Analysis of maternal and infant perinatal period outcomes of pregnant women with premature birth caused by hypertensive disorder complicating pregnancy

Abstract

Objective To study the maternal and infant perinatal period outcomes of pregnant women with premature birth caused by hypertensive disorder complicating pregnancy. Methods From January 1, 2015 to December 31, 2016, a total of 87 cases of singleton pregnancy with premature birth caused by hypertensive disorder complicating pregnancy were selected as research subjects and were included into study group. The gestational age ranged from 28 weeks to 36+ 6 weeks. Among those 87 pregnant women, 73 cases were complicated with preeclampsia (PE) including mild PE (9 cases), severe PE (60 cases), and chronic hypertension complicated with PE (4 cases), and 14 cases were not complicated with PE including gestational hypertension(10 cases) and chronic hypertension (4 cases). Meanwhile, another 120 cases of singleton pregnancy of spontaneous preterm and preterm premature rupture of membranes with premature birth with the same gestational weeks during the same period and in the same hospital were selected as control group. The clinical data of all subjects were analyzed by retrospective method. The differences of general maternal characteristics, pregnancy and preterm infants′ outcomes, as well as birth weights, Z scores of birth weights of preterm infants in different gestational age periods were statistically analyzed. Gestational age at admission and gestational age at delivery were analyzed by independent-samples t test between two groups. Age and pre-pregnancy body mass index (BMI) were analyzed by Wilcoxon rank sum test. The constituent ratio of delivery mode (vaginal delivery and cesarean section), prenatal antimicrobial drug use rate of pregnant women, incidence of hyperbilirubinemia, pneumonia and gastrointestinal disorders of premature infants were compared by chi-square test, continuity correction chi-square test or Fisher exact probability method. This study met the requirements of the World Medical Association Declaration of Helsinki revised in 2013. Results ①There were no significant differences between two groups in age, gestational age at admission, gestational age at delivery, and the constituent ratio of delivery modes (P>0.05). ②Before pregnancy, the BMI of pregnant women in study group was 23.5 kg/m2 (21.1-27.7 kg/m2), which was significantly higher than that of 22.4 kg/m2 (20.3-24.6 kg/m2) in control group. And the difference between two groups was statistically significant (Z=-3.480, P=0.001). ③Comparison of the constituent ratio of delivery modes between two groups showed statistically significant difference (χ2=124.130, P<0.001). The prenatal antimicrobial drug use rate of pregnant women in study group was 10.3% (9/87), which was significantly lower than that of 24.2% (29/120) in control group, and there was a statistically significant difference (χ2=6.429, P=0.011). ④The birth weight of preterm infants in study group was 2 250.0 g (1 820.0-2 600.0 g), which was significantly lower than that of 2 650.0 g (2 212.5-2 980.0 g) in control group, and the difference was statistically significant (Z=-3.866, P<0.001); and the Z score of birth weight of preterm infants in study group was -0.63 (-1.27-0.10), which was significantly lower than that of 0.33 (-3.38-0.85) in control group, and the difference was also statistically significant (Z=-5.695, P<0.001). In addition, the birth weight and Z score of birth weight of preterm infants with gestational age ≥32-34+ 6 weeks and gestational age ≥ 34-36+ 6 weeks in study group were lower than those in control group, and all the differences between 2 groups were also statistically significant (preterm infants with gestational age ≥ 32-34 weeks: Z=4.706, -3.690, P<0.001; preterm infants with gestational age ≥ 34-3636 weeks: Z=-5.116, -5.555, P<0.001). ⑤ The proportion of 1 min Apgar score ≤7 scores after birth, incidence of neonatal asphyxia, and incidence of mild asphyxia in study group were 12.6% (11/87), 12.6% (11/87), and 9.2% (8/87), respectively, which were higher than those in control group 3.3% (4/120), 3.3% (4/120), and 3.3% (4/120), respectively, and all the differences were statistically significant (χ2= 6.504, 9.017, 7.514; P= 0.011, 0.003, 0.025). ⑥ In study group, there were statistically significant differences in the constituent ratio of the delivery modes and rate of preterm infants transferred to the neonatology department between pregnant women complicated with PE and uncomplicated with PE (P=0.002; χ2=4.351, P=0.037). Conclusions Reasonable diet and weight control before pregnancy are of great significance to prevent the occurrence and development of hypertensive disorder complicating pregnancy. Premature birth caused by hypertensive disorder complicating pregnancy can increase the risk of neonatal asphyxia. More closely monitored and actively intervened measures should be conducted on pregnant women with hypertensive disorder complicating pregnancy, so as to decrease the incidence of premature birth. Key words: Hypertension, pregnancy-induced; Pre-eclampsia; Premature birth; Pregnancy outcome; Infant, premature; Asphyxia neonatorum; Pregnant women