Risk Factors of Birth Asphyxia in Pregnancy 37 Complete Weeks and Over by Apgar Score Less Than 7 at 5 Minutes

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Thai Journal of Obstetrics and Gynaecology April 2010, Vol. 18, pp OBSTETRICS Risk Factors of Birth Asphyxia in Pregnancy 37 Complete Weeks and Over by Apgar Score Less Than 7 at 5 Minutes Surangtip
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Thai Journal of Obstetrics and Gynaecology April 2010, Vol. 18, pp OBSTETRICS Risk Factors of Birth Asphyxia in Pregnancy 37 Complete Weeks and Over by Apgar Score Less Than 7 at 5 Minutes Surangtip Thangwijitra MD, Chamnan Sripramodya MD, Sukawadee Kanchanawat MD. Department of Obstetrics and Gynecology, Rajavithi Hospital, Bangkok 10400, Thailand ABSTRACT Objectives: To identify risk factors of birth asphyxia determine by Apgar score 7 at 5 minutes in pregnant women delivered at 37 weeks of gestation. Materials and Methods: Medical records of pregnant women with gestational age 37 weeks delivered at Rajavithi Hospital between January 1, June 30,2005 were reviewed. A total number of cases was 130 pregnancies with neonatal Apgar score 7 at 5 minutes and 260 pregnancies with neonatal Apgar score 7 at 5 minutes during that period were chosen for controls. Risk factors were analyzed by univariate and multiple regression analysis. Results: Risk factors that significantly associated with birth asphyxia in pregnancy 37 weeks were: small for gestational age(sga) (OR=12.72;95%CI ,p 0.001), prolonged PROM (OR=8.72;95%CI ,p=0.028), narcotic analgesic used (OR=6.78;95%CI ,p=0.023), no antenatal care (OR=5.87;95%CI ,p=0.008), vaginal breech delivery (OR=5.64;95%CI ,p=0.028), advance maternal age (OR=4.76;95%CI ,p 0.001), large for gestational age (LGA) (OR=3.95;95%CI ,p=0.037), cord compression (OR=3.78;95%CI ,p=0.048), oxytocin usage (OR=3.50;95%CI ,p=0.027) and meconium-stain amniotic fluid (OR=3.16;95%CI ,p=0.018). Conclusion: Risk factors significantly associated with birth asphyxia in pregnancy 37 weeks were SGA, prolonged PROM, narcotic analgesic used, no antenatal care, vaginal breech delivery, elderly maternal age, LGA, cord compression, oxytocin usage and meconium-stain amniotic fluid. Keywords: Apgar score, birth asphyxia Introduction The Ninth National Health Development Plan ( ) provided the goal of building healthy conditions for all Thai citizens in a holistic manner in partnership with all sectors concerned. One of mother and child health care goal is the rate of birth asphyxia by Apgar score 7 at 1 minute less than 30:1,000 livebirths. Department of Obstetrics and Gynecology, Rajavithi Hospital has responded to the policy by improving the standard of maternal and neonatal care. 54 Thai J Obstet Gynaecol From , birth asphyxia uses Apgar score 7 at 1 minute. However it demonstrated poor sensitivity as a marker of birth asphyxia (1). The more effective diagnosis for birth asphyxia is needed. The American College of Obstetricians and Gynecologists (1998 and 2004) recommended the birth asphyxia as the following statements: profound metabolic or mixed acidemia (ph 7.0) determined on an umbilical cord arterial blood sample, persistent Apgar score of 0 3 for longer than 5 minutes,evidence of neonatal neurological sequelae such as seizures, coma, or hypotonia; or dysfunction of one or more of the following systems : cardiovascular, gastrointestinal, hematological, pulmonary, or renal. (2) As a result, Apgar score at 5 minutes 7 is potentially indicated birth asphyxia. This study was aimed to determine the risk factors of birth asphyxia defined as Apgar score at 5 minutes less than 7 among term pregnant women (37 weeks of gestation or more). Materials and Methods A case-control study was conducted at Rajavithi Hospital between January 1,1999 June 30,2005. : Medical records of pregnant women who delivered livebirth at 37 weeks of gestation were included in the study. Medical records of those who delivered before hospital arrival or livebirth with major congenital anomalies were excluded. Women who delivered newborns with Apgar score at 5 minutes less than 7 and 7 were identified as cases and controls, respectively. The proportions of vacuum delivery in a case and control were 18.2% and 7.1% (3), a ratio of case-control to be 1 to 2 and power of 90%, 130 and 260 records for case and control were needed. Thirtytwo main factors consisted of demographic and obstetric characteristics as well as pregnancy complications were considered as risk factors of birth asphyxia and neonatal outcomes. This study was approved by the Ethical Committee of Rajavithi hospital. Statistical analysis Data were analyzed using SPSS version 11.5 (SPSS, Chicago, IL). Demographic data were reported in numbers, percentages and mean with standard deviation. Discrete risk factors between cases and controls were analyzed by chi-square test or Fisher s Exact test as appropriate (Fisher s Exact test was used instead of Chi-square test if there are 25% of the expected count 5 in each cell). Continuous risk factors were analyzed by unpaired t-test or Wilcoxon Ranksum test as appropriate. Multivariate analysis was then used to determine significant risk factors of birth asphyxia adjusting confounding effect. P-value 0.05 was considered as statistical significance. Results During the study period, there were 130 pregnancies with neonatal Apgar score 7 at 5 minutes from of 52,278 livebirths and were matched with 260 pregnancies of newborns with Apgar score 7 at 5 minutes as controls. The mean age of cases and controls were significant difference (mean, 28.2±6.8 years VS 25.9±5.3 years,p=0.001). No significant difference in occupation, gravida, parity, history of abortion, gestational age and neonatal sex were detected. The mean birth weights of cases and controls were 2,933±533 g and 3,230±375 g, respectively (p 0.001, Table 1). The neonatal outcomes with Apgar score 7 were shown in Table 2. Fifteen percent had Apgar score 0-3 (severe depression), 73.6% of them required assisted respirator, 63.2% had abnormal neurological signs and symptoms and 15.8% died in early neonatal period. Eighty-five percent of cases had Apgar score 4 6 (mild to moderate depression). Among these newborns, 60.4% required assisted respirator, 25.2% had neurological signs and symptoms and 3.6% died in early neonatal period. Table 3 shows the association between maternal age and birth asphyxia. The risk of advance age ( 35 years) was significantly high with OR of 4.76 (95%CI , p 0.001). Teenage pregnancy ( 19 years) was not significant. Table 4 shows the association between birth weight and birth asphyxia. Small for gestational age (SGA; 10 percentiles) and large for gestational age (LGA; 90 percentiles) had significant higher risk for Thangwijitra S et al. Risk factors of birth asphyxia in pregnancy 37 complete 55 weeks and over by apgar score less than 7 at 5 minutes birth asphyxia and 3.95 times than appropriate for gestational age (AGA; percentiles). Table 5 shows the association between routes of delivery and birth asphyxia. Vaginal breech delivery has statistically significant risk with OR of 5.64 (95% CI , p=0.028). Forceps extraction, vacuum extraction and cesarean section were not significance. Table 6 shows the association between other factors and birth asphyxia by univariate analysis. Multiple regression analysis is shown in Table 7. Prolonged PROM (premature rupture of membrane) 24 hours, narcotic analgesic used, no antenatal care (no ANC), cord compression, oxytocin usage and meconium-stain amniotic fluid were statistical significant risk for birth asphyxia OR=8.72, 6.78, 5.87, 3.78, 3.50 and 3.16 respectively. Hypertensive disorder in pregnancy (blood pressure 140/90 mmhg during pregnancy which included chronic hypertension, gestational hypertension, preeclampsia-eclampsia, preeclampsia superimposed on chronic hypertension), anemia (Hb 11 gm/dl in 1 st and 3 rd trimester or Hb 10.5 gm/dl in 2 nd trimester), twin and oligohydramios (Amniotic fluid index 5) were not significance. Abnormal fetal heart rate pattern (bradycardia 110 beat/min, tachycardia 160 beat/min, decrease beat to beat variability 5 beat/min, increase beat to beat variability 25 beat/min, repetitive late deceleration: FHR gradual, symmetrical decrease from baseline 15 beat/min at/or after peak of uterine contraction, repetitive moderate to severe varible deceleration: abrupt decrease FHR then return to base line less than 2 min (moderate deceleration 70 beat/min, severe deceleration 70 beat/min lasting 60 sec), prolonged deceleration: FHR deceleration lasting 2 min but less than 10 min) OR=0.03 (95%CI , p 0.001) and diabetes mellites complicating pregnancy (pregestational and gestational diabetes) OR=0.03 (95%CI , p=0.002) were statistically strong benefit on preventing birth asphyxia. Table 1. Demographic characteristics Characteristics Apgar score at 5 minutes p-value 7 (N = 130) 7 (N = 260) Maternal age (years) (10.0) 19 (7.3) (74.5) 231 (88.7) (15.5) 10 (4.0) Gravida (43.8) 108 (41.5) 2 73 (56.2) 152 (58.5) Parity (53.8) 126 (48.5) 1 42 (32.3) 91 (35.0) 2 18 (13.9) 43 (16.5) Abortion (76.9) 211 (81.2) 1 30 (23.1) 49 (18.8) Gestational age (weeks) (96.9) 253 (97.3) 42 4 (3.1) 7 (2.7) 56 Thai J Obstet Gynaecol Table 1. Demographic characteristics (Cont.) Characteristics Apgar score at 5 minutes p-value 7 (N = 130) 7 (N = 260) Occupation Housewife 80 (61.5) 150 (57.7) Shopkeeper 20 (15.4) 40 (15.4) Employee 20 (15.4) 28 (10.8) Officer 10 (7.7) 42 (16.1) Neonatal sex Male 73 (56.2) 138 (53.1) Female 57 (43.8) 122 (46.9) Birth weight (grams) ,000 2, (22.0) 6 (2.4) 2,500 3, (74.0) 250 (96.0) 4,000 6 (4.0) 4 (1.6) Table 2. Outcomes of neonates with Apgar score 7 Complications Apgar score at 5 minutes p value 0 3 (N = 19) 4 6 (N = 111) Required assisted respirator Yes 14 (73.6) 67 (60.4) No 5 (26.4) 44 (39.6) Abnormal Neurological signs and symptoms Yes 12 (63.2) 28 (25.2) No 7 (36.8) 83 (74.8) Neonatal death Yes 3 (15.8) 4 (3.6) No 16 (84.2) 107 (96.4) Table 3. Association of Maternal age and birth asphyxia by multivariate analysis Maternal age Apgar score at 5 minutes Crude Adjusted 95%CI p value (years) 7 (N = 130) 7 (N = 260) OR OR 19 (Teenage) 13(10.0) 19(7.3) (74.5) 231(88.7) (Advance) 20(15.5) 10(4.0) Thangwijitra S et al. Risk factors of birth asphyxia in pregnancy 37 complete 57 weeks and over by apgar score less than 7 at 5 minutes Table 4. Association of birth weight and birth asphyxia by multivariate analysis Birth weight Apgar score at 5 minutes Crude Adjusted 95%CI p value (percentiles) 7 (N = 130) 7 (N = 260) OR OR SGA ( 10) 29 (22.3) 6 (2.3) 0.001 AGA (10-90) 95 (73.1) 250 (96.2) LGA ( 90) 6 (4.6) 4 (1.5) SGA = Small for gestational age, AGA = Average for gestational age LGA = Large for gestational age Table 5. Association of route of delivery and birth asphyxia by multivariate analysis Route of delivery Apgar score at 5 minutes Crude Adjusted 95%CI p value 7(N = 130) 7(N = 260) OR OR Normal delivery 71 (63.12) 200 (76.9) Forceps extraction 5 (3.8) 3 (1.2) Vacuum extraction 8 (6.2) 2 (0.8) Vaginal breech delivery 11 (8.5) 5 (1.9) Cesarean section 35 (26.9) 50 (19.2) Table 6. Association of other factors and birth asphyxia by univariate analysis Factors Apgar score at 5 minutes Crude 95%CI p value 7 (N = 130) 7 (N = 260) OR Prolonged PROM(premature ruptured of membrane 24 hours) Yes 20 (15.4) 2 (0.8) No 110 (84.6) 258 (99.2) 1 1 Narcotic analgesic use Yes 17 (13.1) 6 (2.3) No 113 (86.9) 254 (97.7) 1 1 ANC Yes 107 (82.3) 250 (96.2) 1 1 No 23 (17.7) 10 (3.8) ANC = Antenatal care 58 Thai J Obstet Gynaecol Table 6. Association of other factors and birth asphyxia by univariate analysis (Cont.) Factors Apgar score at 5 minutes Crude 95%CI p value 7 (N = 130) 7 (N = 260) OR Cord compression Yes 24 (18.5) 9 (3.5) No 106 (81.5) 251 (96.5) 1 1 Oxytocin used Yes 39 (30.0) 22 (8.5) No 91 (70.0) 238 (91.5) 1 1 Meconium stain amniotic fluid Yes 52 (40.0) 20 (7.7) No 78 (60.0) 240 (92.3) 1 1 Hypertensive disorder in pregnancy Yes 19 (14.6) 6 (2.3) No 111 (85.4) 254 (97.7) 1 1 Anemia Yes 22 (16.9) 15 (5.8) No 108 (83.1) 245 (94.2) 1 1 Twins Yes 7 (5.4) 2 (0.8) No 123 (94.6) 258 (99.2) 1 1 Oligohydramios Yes 28 (21.5) 2 (0.8) No 102 (78.5) 258 (99.2) 1 1 Abnormal FHR pattern Yes 96 (73.8) 26 (10.0) No 34 (26.2) 234 (90.0) 1 1 Diabetes complicating pregnancy Yes 8 (2.1) 3 (1.2) No 122 (97.9) 257 (99.2) 1 1 ANC = Antenatal care Thangwijitra S et al. Risk factors of birth asphyxia in pregnancy 37 complete 59 weeks and over by apgar score less than 7 at 5 minutes Table 7. Association of other factors and birth asphyxia by multivaiate analysis Factors Crude OR Adjusted OR 95%CI p value Prolonged PROM Narcotic analgesic used No ANC Cord compression Oxytocin usage Meconium stain amniotic fluid Hypertensive disorder in pregnancy Anemia Twins Oligohydramios Abnormal FHR pattern 0.001 Diabetes complicating pregnancy PROM = Premature rupture of the membrane ANC = Antenatal care Discussion From January 1 st, 1999 June 30 th, 2005, rate of birth asphyxia by Apgar score 7 at 5 minutes in pregnancy with gestational age 37 weeks was 2.5:1,000 (130:52,278) which is less than the previous reports. (3-5) This lower rate of the birth asphyxia might be associated with the period of the study because the present study was conducted in the later year which improving the standard of maternal and neonatal care than the previous studies (3-5). Significant risk factors for birth asphyxia in our study were small for gestational age, prolonged PROM, narcotic analgesic used, no ANC care, vaginal breech delivery, advance maternal age ( 35 years), LGA, cord compression, oxytocin usage and meconium-stain amniotic fluid. Ian M et al s study (3) reported that maternal age was not significant risk factor which different from our study. This might be associated with the difference in the population which women in lan M et al (3) had multiple medical complications. For this reason, those women were received special care and resulting in delivery of non-asphyxia neonates. Kovavisarach E et al (6) reported oxytocin usage was not significant risk factor that difference from the present study. This might be because Kovavisarach et al (6) included preterm pregnancy and this condition was contraindicated for oxytocin usage. Ibrahim S et al (7) reported 71% of pregnancy with asphyxia newborns had visited in antenatal care which they concluded this reflects the poor perinatal services offered in those maternity homes or hospitals. Teenage pregnancy ( 19 years), gravida, parity, history of abortion, posterm pregnancy ( 42 weeks), occupation, thyroid disorder, hypertensive disorder in pregnancy, anemia, placenta previa, twin, oligohydramios, cesarean section, forceps extraction and vacuum extraction were not significant risk factors. Boo NY et al (8), Ian M et al (3) and Kaye D et al (9) reported vacuum extraction and forceps extraction were significant risk factors for birth asphyxia. This difference might be associated with the operative vaginal assisted delivery in the present study were preformed following the non-reassuring fetal heart rate pattern indication that were not true fetal acidosis and delivery with non- 60 Thai J Obstet Gynaecol complications. Negative impact on birth asphyxia or strong benefits on preventing birth asphyxia were abnormal fetal heart rate pattern and diabetes mellitus complicating pregnancy. In previous study, abnormal mellitus fetal heart rate pattern was significant risk factor for birth asphyxia (3-8,10,11). In our study, most of abnormal fetal heart rate pattern was diagnosed as non-reassuring fetal status and immediate cared and dilivered by cesarean section. In the previous study (3) reported diabetes mellitus was not siginificant risk factor for birth asphyxia which was difference from our study. This may be associated with most of diabetes mellitus complicating pregnancy in our study were class A and received special cares and management which result the rate of elective cesarean section was doubling may be reflected the cause of prevention of birth asphyxia. Apgar score at 5 minutes of gestational age 37 weeks was strongly associated with birth asphyxia that demonstrated by the neonatal outcomes, the more severe asphyxia (Apgar score 0 3), the higher incidence of severe neonatal morbidity and mortality including neonatal death, neurological signs and symptoms and required assisted respirator similar to the study of Oswyn et al (4). This study had recruited large number of risk factors. Variation in number of risk factors is unavoidable. Some categories had no specific risk factors in control group at all. This may reflect either rare events or too small sample sizes. Further study on specific risk factors may give the correction or confirmation to this study. References 1. Marrin M, Paes BA. Birth asphyxia: Does the apgar score have diagnostic value?. Obstet Gynecol 1988; 72: Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Gilstrap LC III, Wenstrom KD. Diseases and injuries of the fetus and newborn. In: Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Gilstrap LC III, Wenstrom KD, editors. Williams obstetrics. 22 nd ed. New York: The McGnaw-Hill companies, 2005: Ian M,Lars L,Klara T,Aimon N,Anders O,Eva T. Influence of maternal, obstetric and fetal risk factors on prevalence of birth asphyxia at term in Swedish urban population. Acta Obstet Gynecol Scand 2002; 81: Oswyn G, Vince JD, Fricsen H. Perinatal asphyxia at Port Moresby General Hospital:a study of incidence, risk factors and outcome. P N G Med J 2000; 43: Matthew E,Nilu M,Dharma S,Anthony M. Risk factors for neonatal encephalopathy in Kathmandu, Nepal. BMJ 2000; 320: Kovavisarach E, Juntasom C. Risk factors of delivery of low Apgar score newborn below 7 at 1 minute. J Med Assoc Thai 1999; 82: Ibrahim S, Parkash J. Birth asphyxia. J Pak Med Assoc 2002; 52: Boo NY, Lye MS. Factors associated with clinically significant perinatal asphyxia in Malaysian neonates. J Trop Pediatr 1991; 38: Kaye D. Antenatal and intrapartum risk factors for birth asphyxia. East Afr Med J 2003; 80: Asakura H,Ichikawa H,Nakabayashi M,Ando K,Kaneko K,Kawabata M,et al. Perinatal risk factors related to neurologic outcomes of term newborns with asphyxia at birth. J Obstet Gynaecol Res 2000; 26: Suka M, Sugimori H, Nakamura M,Haginiwa K, Yoshida K. Risk factors of low apgar score in japanese full term deliveries. J Epidemiol 2002; 12: Conclusion Risk factors significantly associated with birth asphyxia in pregnancy 37 weeks were SGA, prolonged PROM, narcotic analgesic used, no antenatal care, vaginal breech delivery, advance maternal age, LGA, cord compression, oxytocin usage and meconiumstained amniotic fluid. Women having these risk factors should be intensively counseled and closely observed during labor and delivery. Thangwijitra S et al. Risk factors of birth asphyxia in pregnancy 37 complete 61 weeks and over by apgar score less than 7 at 5 minutes ป จจ ย เส ยง ต อ ภาวะ การ ขาด ออกซ เจน ของ ทารก แรกเก ด ใน หญ ง ต งครรภ อาย ครรภ ต งแต 37 ส ปดาห โดย คะแนนแอ พการ ท 5 นาท น อยกว า 7 ส รางค ท พย ต ง ว จ ตร, ชำานาญ ศร ประโมทย, ส ขาวด กาญ จน ว ฒน ว ตถ ประสงค : เพ อ ศ กษา ป จจ ย เส ยง ต อ ภาวะ การ ขาด ออกซ เจน ของ ทารก แรกเก ด ใน หญ ง ต งครรภ อาย ครรภ ต งแต 37 ส ปดาห เป นต นไป โดย คะแนนแอ พการ ท 5 นาท น อยกว า 7 ร ปแบบ การ ว จ ย: การ ว จ ย เช ง ว เคราะห แบบ ย อนหล ง ( case-control study) ว สด และ ว ธ การ: ศ กษา ข อม ล ย อน หล งจาก ทะเบ ยน ประว ต หญ ง ต งครรภ อาย ครรภ ต งแต 37 ส ปดาห เป นต นไป ใน โรงพยาบาล ราช ว ถ
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