbirth history, abortion history, gestational diabetes.

Discussion

This study’s results showed that there was no significant relationship between receiving a vaccination and increased risk of stillbirth, abortion, congenital heart defects, risk of preterm delivery, low birth weight, and decreased Apgar score.

The first factor to be assessed was the association between vaccination during pregnancy and the likelihood of preterm birth. Out of a total of 80 births occurred, only seven were related to women who received two doses of the vaccine during pregnancy, and in people receiving a dose of vaccine or did not receive the vaccine, the ratio of preterm births was almost equal; these results were repeated in another study, and it seems that vaccination cannot increase the risk of preterm birth.¹⁴

Low birth weight is one of the consequences that can be affected by various risk factors during pregnancy. The incidence of LBW was lower in people who were vaccinated than in those who were not vaccinated, although this difference was not statistically significant, a study in Israel also showed that the mean weight of infants born to vaccinated mothers was not significantly different from those who were not vaccinated.¹⁵

One of the consequences that can occur after pregnancy for a baby is small for gestational age, and several factors can influence this outcome. Vaccination during pregnancy was one of the factors that increased the hypothesis of its association with an increased likelihood of this outcome, and there is no significant relationship; the results showed that mothers who received the vaccine could experience an even lower incidence of small for gestational age. A US study of pregnant women found that vaccination had no effect on small for gestational age.¹⁴

Apgar score in the first 5 min is one of the indicators that indicate the health status of baby, some factors may reduce the score of these people during pregnancy, the concern was the effect of vaccination on reducing the Apgar score, this study’s results showed that there was no significant change in the Apgar score of infants whose mothers received the vaccine during pregnancy, which was similar to another study conducted in Israel.¹⁵

The COVID-19 pandemic had several effects on different populations, and pregnant mothers were one of the groups affected by the pandemic. Missed prenatal care, pregnancy weight gain, and stress were all shown to have a deleterious impact on the baby, reducing the effectiveness of immunization. Any type of vaccination that is given at the public level can have short-term side effects,¹⁶ but in the modeling conducted in the present study, it was shown that COVID-19 vaccination during pregnancy, in which confounding factors were applied, would not cause any side effects to the mother as well as the fetus.

Limitation

There are some limitations in this study; first, Sinopharm vaccine was assessed because just this vaccine is injected for pregnant women in Iran, another limitation was the unknown COVID-19 infected pregnant women, and these data were not accessible. And, this study assessed just fetus and neonatal outcomes in second and third trimesters, some adverse reactions may be accrued in first trimester.

Conclusion

Vaccinations during pregnancy seem to have no negative effects on the mother or the baby. This finding may aid pregnant women in deciding whether or not to take the vaccination. However, it’s recommended to design a prospective cohort study to find long time adverse reaction.

Supplemental Material

sj-docx-1-whe-10.1177_17455057231189554 – Supplemental material for COVID-19 vaccine in pregnant women and pregnancy outcomes: A historical cohort in center of Iran

Supplemental material, sj-docx-1-whe-10.1177_17455057231189554 for COVID-19 vaccine in pregnant women and pregnancy outcomes: A historical cohort in center of Iran by Mahdi Zare Sakhvidi, Mohammad Hassan Lotfi, Hossein Fallahzadeh, Saeed Hosseini, Forouzandeh Kalantari and Moslem Taheri Soodejani in Women’s Health

Footnotes

Acknowledgements

None.

Declarations

ORCID iD

Moslem Taheri Soodejani

Supplemental material

Supplemental material for this article is available online.

Implications for practice

Not applicable.

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Supplementary Material

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