Preterm Labor
¢Â Preterm Birth
1. Definition
(1) Prematurity : Gestational age < 37wks
(2) Low birth weight (LBW) : <2500g
(3) Very Low birth weight (VLBW) : <1500g
(4) Extremely Low birth weight (ELBW) : <1000g
(5) Small for gestational age : birthweight below the 10th percentile
(6) Appropriate for gestational age : between the 10th and 90th percentiles
(7) Large for gestational age : birthwight above the 10th percentile
2. Causes of preterm birth
1) Medical and obstetrical complications
* 28% - preeclampsia, fetal distress, fetal growth restriction, abruptio placentae, fetal death
* 72% - spontaneous preterm labor with or without ruptured membranes
+ Ãß°¡·Î placenta previa, multiple gestation ¶ÇÇÑ ÈçÇÑ ¿øÀÎÀÌ´Ù.
2) Lifestyle factors
: cigarette smoking, poor nutrition, poor weight gain during pregnancy, use of drugs such as cocaine or alcohol
: other maternal factors - young maternal age, poverty, short stature, occupational factors, psychological stress
3) Genetic factors
4) Chorioamniotic infection
: 20% of women - no evidence of overt clinical infection and with intact fetal membranes
: Pathophysiology (figure 28-8)
: amniocentesis - pregnancy outcomeÀ» ÁÁ°Ô ÇÑ´Ù´Â º¸°í´Â ¾øÁö¸¸ amniotic fluid WBC count, low glucose, high interleukin-6, Gram staining, Culture·Î Áø´ÜÇÒ ¼ö´Â ÀÖ´Ù.
: microorganism¿¡ ÀÇÇØ membrane rupture, perterm labor·Î ÁøÇàÇÒ ¼ö ÀÖ´Ù.
5) Bacterial vaginosis
: the normal, hydrogen peroxide-producing lactobacillu-predominant vaginal flora is replaced with anaerobic bacteria(Gardnerella vaginalis, Mobiluncus species, Mycoplasma hominis)
: MechanismÀº amniotic fliud infection°ú °°´Ù.
: Diagnostic feature
(1) Vagnial pH > 4.5
(2) An amine odor when vaginal secretions are mixed with potassium hydroxide
(3) Vaginal epithelial cells heavily coated with bacilli - 'clue cells'
(4) A homogeneous vaginal discharge
(5) Gram staining of vaginal secretion
3. Risk factors for preterm birth
1) Prior preterm birth
2) Cervical dilatation
: Asymptomatic cervical dilatation after midpregnancy
: Preterm birthÀÇ 27%Á¤µµ°¡ 26-30ÁÖ¿¡ 2-3cmÀÇ dilatationÀÌ ÀÖÀ½
3) Cervical length
: mean cervical length at 24 weeks = about 35mm
- cervical length°¡ ªÀ»¼ö·Ï preterm birth rate°¡ Áõ°¡
±×¸² 27-9
4) Sign & Symptoms
: painful or painless uterine contractions, pelvic pressure, menstrual-like cramp, watery or bloody vaginal discharge, and pain in the low back
=> impending preterm birth¿Í °ü·ÃµÈ Áõ»óµé·Î¼ preterm labor 24½Ã°£ Àü¿¡¸¸ ³ªÅ¸³ª±â ¶§¹®¿¡ late warning signÀ¸·Î º¼ ¼ö ÀÖ´Ù.
4) Fetal fibronectin
: detection of fetal fibronectin in cervicovaginal secretions prior to membrane rupture
( >50 ng/mL)
5) Ambulatory uterine contraction testing
: ¡è uterine activity beginning at about 30 weeks
: but home uterine activity monitoring is ineffective in the prevention of preterm birth
4. Management of preterm labor
=> correct identification & whether there is accompanying membrane rupture
1) Diagnosis
: True vs False labor
- True labor´Â cervical effacement & dilatationÀ» µ¿¹ÝÇÔ
- ±×·¸Áö¸¸ termÀü¿¡ ºÐ¸¸ÇÏ´Â »ê¸ð Áß¿¡ Braxton Hick contraction(irregular, nonrhythmical and either painful or painless)°ú ºñ½ÁÇÑ ¾ç»óÀ» º¸ÀÌ´Â °æ¿ì°¡ µå¹°Áö ¾Ê°Ô ÀÖ¾î false labor·Î À߸ø Áø´ÜµÉ ¼öµµ ÀÖ´Ù.
: Criteria of preterm labor (American College of Obstetricians and Gynecologists, 1997)
(1) Contractions occurring at a frequency of four in 20 minutes or eight in 60 minutes plus progressive change in the cervix
(2) Cervical dilatation > 1cm
(3) Cervical effacement ¡Ã80%
2) Management
=> intentional delivery¸¦ ÇØ¾ß ÇÏ´Â maternal or fetal indicationÀÌ ¾ø´Â ÇÑ, management´Â preterm birth¸¦ ¾ïÁ¦Çϰųª žư¡ extrauterine environment¿¡ ÀûÀýÇÏ°Ô ´ëóÇÒ ¼ö ÀÖ´Â ´É·ÂÀ» Ű¿öÁÖ´Â °ÍÀ» ¸ñÇ¥·Î ÇÑ´Ù.
* Preterm premature rupture of the membrane(PPROM)
- Two primary forms of approach
(1) Nonintervention or expectant management, in which spontaneous labor is simply awaited
(2) Intervention that may include glucocorticoids, given with or without tocolytic agents to arrest preterm labor in order that the corticosteroids have sufficient time to induce fetal maturation
- Natural history of PPROM
: ÀÔ¿ø´ç½Ã 75%´Â ÀÌ¹Ì labor ´Ü°èÀ̰í, 5%´Â ´Ù¸¥ complicationÀ¸·Î delivery, 10%´Â 48hr³»¿¡ spontaneous delivery, 7%¸¸ÀÌ ruptureµÈ ÈÄ 48hrÀÌ»ó Áö¿¬µÉ ¼ö ÀÖ´Ù.
: ´ëºÎºÐÀº 1ÁÖÀÏ ³»¿¡ labor¿¡ µé¾î°£´Ù. => ¡Å Hospitalization ÇÊ¿ä
* Preterm labor with intact fetal membranes
: PPROM°ú °ÅÀÇ µ¿ÀÏÇÏ°í °¡´ÉÇϸé 34ÁÖ ÀÌÀü¿¡ deliveryÇÏÁö ¾Êµµ·Ï ÇÏ´Â °ÍÀÌ Áß¿ä
* Corticosteroid therpy
- Betamethasone(12mg IM in two doses 24 hr apart)
: Åõ¿© ½ÃÀÛ ÈÄ Àû¾îµµ 24½Ã°£µ¿¾È delivery¸¦ ¾ïÁ¦Çϸé 34ÁÖ ¹Ì¸¸¿¡ ÅÂ¾î³ infant¿¡°Ô¼ RDSÀÇ risk¸¦ ÁÙÀÏ ¼ö ÀÖ´Ù. 7ÀϱîÁö Åõ¿©ÇÏ´Â °ÍÀÌ ¿Ï·áÇÏ´Â °Í.
- Adverse effect
: short-term maternal effects
- pulmonary edema, infection, difficult glucose control in diabetic women
* Antenatal phenobarbital and vitamin K therapy
- neonatal intracranial hemorrahge¸¦ ÁÙÀ̱â À§ÇØ »ç¿ëµÇÁö¸¸, È¿°ú´Â º°·Î ¾ø´Â °ÍÀ¸·Î º¸ÀÓ
(Thorp et al. 1995)
* Tocolytic therapy
(1) Bed rest - no conclusive
(2) Hydration and sedation - not found to be more beneficial than bed rest
(3) ¥â-adrenergic receptor agonists
=> delay delivery for no more than 48 hours
- Ritodrine (Yutopar)
: Side effects - maternal tachycardia, hypotension, apprehension, chest tightness or pain, pulmonary edema, death, hyperglycemia, hyperinsulinemia, hypokalemia, lactic and ketoacidosis, emesis, headaches, tremor, fever, hallucinations
(4) Magnesium sulfate
- presumably calcium antagonist effect
- 4g loading dose -> continuous infusion of 2g/hr
- dose-dependent toxocity¿¡ À¯ÀÇ => ÀÚ¼¼ÇÑ °ÍÀº PBLÇß´ø °Í ÂüÁ¶
(5) Prostaglandin inhibitors
; aspirin and other salicylates, indomethacin, naproxen, and sulindac
- adversely affect on fetus => ¡Å ³Î¸® ÀÌ¿ëµÇÁö ¸øÇÔ
(closure of the ductus arterio³â, necrotizing enterocolitis, intracranial hemorrahge, etc.)
- ritodrine¿¡ ºñÇØ 48ÀÌ»óÀ¸·Î ¹®¸¸À» Áö¿¬½ÃŰ´Â È¿°ú°¡ ÁÁ°í materal side effect´Â ÀûÁö¸¸, neonatal morbidity°¡ Áõ°¡ÇÏ´Â ´ÜÁ¡ÀÌ ÀÖ´Ù.
(6) Calcium channel blocker
- ritodrineº¸´Ù È¿°ú´Â ´õ ÁÁÁö¸¸ maternal side effect°¡ ½É°¢ÇÏ´Ù
(Systemic vasodilatory effect -> maternal hypotension -> ¡éuteroplacental perfusion)
- enhancing the magnesium toxicity!!
(7) Nitric oxide
- IV nitroglycerinÀº magnesuim sulfate¿Í tocolytic effect ºñ½Á
(8) Combination therapy
- single drugÀ¸·Î ÃæºÐÇÏÁö ¾ÊÀ» ¶§, ½ÃµµÇØ º¼ ¼ö ÀÖ´Ù.
1. Definition
(1) Prematurity : Gestational age < 37wks
(2) Low birth weight (LBW) : <2500g
(3) Very Low birth weight (VLBW) : <1500g
(4) Extremely Low birth weight (ELBW) : <1000g
(5) Small for gestational age : birthweight below the 10th percentile
(6) Appropriate for gestational age : between the 10th and 90th percentiles
(7) Large for gestational age : birthwight above the 10th percentile
2. Causes of preterm birth
1) Medical and obstetrical complications
* 28% - preeclampsia, fetal distress, fetal growth restriction, abruptio placentae, fetal death
* 72% - spontaneous preterm labor with or without ruptured membranes
+ Ãß°¡·Î placenta previa, multiple gestation ¶ÇÇÑ ÈçÇÑ ¿øÀÎÀÌ´Ù.
2) Lifestyle factors
: cigarette smoking, poor nutrition, poor weight gain during pregnancy, use of drugs such as cocaine or alcohol
: other maternal factors - young maternal age, poverty, short stature, occupational factors, psychological stress
3) Genetic factors
4) Chorioamniotic infection
: 20% of women - no evidence of overt clinical infection and with intact fetal membranes
: Pathophysiology (figure 28-8)
: amniocentesis - pregnancy outcomeÀ» ÁÁ°Ô ÇÑ´Ù´Â º¸°í´Â ¾øÁö¸¸ amniotic fluid WBC count, low glucose, high interleukin-6, Gram staining, Culture·Î Áø´ÜÇÒ ¼ö´Â ÀÖ´Ù.
: microorganism¿¡ ÀÇÇØ membrane rupture, perterm labor·Î ÁøÇàÇÒ ¼ö ÀÖ´Ù.
5) Bacterial vaginosis
: the normal, hydrogen peroxide-producing lactobacillu-predominant vaginal flora is replaced with anaerobic bacteria(Gardnerella vaginalis, Mobiluncus species, Mycoplasma hominis)
: MechanismÀº amniotic fliud infection°ú °°´Ù.
: Diagnostic feature
(1) Vagnial pH > 4.5
(2) An amine odor when vaginal secretions are mixed with potassium hydroxide
(3) Vaginal epithelial cells heavily coated with bacilli - 'clue cells'
(4) A homogeneous vaginal discharge
(5) Gram staining of vaginal secretion
3. Risk factors for preterm birth
1) Prior preterm birth
2) Cervical dilatation
: Asymptomatic cervical dilatation after midpregnancy
: Preterm birthÀÇ 27%Á¤µµ°¡ 26-30ÁÖ¿¡ 2-3cmÀÇ dilatationÀÌ ÀÖÀ½
3) Cervical length
: mean cervical length at 24 weeks = about 35mm
- cervical length°¡ ªÀ»¼ö·Ï preterm birth rate°¡ Áõ°¡
±×¸² 27-9
4) Sign & Symptoms
: painful or painless uterine contractions, pelvic pressure, menstrual-like cramp, watery or bloody vaginal discharge, and pain in the low back
=> impending preterm birth¿Í °ü·ÃµÈ Áõ»óµé·Î¼ preterm labor 24½Ã°£ Àü¿¡¸¸ ³ªÅ¸³ª±â ¶§¹®¿¡ late warning signÀ¸·Î º¼ ¼ö ÀÖ´Ù.
4) Fetal fibronectin
: detection of fetal fibronectin in cervicovaginal secretions prior to membrane rupture
( >50 ng/mL)
5) Ambulatory uterine contraction testing
: ¡è uterine activity beginning at about 30 weeks
: but home uterine activity monitoring is ineffective in the prevention of preterm birth
4. Management of preterm labor
=> correct identification & whether there is accompanying membrane rupture
1) Diagnosis
: True vs False labor
- True labor´Â cervical effacement & dilatationÀ» µ¿¹ÝÇÔ
- ±×·¸Áö¸¸ termÀü¿¡ ºÐ¸¸ÇÏ´Â »ê¸ð Áß¿¡ Braxton Hick contraction(irregular, nonrhythmical and either painful or painless)°ú ºñ½ÁÇÑ ¾ç»óÀ» º¸ÀÌ´Â °æ¿ì°¡ µå¹°Áö ¾Ê°Ô ÀÖ¾î false labor·Î À߸ø Áø´ÜµÉ ¼öµµ ÀÖ´Ù.
: Criteria of preterm labor (American College of Obstetricians and Gynecologists, 1997)
(1) Contractions occurring at a frequency of four in 20 minutes or eight in 60 minutes plus progressive change in the cervix
(2) Cervical dilatation > 1cm
(3) Cervical effacement ¡Ã80%
2) Management
=> intentional delivery¸¦ ÇØ¾ß ÇÏ´Â maternal or fetal indicationÀÌ ¾ø´Â ÇÑ, management´Â preterm birth¸¦ ¾ïÁ¦Çϰųª žư¡ extrauterine environment¿¡ ÀûÀýÇÏ°Ô ´ëóÇÒ ¼ö ÀÖ´Â ´É·ÂÀ» Ű¿öÁÖ´Â °ÍÀ» ¸ñÇ¥·Î ÇÑ´Ù.
* Preterm premature rupture of the membrane(PPROM)
- Two primary forms of approach
(1) Nonintervention or expectant management, in which spontaneous labor is simply awaited
(2) Intervention that may include glucocorticoids, given with or without tocolytic agents to arrest preterm labor in order that the corticosteroids have sufficient time to induce fetal maturation
- Natural history of PPROM
: ÀÔ¿ø´ç½Ã 75%´Â ÀÌ¹Ì labor ´Ü°èÀ̰í, 5%´Â ´Ù¸¥ complicationÀ¸·Î delivery, 10%´Â 48hr³»¿¡ spontaneous delivery, 7%¸¸ÀÌ ruptureµÈ ÈÄ 48hrÀÌ»ó Áö¿¬µÉ ¼ö ÀÖ´Ù.
: ´ëºÎºÐÀº 1ÁÖÀÏ ³»¿¡ labor¿¡ µé¾î°£´Ù. => ¡Å Hospitalization ÇÊ¿ä
* Preterm labor with intact fetal membranes
: PPROM°ú °ÅÀÇ µ¿ÀÏÇÏ°í °¡´ÉÇϸé 34ÁÖ ÀÌÀü¿¡ deliveryÇÏÁö ¾Êµµ·Ï ÇÏ´Â °ÍÀÌ Áß¿ä
* Corticosteroid therpy
- Betamethasone(12mg IM in two doses 24 hr apart)
: Åõ¿© ½ÃÀÛ ÈÄ Àû¾îµµ 24½Ã°£µ¿¾È delivery¸¦ ¾ïÁ¦Çϸé 34ÁÖ ¹Ì¸¸¿¡ ÅÂ¾î³ infant¿¡°Ô¼ RDSÀÇ risk¸¦ ÁÙÀÏ ¼ö ÀÖ´Ù. 7ÀϱîÁö Åõ¿©ÇÏ´Â °ÍÀÌ ¿Ï·áÇÏ´Â °Í.
- Adverse effect
: short-term maternal effects
- pulmonary edema, infection, difficult glucose control in diabetic women
* Antenatal phenobarbital and vitamin K therapy
- neonatal intracranial hemorrahge¸¦ ÁÙÀ̱â À§ÇØ »ç¿ëµÇÁö¸¸, È¿°ú´Â º°·Î ¾ø´Â °ÍÀ¸·Î º¸ÀÓ
(Thorp et al. 1995)
* Tocolytic therapy
(1) Bed rest - no conclusive
(2) Hydration and sedation - not found to be more beneficial than bed rest
(3) ¥â-adrenergic receptor agonists
=> delay delivery for no more than 48 hours
- Ritodrine (Yutopar)
: Side effects - maternal tachycardia, hypotension, apprehension, chest tightness or pain, pulmonary edema, death, hyperglycemia, hyperinsulinemia, hypokalemia, lactic and ketoacidosis, emesis, headaches, tremor, fever, hallucinations
(4) Magnesium sulfate
- presumably calcium antagonist effect
- 4g loading dose -> continuous infusion of 2g/hr
- dose-dependent toxocity¿¡ À¯ÀÇ => ÀÚ¼¼ÇÑ °ÍÀº PBLÇß´ø °Í ÂüÁ¶
(5) Prostaglandin inhibitors
; aspirin and other salicylates, indomethacin, naproxen, and sulindac
- adversely affect on fetus => ¡Å ³Î¸® ÀÌ¿ëµÇÁö ¸øÇÔ
(closure of the ductus arterio³â, necrotizing enterocolitis, intracranial hemorrahge, etc.)
- ritodrine¿¡ ºñÇØ 48ÀÌ»óÀ¸·Î ¹®¸¸À» Áö¿¬½ÃŰ´Â È¿°ú°¡ ÁÁ°í materal side effect´Â ÀûÁö¸¸, neonatal morbidity°¡ Áõ°¡ÇÏ´Â ´ÜÁ¡ÀÌ ÀÖ´Ù.
(6) Calcium channel blocker
- ritodrineº¸´Ù È¿°ú´Â ´õ ÁÁÁö¸¸ maternal side effect°¡ ½É°¢ÇÏ´Ù
(Systemic vasodilatory effect -> maternal hypotension -> ¡éuteroplacental perfusion)
- enhancing the magnesium toxicity!!
(7) Nitric oxide
- IV nitroglycerinÀº magnesuim sulfate¿Í tocolytic effect ºñ½Á
(8) Combination therapy
- single drugÀ¸·Î ÃæºÐÇÏÁö ¾ÊÀ» ¶§, ½ÃµµÇØ º¼ ¼ö ÀÖ´Ù.