Multiple gestation: time interval between delivery of the first and second twins.

A clinical investigation was undertaken to challenge the commonly accepted view that the interval between the birth of the first and second twins should be preferably within 15 minutes and certainly no more than 30 minutes. During 1981 and 1982, 115 patients with live-born twins at 34 or more weeks' gestation underwent an attempted vaginal delivery at four regional perinatal centers. The interval between vaginal delivery of the first and second twins (mean, 21 minutes, range, one to 134 minutes) was 15 minutes or less in 70 (61%) cases and more than 15 minutes in 45 (39%) cases. Excluding conditions associated primarily with prematurity, all second twins delivered beyond 15 minutes did well despite the delay and had no signs of excess trauma or low five-minute Apgar scores. Maternal complications were also uncommon, although combined vaginal-abdominal delivery was more frequent if there was a delay of more than 15 minutes (eight of 45 versus two of 70, P less than .02). The authors conclude that if there is continuous fetal and uterine monitoring, a time restriction for the delivery interval between the first and second infants is not necessary.

Multiple Gestation: Time Interval Between Delivery of the First and Second Twins WILLIAM F. RAYBURN/ MD/ JUSTIN P. LAVIN/ Jr/ MD/ MENACHEM MIODOVNIK, MD/ AND MICHAEL W. V ARNER/ MD A clinical investigation was undertaken to challenge the commonly accepted view that the interval between the birth of the first and second twins should be preferably within 15 minutes and certainly no more than 30 minutes. During 1981 and 1982, 115 patients with live-born twins at 34 or more weeks' gestation underwent an attempted vaginal delivery at four regional perinatal centers. The interval between vaginal delivery of the first and second twins (mean, 21 minutes, range, one to 134 minutes) was 15 minutes or less in 70 (61%) cases and more than 15 minutes in 45 (39%) cases. Excluding conditions associated primarily with prematurity, all second twins delivered beyond 15 minutes did well despite the delay and had no signs of excess lrauma or low five-minute Apgar scores. Maternal complications were also uncommon, although combined vaginal-abdominal deliv­ery was more frequent if there was a delay of more than 15 minutes (eight of 45 versus two of 70, P < .02). The authors conclude that if there is continuous fetal and uterine moni­toring, a time restriction for the delivery interval between the first and second infants is not necessary. (Obstet Gynecol 63:502, 1984) A patient whose pregnancy is complicated by twin gestation requires early diagnosis and careful surveil­lance during the antepartum and intrapartum periods. Preterm delivery is a frequent occurrence, and perina­tal mortality decreases significantly if the birth weight is 2000 g or more or if the gestational age is 34 weeks or more. l-:'i The route of delivery is determined largely by gesta­tional age and the presentation of the first twin. Cesarean section has been advocated as the optimal route of delivery between 26 and 33 weeks' gesta- From tile Obstetri~ Divisions, ,Departments of Obstetrics and Gy"e­col? K~' the Ulllver~lty of Mldllgan Women's Hospital, All!! Arbor, Mlchrgan, Akron ~It~ Hospital,. Akrol!, Ohio, llniversity of Cincinnati MedlCIII Center, CmCllllllltl, 01110, and University of Iowa Hospitals llnd Clinics, Iowa City, Iowa. 502 0029-7844/84/$3.00 tion. 6,7 If birth occurs at 34 weeks or more, the first fetus is usually delivered in the same manner as a singleton fetus, with the indications for cesarean sec­tion being the same. Vaginal delivery may be attempt­ed if the first twin is in cephalic presentation. 1.6,8--10 Watchful expectancy while monitoring the fetal heart rate and the uterine contraction pattern is recommend­ed throughout labor. An intrapartum dilemma unique to twin gestations involves the interval that should be allowed between delivery of the first and second fetuses. The tempta­tion to perform an expedient extraction is great, since uterine inertia, umbilical cord prolapse, placental abruption, fetal hypoxia, and stillbirth are concerns. 2,4 An accepted view for many years has been that the interval between the delivery of twin infants should be preferably within 15 minutes and certainly not more than 30 minutes; otherwise, the risk to the second infant from diminished placental circulation has been presumed to rise with elapsed time in utero after delivery of the first infant. 2-4.11-15 This guideline may not be applicable to the present standard of obstetric practice, as these time restraints were rec~mmended initially when continuous intra­partum fetal monitoring and intensive care nurseries were either unavailable or in the early stages of devel­opment. Perinatal mortality in twin gestations is now considered to be lower than previously reported, with survival rates approximately the same for the first and the second fetuses.'·3.IO.IH Most deaths are attrib­utable to prematurity rather than to twinning per se.I.5.9.IO.I6-20 Furthermore, the delivery of the second twin in the least traumatic manner is an especially major concern today and may not be accomplished easily within the previously proposed interval because of uterine inertia. A review of the literature disclosed few data to challenge strongly this commonly held interval guide­line. r ouppila et all6 in 1975 reported that a delay in Obstetrics & Gynecology i,,~rt:y of the ,.' :>t."~~tiil morta I ~ze i.-,traparl1 Ii. :Jt"",:c,,:dy, a ',.• .'. ... '".:5 tl:i:i1 publi j' ~,:=:-.:2li\~ery· i 1 j rf\l:l gesta .:rl.:~W.k.en to , ±~ ~~((lnd t\\ .\... :.•. ~.'.'. :Xi: i.f the ;!~7Ed dusely \L;;t'rials a i 1 t \ I t ( { t i I ( r r!'ti:~rinata in ugina\ d wa5 in .... esti~ datI at fouI Michigan, U tal, and Un t>etr,.,·een pe ing the sam Prutocols na\ delivey; t:onic fetal lion of an Extemal n tronic ute transducel first twin itor.:\l·:H P cervix We be-.:ame a Two 0\ attendan made, al as a sing The S{ Table 1_ Mean m< (range Race Parity Meang' (rang­Antepa Case.s;'t Akro Univ l!nh Uni' VOL lore, the first manner as a cesarean sec· lY be attempt· ~nta tion. 1.6.8-lfl the fetal heart .s recomn1.end. win gestations )wed between ;. The teITIpta· is grea t, SincE pse, placental lre concerns?" ; been tha t the fants should b! ainly no t mOlE to the seconJ lation has been in utero aflel e to the pl'esen: ~ time I'Q!:>trainli ll1linLlOUH inlra' e cnrl~ 1\ LU'HCrif. slagt'H \ If dcvc\ estutlm1B, is 11011 y rep()\'tnd, will ne fo1' the /ll! leathH nrC! aUti~ :0 twinning pi ~ry of the S(]CO~ is an Qspccia~ be accorn plish~ l intcrVt\1 bccauj sed few data I Id interval guidt d th<1t a delayi etries t:r Gymco1ol' delivery of the second twin did not increase the risk of perinatal mortality. Given the current level of obstetric care, intrapartum stillbirth of a second twin is now, fortunately, a rare event. However, little information has been published about the relationship between the interdelivery interval and maternal or fetal morbidity in twin gestation. The present study was therefore undertaken to test the authors' clinical impression that the second twin may be delivered safely beyond this limit if the fetus and labor continue to be mon­itored closely. Materials and Methods The perinatal outcome of all twin pregnancies ending in vaginal delivery at 34 weeks' gestation or beyond was investigated during 1981 and 1982. A review of data at four regional perinatal centers (University of Michigan, University of Cincinnati, Akron City Hospi­tal, and University of Iowa) permitted a comparison between perinatal outcome at several institutions dur­ing the same period. Protocols at each institution for the anticipated vagi­nal delivery of twins were essentially the same. Elec­tronic fetal heart rate monitoring involved the applica­tion of an internal electrode on the first twin and an external receiver on the second. Simultaneous elec­tronic uterine monitoring involved connecting the transducer measuring the intrauterine pressure of the first twin to the transducer of the second fetal mon­itOr. 20 ,21 Any regional anesthesia was delayed until the cervix was dilated 5 cm or more. If uterine inertia became apparent, oxytocin was used cautiously. Two obstetricians and a neonatal care team were in attendance at delivery. A large episiotomy was usually made, and the first twin was delivered the same way as a singleton. The second twin was often visualized ultrasonically to monitor the heart rate and presentation. Continuous monitoring of the fetal heart rate was undertaken while watching for any excess vaginal bleeding. Halo­thane was used infrequently to guide the second twin into the pelvis. OxytOcin was also used if uterine contractions subsided within ten minutes after deliv­ery of the first twin. In all patients enrolled in the study, the gestational age was 34 weeks or more (or the birth weight of either liveborn infant was 2000 g or more if gestational age was uncertain), and the first infant was delivered vaginally from a cephalic presentation. Obstetric data gathered from chart review included any other ante­partum complication, the interval between delivery of the two infants, the presentation and route of delivery of the second infant, and any maternal complication during delivery. Information collected about the new­born infants included birth weight, five-minute Apgar score, need for intensive care nursery admission, and any noteworthy neonatal complication during or short­ly after delivery. Any maternal or neonatal complications were com­pared with the interval between the delivery of the two infants using the X2 test. A P value less than ,05 was considered statistically significant. Results During the two-year period, 21,420 patients were de­livered at the four institutions, and 294 (1.4%) had twin gestations. Among the 186 pregnancies with liveborn twins born at or beyond 34 weeks' gestation, 117 (63%} were delivered vaginally. Two of these pregnanCies were excluded from consideration because the first twin had been in a breech presentation. The profile of the 115 study pregnancies is shown in Table 1. The maternal age, race, parity, and gestational age at delivery were similar regardless of the interde- Table 1. Profiles of Pregnancies with Twin Gestations (N = 115) Interval between delivery of twins :::=15 min (N = 711) 16-30 min (N = 28) >30 min (N = 17) Total (N = 115) Mean maternal age (yr) 25 24 25 25 (range) (15-35) (17-34) (17-40) (15-40) Race 48 (69%) white 19 (68%) while 9 (53%) white 76 (66%) white Parity 23 (33%) nulliparous 9 (32%) nulliparous 5 (29%) nulliparous 37 (32%) nulliparous Mean gestational age (wk) 37 37 37 37 (range) (34-411) (34-43) (34-40) (34-43) Antepartum complications 14 (211%) 5 (18%) 3 (18%) 22 (19%) Cases/hospital Akron City 24 (34%) 7 (25%) 4 (24%) 35 (30%) Univ. Michigan 18 (26%) 7 (25%) 4 (24%) 29 (25%) Univ. Cincinnati B (11%) 9 (32%) 8 (47%) 25 (22%) Univ. Iowa 211 (29%) 5 (18%) 1 (5%) 26 (23%) VOL. 63, NO.4, APRIL 1984 Rayburn et al Time Intervals in Multiple GestatiOllS 503 Table 2. Relationship Between Perinatal Events in the Second Twin and the Delivery Interval Between Twins Interval :s15 min 16-30 min E\'ent (N = 70) (N = 28) Breech presentation of second twin 31 (44%) 7 (25%) Vaginal-abdominal delh'ery 2 (3%) 5 (18%) 5-minute Apgar score <7 2 (3%) 3 (11%) Birth weight < first twin 13 (19%) 9 (32%) ~ first twin 39 (55%) 12 (43%) > first twin 18 (26%) 7 (25%) Intensive care nursery admission 8 (12%) 6 (21%) livery interval. Antepartum complications occurred in appr"oximately one fifth of the pregnancies, with preg­nancy- induced hypertension being the most frequent complication. Types of anesthesia used in delivering the 105 patients transvaginally included pudendal or local (71), epidural (26), and general (eight) anesthesia. Epidural anesthesia was not used more frequently when there was a delay in delivery of the second twin. A breech presentation in 45 of the second twin fetuses was not more common if the delivery of that twin occurred after the first 15 minutes (Table 2). The interval between vaginal delivery of the first and second twins averaged 21 minutes (range one to 134 minutes). The distribution of intervals in the 115 cases is shown in Figure 1. The elapsed interval was within 15 minutes in 70 (61 %) cases, within 16 to 30 minutes in 28 (24%) cases, and more than 30 minutes in 17 (15%) cases. Oxytocin infusion for augmenting or inducing uterine contractions after a IS-minute interdelivery interval was necessary in 19 (42%) of the 45 cases. The mode of delivery of the second twin is compared with the interval between vaginal delivery of the first and second twins in Table 3, Most cephalically present- 28 '0 16 <..: ~ 12 a.. B 4 a LI?mI ! ! ! ! ! I , ! , , 1 r frL--J 20 25 30 35 40 45 50 55 60 65 70 75 130 134 Interval (min.) Figure 1. Percentage distribution of intervals between delivery of the first and second twins in 115 pregnancies. 504 Rayburn et al Time Intervals in Multiple Gestations P value s15 min <15 min <30 min liS 16-30 >30 min vs >15 vs >30 min liS (N = 17) min min >30 min 7 (41 %) .21 (1 df) .75 (1 dJ) .10 (2 df) 3 (17%) .02 (1 df) .34 (1 dJ) .02 (2 df) 0 ,61 (1 dfl .76 (1 dJ) .14 (2dfl 5 (29%) .28 (2 df) .82 (2 dJ) .63 (4 dfl 8 (48%) .19 (1 df) .75 (1 dJ) .30 (2 dfl 4 (23%) .95 (1 df) .86 (1 dJ) .98 (2 dfl 4 (23%) .20 (1 dfl .54 (1 dfl .29 (2 df) ing second fetuses were delivered spontaneously or by outlet forceps regardless of the interval. The 11 total breech extractions occurred within the first 15 minutes, in contrast to spontaneous or assisted extraction of the other 34 breech fetuses, which often occurred in a less hurried manner. Extensive lacerations of the cervix or vagina, halo­thane anesthesia for delivery of the second twin, retained placental fragments requiring reexploration, and postpartum anemia requiring transfusion were uncommon and not more frequent in patients deliver­ing the second twin vaginally after the initial 15 min­utes. Combined vaginal-abdominal delivery in ten of the 115 (9%) cases was significantly more common after the initial 15 minutes (eight of 45 verus two of 70, P < .02). Indications for cesarean section included failed version and extraction of a fetus with a trans­verse or oblique lie (five), prolapsed umbilical cord (four), and failure to progress with fetal distress (one). All the infants survived. No second infant had an obvious major malformation or sign of excess trauma at birth. Apgar scores of the second twin were general­ly high regardless of the interval between deliveries, Table 3. Relationship Between Mode of Delivery of the Second Twin and Interval Between Vaginal Deliveries of Twins in Pregnancies (N = 105) Interval <15 min 16-30 min >30 min Mode of vaginal delivery (N = 68) (N = 23) (N = 14) Cephalic Spontaneous 3.7 (54%) 18 (78%) 11 (79'*,) Outlet forceps 2 (3%) 2 (9%) 1 (7%) Midforceps 0 0 0 Breech Spontaneous 3 (4%) 1 (4%) 1 (7%) Assisted extraction 15 (22%) 2 (9%) 1 (7%) Total extraction 11 (16%) 0 0 Obstetrics & Gynecology t f j I I and ,\'ere usually similar ( Apgar scmes. All 17 seCi 30 minutes had five-mir and 10. The birth weight! remarkably lower or hig roce) tha~ the first hvl.I r;reater than 15 minutes ~ };eonatal complicatio were uncommon regal ffi5titution. Morbid COrl.( maturity (respiratory I dice) but also included, n~ for intensive carE quent and no more CI delivering long after t1 admissions to the inter irequent in the second d the intervat betwee \ The longest interde \'o!ved a 31-year-old 1 \\hose twin gestatio gestation by ultraso\ gestation the patien because of mild prel maturity was confirr amniotomy was pe proceeded unevent female with Apgar minutes, respective1 the vaginal route. l to be in cephalic pn the cervix had retr<l continued. When I1 after the next 15 I was beguI1. Uterir dilated gradually. dilated, the patien head descended 1 I 1 { l ( t ( 1 \ r r Apgar scores of respectively, was parium course '\v, Discussion The authors COl determine whet twin ,.,'as truly 1- monitoring was interval of 21 m not much long€ of 17.5 minu tes no perinatal d supports the ( VOL. 63. NO.4, 15 min ; 16-30 nin liS ·30 [llin o (2 d{) )2 (2 dfl l4 (2 dll 53 (4 d{) 30 (2 d{) ;)8 (2 dj) ~ y or by l1 total tinutes, .1 of the n a less 0\, halo­: l. twin, oration, ,n were deliver- 15 min­n ten of :omn1on va of 70, nc1uded a trans­cal cord S5 (one). . had an j trauma general· )livcrics, . of the ina] 1(5) _.""--.........- -~- >3() min -(N ,,~- 14) 'J'l (79~) '1 (7%) () 1 (7%) 1 (7%) -() and were usually similar or identical to the first infant's Apgar scores. All 17 second twins delivering beyond 30 minutes had five-minute Apgar scores between 8 and 10. The birth weights of the second twins were not remarkably lower or higher (more than a 200-g differ­ence) than the first twins if the delivery interval was greater than 15 minutes (Table 2). Neonatal complications among the second twins were uncommon regardless of the interval or the institution. Morbid conditions related primarily to pre­maturity (respiratory distress, hypoglycemia, jaun­dice) but also included anemia and possible sepsis. The need for intensive care nursery admission was infre­quent and no more common among second infants delivering long after the first (Table 2). Furthermore, admissions to the intensive care nursery were no more frequent in the second than in the first twin, regardless of the interval between deliveries . The longest interdelivery interval (134 minutes) in­volved a 31-year-old black woman, gravida 2, para I, whose twin gestation was diagnosed at 24 weeks' gestation by ultrasound examination. At 38 weeks' gestation the patient was admitted to the hospital because of mild preeclampsia. After fetal pulmonary maturity was confirmed by amniotic fluid testing, an amniotomy was performed and the induced labor proceeded uneventfully. The first infant, a 2438-g female with Apgar scores of 8 and 8 at one and five minutes, respectively, was delivered spontaneously by the vaginal route. The second infant was determined to be in cephalic presentation at minus one station, but the cervix had retracted to 6 cm. Fetal monitoring was continued. When no uterine contractions were evident after the next 15 minutes, a dilute oxytocin infusion was begun. Uterine activity resumed, and the cervix dilated gradually. Once the cervix was completely dilated, the patient was encouraged to push. The fetal head descended well, and a 2500-g male infant with Apgar scores of 8 and 9 at one and five minutes, respectively, was delivered spontaneously. The post­partum course was uncomplicated . Discussion The authors considered the interdelivety interval to determine whether a delay in delivery of the second twin was truly hazardous when close fetal and uterine monitoring was employed. The average interdelivery interval of 21 minutes (range, one to 134 minutes) was not much longer than that reported by Jouppila et al l6 of17.5 minutes (range, zero to 92 minutes). There were no perinatal deaths in the study population, which supports the contention by Jouppila et a116 that the VOL. 63, NO.4, APRIL 1984 interdelivery interval does not have any significant effect on the perinatal mortality of second twins. In the present authors' experience, perinatal morbid­ity was lowest with expectant therapy and subsequent spontaneous delivery, regardless of the fetal presenta­tion. The availability of portable real-time ultrasonog­raphy during labor and delivery has afforded the obstetrician a means of rapid determination of fetal presentation and of monitoring the fetal heart rate and localizing the umbilical cord of the second twin. Accu­mulated experience with electronic monitoring now facilitates the assessment of fetal status and uterine activity. Placental separation while awaiting delivery of the second twin is a theoretic concern because of the rapid reduction of volume in the intrauterine contents. Although excessive vaginal bleeding is uncommon, a search must be undertaken after delivery of the first twin. Unless labor has resumed within ten minutes, oxytocin augmentation of labor is recommended as the fetal heart rate is monitored electronicallyY An initial 5- to lO-mUlminute dose has been used if mild or infrequent contractions are present. Once the present­ing fetal part is in the pelvic inlet, amniotomy is recommended while the presenting part is guided further into the pelvis. Vaginal delivery of the first twin does not guarantee a safe vaginal delivery of the second twin. Occasional­ly, delivery of the second twin by cesarean section may become necessary because of the complications de­scribed here and in prior studies. The frequency of vaginal-abdominal deliveries varied at each institution in the study, but the overall rate (9%) was higher than the 0.001 to 2% reported elsewhere.5 ,23.24 An explana­tion for this discrepancy may involve changes in atti­tudes toward fetal monitoring and neonatal care and limitations or experiences of the attending physicians. Although there is an increased inCidence of malpre­sentation among second twins, which requires more operative deliveries, the authors' impressions are the same as those of Acker et al25 that vaginal delivery may be considered when the second twin is in a breech presentation. An immediate breech extraction or cesar­ean section does not need to be performed routinely for the delivery of the second twin if it is in a trans­verse, oblique, or high breech presentation. Instead, mirtimal interference during close monitoring and se­lective cesarean section for a malpresenting second twin may lead to a more favorable outcome for the mother and fetus. 26 Any intrauterine manipulation or external version of a breech fetus is optimal when assisted by real-time ultrasonography to visualize the operator's hand in relation to the fetal extremities.27 The overall favorable outcome of the second twins in the study may be attributed to the care provided to this Rayburn et al Time Intervals in Multiple Gestations 505 select pregnant population. The first twin in each case was in a cephalic presentation and delivered late in gestation at a regional perinatal center with a well­equipped and well-staffed intensive care nursery. Low Apgar scores were not more common among second twins than among first twins. This finding is to be expected if the fetuses are monitored closely as gesta­tional age advances. 2o The usual neonatal disorders in the second twin did not differ significantly from those occurring in the first twin and were not found to be influenced by the interval between delivery of the infants. Cautious observation of twin infants born after 33 weeks' gestation remains necessary, as infection, hemorrhage, hypoglycemia, malformation, and hemo­lytic disease are seen frequently in preterm twin new­born infan ts. 19 References 1. Kauppila A, louppila P, Koivisto M, et al: Twin pregnancy: A clinical study of 335 cases. Acta Obstet Gynecol Scand (Suppl) 54:5, 1975 2. Ferguson WF: Perinatal mortality in multiple gestations: A review of perinatal deaths from 1609 multiple gestations. Obstet Gyneeol 23:861, 1964 3. Farooqui MO, Grossman JH, Shannon RA: A review of twin pregnancy and perinatal mortality. Obstet Gynecol Surv 28:144, 1973 4. Ware HH: The second twin. Am J Obstet GynecolllO:865, 1971 5. Guttmacher AF, Kohl SG: Cesarean section in twin pregnancy. Am J Obstet Gynecol 83:866, 1962 6. Collea JV: Twins, Protocols for High-Risk Pregnancies. Edited by JT Queenan, JC Hobbins. Oradell, NJ, Medical Economics, 1982, pp 284-285 7. Barrett JM, Staggs SM, VanHooydonkJE, et al: The effect of type of delivery upon neonatal outcome in premature twins. Am I Obstet Gynecol 143:360, 1982 8. Quilligan EJ, Zllspan FP: Douglas-Stromme Operative Obstetrics. Fourth edition. New York, Appleton-Century-Crofts, 1982, pp 667-668 9. Medearis AL, lonas HS, Stockballer JW, et al: Perinatal deaths in twin pregnancy: A five-yenr annlysis of statewide statistics in Missouri. Am J Obstet Gynecol 134:413, 1979 10. McCarthy B}, Sacils [JP, Layde PM, ~t nl: The epidemiology of neonatal dealhs in lwins. Am I Obsl~t Gynecol 141:252, 1981 11. Spurway IH: The fale and m~nilgement of the second twin. Am I Obstel Gynecol 83:1377, 1962 12. Langer H: Perinatale Mortalitiil del' Zwillingsgeburt. Zentrolb Gynaekol 9'1:1288, 1972 13. Ellis JW: Multiple Gestation, A Clinical Manual of Obstetrics. 506 Rayburn et al Time Intervals in Multiple Gestations Edited by JW Ellis, CRB Beckman. Norwalk, CT, Appleton­Century- Crofts, 1983, p 572 14. Falkner F, Hendricks CH: Clinical aspects of twinning, Fetal and Maternal Medicine. Edited by EJ Qllilligan, N Kretcher. New York, Wiley 1980, p 432 15. Oxorn H: Human Birth and Labor. New York, Appleton-Centu­ry- Crofts, 1980, pp 284-285 16. ]ouppila p, Kauppila A, Koivisto M, et al: Twin pregnancy: The role of active management during pregnancy and delivery. Acta Obstet Gynecol Scand (Suppl) 54:13, 1975 17. Koivisto M, Jouppila p, Kauppila A, et al: Twin pregnancy: Neonatal morbidity and mortality. Acla Obstet Gynecol Scand (Suppl) 54:21, 1975 18. Pettersson F, Smedby B, Lindmark G: Outcome of twin birth: Review of 1636 children born in twin birth. Acta Paediatr Scand 65:473, 1976 19. Ho SK, Wu PYK: Perinatal factors and neonatal morbidity in twin pregnancy. Am J Obstet Gynecol 122:979, 1975 20. Cetrulo CL, lngardia C], Sbarra AJ: Management of multiple gestation. Ciin Obstet Gynccol 23:533, 1980 21. Read JA, Miller FC: Technique of simultaneous direct intrauterine pressure recording for electronic monitoring of twin gestation in labor. Am] Obstet GynecoI129:228, 1977 22. Pritchard JA, MacDonald PC: Williams Obstetrics. 16th edition. New York, Applelon-Century-Crofts, 1980, pp 660-661 23. Evrard JR, Gold EM: Cesarean section for delivery of the second twin. Obstet Gyneeol 57:581, 1981 24. Kizer 5, Aguero 0: Cesarean en segundo gemelar. Rev Obstet Ginecol Venez 37:167, 1977 25. Acker D, Lieberman M, Holbrook RH, et al: Delivery of the second twin. Obstet Gynccol 59:710, 1982 26. Kelsick F, Minkoff H: Management of the breech second twin. Am J Obstet Gynecol 144:783, 1982 27. Chervenak FA, lohnson RE, Berkowitz RL, et al: Intrapartum external version of th~ second twin. Obstet Gynecol 66:120, 1983 Address reprint requests to: William F. Raybu1'll, MD Department of Obstetrics and Gynecology Womell'S Hospital The Ulliversihj of Michigan Alln Arbor, MT 48109 Submitted for plI/JIimtioll J!lly11, 1983. Rel'iscd September 26, 1983. Accepted for pu/JIimtioll SeptclIll'er 30, 1983. Copyright © 1984 by The American College of Obstetrici,U1s ilnd Gynecologists. Obstetrics & Gynecology ~latern: t Estradil i in Earl; 1 ~UTH FREE , HAROLD S( 1_,.:".· """,th,16" 'm"Jn\ l~\"el of e;,trial, 2.1 ng/ ~ .1 ' 7~ n~mL .-\m~ , "••, " eti'ni'r,r c2m6e3, 32.53 ;1n.1g h[ llle h,ith p lasl (orrelah- signi 01 es\radio I ar relation,;hip l! ( 1 { l f { ( i I f { d~cidual tisSli ,fa G~mfcal I ~k:dml pI £te~5iYtlv ~::!r-"'.ii01· ~E Fr('>;rc3~ivi -Cl,t :::0urce nDzm:>J prl 3b~2 quanl ch::t;es t centr:itiCf S2eD in n" Tl-,e ad ar~t~;0ni pC<i3.ctin le·r-els. ~ ~ ffi3.tErna .-\!it 11 i 0 t~ ti'}!l. C1 (c.rri:lc_t F"b;:ti ti!3.t br, F, ,''': t,i A'.': E