Impact Of Influenza Virus Infection In Pregnant Women On Pregnancy Outcome During Influenza Pandemic

Objectives:Influenza A or B virus infection during pregnancy may affect pregnancy outcomes for both the mothers and their offspring. The study had two aims, a) to investigate risk factors of influenza virus infection during pregnancy, and b) to analyze the impact of influenza virus infection on pregnancy and offspring outcomes.Method:Part Ⅰ: We searched in Pub Med, MEDLINE, Embase, Google Scholar, and Wang Fang Database using Me SH terms or the keywords as “pregnancy”, “gravidity”, “pregnant women”, “mother”, “maternal” and/or “neonatal”, “embryo”, “fetus” and “influenza”, “influenza virus” from January 1, 1989 to November 15, 2015. Thirteen articles that were clinical studies comparing between pregnant women with influenza A or B virus infection and those without infection were included. There are 8,927 patients of pregnant women in study group and 489,422 pregnant women as control group in this meta-analysis. The included articles were read carefully and judged using the Newcastle-Ottawa Scale(NOS) standards. Risk factors for influenza A or B virus infection during pregnancy and the consequences of these infections on pregnancy outcomes of both mothers and their offspring were analyzed by Review Manager Version 5.0(Rev-Man 5.0). Part Ⅱ: Then, for further searching the cases with influenza virus infection in Guangzhou, China, pregnant women who were hospitalized and had parturition in the first Affiliated Hospital of Jinan University from October to December of 2009 were selected to this retrospective observational clinical study. Thirty-five pregnant women who were suspected influenza virus infection during pregnancy were included to study group. There were 639 pregnant women without influenza virus infection during pregnancy as control group. The data such as basic information, clinical diagnosis, biochemical and serological assay findings from the mothers, ultrasound measure parameters of fetuses, parameters of their newborns at delivery, e.g. birth weight, birth height, and so on were collected. Data was analyzed by SPSS19.0. T-test was used to analyze measurement data. Chi-square test and logistic regression was used to analyze enumeration data.Result:Part Ⅰ: After carefully search,thirteen articles were confirmed the relative risks or negative effects of pregnant women with influenza virus infection. Data was extracted and analyzed by the software. It was shown that pregnant women with preexisting diabetes mellitus(P<0.00001, RR=2.83, 95% CI: 2.44~3.28), obesity(P<0.00001, RR=1.30, 95% CI: 1.21~1.39) and asthma(P<0.00001, RR=1.94, 95% CI: 1.65~2.28) had higher incident rates of influenza virus infection. Mothers with influenza virus infection had a higher incident rate of stillbirth(P=0.03, RR=2.53, 95% CI: 1.08~5.94), their offspring had low 5-minute Apgar scores(P=0.01, RR=1.36, 95% CI: 1.07~1.73). The other factors such as smoking, hypertension and anemia were not shown as increased risk for getting influenza virus infection during pregnancy. Influenza virus infection during pregnancy didn’t affect the choice of delivery modes. Influenza virus infection during pregnancy was not at increased risk for preterm labor, low birth weight and small for gestational age babies. PartⅡ: The clinical study was shown that pregnant women with the first gravidity are easier to get influenza virus infection(P=0.041,OR=0.604,95% CI:0.367~0.992) compared to those with two or more gravidities. Pregnant women suspected with influenza virus infection had more chances for placental and/or amniotic diseases, such as functional placenta(X2=8.224,P=0.004,OR=38.667,95% CI:3.418~437.379), placental calcification(X2=7.853,P=0.005,OR=7.685,95% CI:1.437~41.100), amnionitics(X2=8.310, P=0.004, OR=39.576, 95% CI : 3.499 ~ 447.650) and polyhydramnios/increased amniotic fluid(P=0.040,OR=2.555,95% CI:1.012~6.449) compared with normal pregnant women.Conclusion:Part Ⅰ: Preexisting diabetes, asthma and obesity before pregnancy are risk factors for influenza A or B virus infection during pregnancy. Pregnant women with influenza virus infection have an increased risk for stillbirth, and their offspring have lower five-minute Apgar scores postpartum. PartⅡ: This clinical study was shown that pregnant women of the first gravidity might have higher risk for getting suspected infection with influenza virus during pregnancy than those of grand multi-gravidity and/or multi-parity. Pregnant women suspected with influenza virus infection during pregnancy might have more chance of low functional placenta, placental calcification, amnionitics and polyhydramnios.