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A 32 weeks twin pregnancy in a non-communicating rudimentary horn: Case report
Middle East Fertility Society Journal (2012) 17, 290–292
Middle East Fertility Society
Middle East Fertility Society Journal www.mefsjournal.org www.sciencedirect.com
CASE REPORT
A 32 weeks twin pregnancy in a non-communicating rudimentary horn: Case report Mohammed Khairy Ali *, Sherif A. Shazly, Ahmed Y. Abdelbadee, Ali H. Ali Women Health Hospital, Assiut University, Assiut, Egypt Received 17 January 2012; accepted 23 February 2012 Available online 21 April 2012
KEYWORDS Non-communicating rudimentary horn; Pregnancy; Unicornuate uterus
Abstract Introduction: Pregnancy in a rudimentary horn represents a serious implication of this rare uterine anomaly. In 90% of cases, rupture of the horn occurred in the second trimester. In this report, we present a rare case of intact twin pregnancy in a non-communicating rudimentary horn that reached 32 weeks of gestation. Case presentation: A 25 years old Caucasian woman pregnant for 32 weeks presented with shock, acute lower abdominal pain and considerable vaginal bleeding. The patient was shocked and the uterus was tender and tense. Trans-abdominal ultrasound scan revealed a twin intrauterine pregnancy with no cardiac activity in both fetuses, fetal biometry was equivalent to 32 weeks and there was a huge retroplacental hematoma. Urgent laparotomy was performed and a huge intact right sided rudimentary horn was identified. Vertical incision was done with extraction of the dead twins, and the horn was excised. Conclusion: Despite being rare, rudimentary horn pregnancy should be suspected regardless of the gestational age. Placental abruption should also be considered as an unusual presentation of this condition. 2012 Middle East Fertility Society. Production and hosting by Elsevier B.V. All rights reserved.
1. Introduction Mu¨llerian duct anomalies represent an infrequent but serious category encountered in gynecology practice. They result from defective fusion or defective absorption of female reproductive
* Corresponding author. Tel.: +20 1005537951. E-mail address: [email protected] (M.K. Ali). Peer review under responsibility of Middle East Fertility Society.
Production and hosting by Elsevier
system during embryonic life (1). The true prevalence of mu¨llerian duct abnormalities is not well established because a majority of patients are asymptomatic (2). However, the prevalence is approximately 1:200–1:600 in fertile women (3). In spite of being relatively rare, rudimentary horn represents a serious gynecologic condition if it is implicated with pregnancy. Rudimentary horn pregnancy is extremely rare ranging between 1 per 76,000 and 1 per 140,000 pregnancies. Yet, it is associated with high rate of morbidity and mortality as a sequence of rudimentary horn rupture and massive hemoperitoneum (1). In this report, we represent a rare case of intact twin pregnancy in a non-communicating rudimentary horn that reached the 32 weeks of gestation and was presented with placental abruption.
1110-5690 2012 Middle East Fertility Society. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.mefs.2012.02.006
A 32 weeks twin pregnancy in a non-communicating rudimentary horn: Case report
291
2. Case presentation A 25 years old Caucasian gravida 1 Para 0 presented to the emergency unit with severe lower abdominal pain and considerable spontaneous vaginal bleeding that was not preceded by similar attacks. According to her sure reliable dates, the patient was 32 weeks pregnant. Unfortunately, the patient was not regularly followed up during pregnancy; she had a single antenatal care visit in the 5th month of gestation that confirmed her dates and revealed a twin pregnancy. The patient had no significant medical or surgical history and she did not experience any troubles in her first pregnancy. Examination revealed hemodynamic instability; her pulse rate was 120 beats per minute, her blood pressure was 90/60 mmHg and she was severely pale and irritable. The uterus was tender and tense and the fundal level corresponded to the size of 36-week pregnancy. The cervix was soft, 25% effaced and 2.5 cm dilated with severe dark colored vaginal bleeding. A trans-abdominal ultrasound examination was immediately performed. It revealed twin pregnancy with no detected fetal cardiac pulsations in both fetuses. Fetal biometry was equivalent to 32 weeks; the placenta was posterior and high with huge retroplacental hematoma. The patient was diagnosed as 32 week twin pregnancy with placental abruption and the decision of cesarean section was taken for the considerations of her general condition and the severity of vaginal bleeding. Her hemoglobin at the time of admission was 9 g/dl, platelet count was 320 · 109/L, her coagulation profile was normal. Urgent laparotomy revealed a slightly bulky uterus to which a huge intact right rudimentary horn was attached, both tubes and ovaries looked normal (Fig. 1). Vertical incision in the horn was done and the dead monochorionic, monoamniotic male twins were extracted. They looked freshly dead with no apparent fetal anomalies; they weighted about 2050 g for the first fetus and 2200 g for the second. The placenta was delivered and a huge retroplacental hematoma was removed from the horn. Intractable bleeding from the placental bed continued and excision of the horn was mandatory to stop bleeding; the right round and ovarian ligaments were clamped, cut and ligated with Vicryl 2–0 then the horn and the right Fallopian tube were excised (Fig. 2). There was no communication between the rudimentary horn and the main uterine cavity and the stump was sutured in two layers using 2–0 chromic gut
Figure 2
Figure 3
Sectioned rudimentary horn.
View of normal uterus after horn excision.
sutures (Fig. 3). The estimated blood loss was 950 ml. The patient received 3 units of whole blood and 1 unit of fresh frozen plasma intra-operatively. The patient was admitted to the intensive care unit for 12 h for observation. Her postoperative recovery was rapid and uneventful. Her pulse was 88 beat/min, her blood pressure was 110/75 mmHg and her hemoglobin was 10.8 g/dl on postoperative day five. Before discharge, she was counseled on family planning and was educated on the need for antenatal care and elective cesarean section for future pregnancy. 3. Discussion
Figure 1 Intra-operative photograph showing the anterior view of the uterus with the rudimentary horn attached to its right superior border.
Pregnancy in a non-communicating rudimentary horn is a rare but serious complication of mu¨llerian duct anomalies; it is thought to be a result of trans-peritoneal migration of the ovum or the zygote, however, the corpus luteum is observed in the contra-lateral side only in 10% cases. Early diagnosis of rudimentary horn pregnancy is challenging; few cases were diagnosed in the first trimester and most of them were asymptomatic or were known to have a uterine abnormality (4–6). Magnetic resonance imaging (MRI) has proven to be a very useful, noninvasive tool for the diagnosis of mu¨llerian abnormalities; however, this expensive modality is resorted to only
292 when rudimentary horn pregnancy is suspected either by history or by early suspicious ultrasound examination (7,8). First trimester diagnosis of rudimentary horn pregnancy facilitates laparoscopic management. However, Nahum reported uterine rupture in 80% of rudimentary horn pregnancy (9) and most of these cases rupture before the 20th week of gestation (10). Late and false diagnosis with subsequent uterine rupture has been reported repeatedly in many cases (11–13). Others were diagnosed only after an attempt to evacuate the uterus for the termination of an incorrectly diagnosed intrauterine pregnancy (14–16). In this report, we represent a case of rudimentary horn pregnancy that was incorrectly diagnosed prior to laparotomy. However, there are many interesting points to discuss in this case. First: to our knowledge, there were no reported cases of twin pregnancy with both fetuses inside the horn; rudimentary horn twin pregnancy was reported in patients who have one fetus inside the horn and the other inside the uterine cavity (17). The twins reported were monochorionic–monoamniotic and accordingly, cleavage of the fertilized ovum might occur after trans-peritoneal migration of the zygote. Second: the patient was presented by placental abruption with subsequent recent intra-uterine fetal death and shock, this represents an interesting presentation of the case that is commonly presented by uterine rupture or diagnosed during early ultrasound scan in asymptomatic women (1,18), placental abruption is considered ‘‘unusual’’ because rudimentary horn pregnancy is usually associated with pathologic placentation leading to placenta accreta rather than placental separation. This is because the endometrium of the horn is described to be thinner than the usual (19,20). Unfortunately, there was no clue for the actual diagnosis regarding the patient medical or obstetric history and no ultrasound in early pregnancy was reported. With the exception of few reported cases, urgent laparotomy and immediate removal of the horn are a mandatory life saving procedures as in our case (11). The role of laparoscopic resection is limited to pre-rupture first trimester cases and it was reported to be successful in some recent case reports; the procedure can still be converted into laparotomy in spite of these limited indications and this can be attributed to the size and massive vascularity of the pregnant horn (1). 4. Conclusion In this report, we represent a rare case of rudimentary horn pregnancy that was unusually presented by placental abruption. The occurrence of twin pregnancy in a non-communicating rudimentary horn is another interesting finding that needs further evaluation. We also emphasize that the diagnosis of these rare cases should be considered regardless of the gestational age. Management with rudimentary horn excision remains the gold standard method to save the patient. References (1) Tsafrir A et al.. Rudimentary horn pregnancy: first-trimester prerupture sonographic diagnosis and confirmation by magnetic resonance imaging. J Ultrasound Med 2005;24(2):219–23.
M.K. Ali et al. (2) Bhattacharya TK, Sengupta P. Rudimentary horn pregnancy. MJAFI 2005;61:377–8. (3) Tufail A, Hashmi HA. Ruptured ectopic pregnancy in rudimentary horn of the uterus. J Coll Physicians Surg Pak 2007;17(2):105–6. (4) Daskalakis G, Pilalis A, Lykeridou K, Antsaklis A. Rupture of noncommunicating rudimentary uterine horn pregnancy. Obstet Gynecol 2002;100:1108–10. (5) Yahata T, Kurabayashi T, Ueda H, Kodama S, Chihara T, Tanaka K. Laparoscopic management of rudimentary horn pregnancy: a case report. J Reprod Med 1998;43:223–6. (6) Smolders D, Deckers F, Pouillon M, Vanderheyden T, Vanderheyden J, De Schepper A. Ectopic pregnancy within a rudimentary horn in a case of unicornuate uterus. Eur Radiol 2002;12:121–4. (7) Scarsbrook AF, Moore NR. MRI appearances of mu¨llerian duct abnormalities. Clin Radiol 2003;58:747–54. (8) Marten K, Vosshenrich R, Funke M, Obenauer S, Baum F, Grabbe E. MRI in the evaluation of mu¨llerian duct anomalies. Clin Imaging 2003;27:346–50. (9) Nahum GG. Rudimentary uterine horn pregnancy: the 20thcentury worldwide experience of 588 cases. J Reprod Med 2002;47:151–63. (10) Goel P et al.. Unruptured postdated pregnancy with a live fetus in a noncommunicating rudimentary horn. Indian J Med Sci 2007;61(1):23–7. (11) Daskalakis G, Pilalis A, Lykeridou K, Antsaklis A. Rupture of non communicating rudimentary uterine horn pregnancy. Obstet Gynecol 2002;100:1108–10. (12) Kuscu NK, Lacin S, Kartal O, Koyuncu F. Rupture of rudimentary horn pregnancy at the 15th week of gestation: a case report. Eur J Obstet Gynecol Reprod Biol 2002;102:209–10. (13) Nishi H, Funayama H, Fukumine N, et al.. Rupture of pregnant noncommunicating rudimentary uterine horn with fetal salvage: a case report. Arch Gynecol Obstet 2003;268:224–6. (14) Tsuda H, Fujino Y, Umesaki N, Yamamoto K, Ogita S. Preoperative diagnosis of a rudimentary uterine horn. Eur J Obstet Gynecol Reprod Biol 1994;56:143–5. (15) Yoo EH, Chun SH, Woo BH. Laparoscopic resection of a rudimentary horn pregnancy. Acta Obstet Gynecol Scand 1999;78:167–8. (16) Edelman AB, Jensen JT, Lee DM, Nichols MD. Successful medical abortion of a pregnancy within a noncommunicating rudimentary uterine horn. Am J Obstet Gynecol 2003;189:886–7. (17) Shin JW, Kim HJ. Case of live birth in a non-communicating rudimentary horn pregnancy. J Obstet Gynaecol Res 2005;31:329–31. (18) Jayasinghe Y, Rane A, Stalewski H, Grover S. The presentation and early diagnosis of the rudimentary uterine horn. Obstet Gynecol 2005 Jun;105(6):1456–67. (19) Oral B, Guney M, Ozsoy M, Sonal S. Placenta accreta associated with a ruptured pregnant rudimentary uterine horn: case report and review of the literature. Arch Gynecol Obstet 2001;265:100–2. (20) Gagnon AL, Galerneau F, Williams K. Twin pregnancy with one fetus in a rudimentary horn: a case report of a surviving twin. Br J Obstet Gynaecol 1998;105:1326–8.
Middle East Fertility Society
Middle East Fertility Society Journal www.mefsjournal.org www.sciencedirect.com
CASE REPORT
A 32 weeks twin pregnancy in a non-communicating rudimentary horn: Case report Mohammed Khairy Ali *, Sherif A. Shazly, Ahmed Y. Abdelbadee, Ali H. Ali Women Health Hospital, Assiut University, Assiut, Egypt Received 17 January 2012; accepted 23 February 2012 Available online 21 April 2012
KEYWORDS Non-communicating rudimentary horn; Pregnancy; Unicornuate uterus
Abstract Introduction: Pregnancy in a rudimentary horn represents a serious implication of this rare uterine anomaly. In 90% of cases, rupture of the horn occurred in the second trimester. In this report, we present a rare case of intact twin pregnancy in a non-communicating rudimentary horn that reached 32 weeks of gestation. Case presentation: A 25 years old Caucasian woman pregnant for 32 weeks presented with shock, acute lower abdominal pain and considerable vaginal bleeding. The patient was shocked and the uterus was tender and tense. Trans-abdominal ultrasound scan revealed a twin intrauterine pregnancy with no cardiac activity in both fetuses, fetal biometry was equivalent to 32 weeks and there was a huge retroplacental hematoma. Urgent laparotomy was performed and a huge intact right sided rudimentary horn was identified. Vertical incision was done with extraction of the dead twins, and the horn was excised. Conclusion: Despite being rare, rudimentary horn pregnancy should be suspected regardless of the gestational age. Placental abruption should also be considered as an unusual presentation of this condition. 2012 Middle East Fertility Society. Production and hosting by Elsevier B.V. All rights reserved.
1. Introduction Mu¨llerian duct anomalies represent an infrequent but serious category encountered in gynecology practice. They result from defective fusion or defective absorption of female reproductive
* Corresponding author. Tel.: +20 1005537951. E-mail address: [email protected] (M.K. Ali). Peer review under responsibility of Middle East Fertility Society.
Production and hosting by Elsevier
system during embryonic life (1). The true prevalence of mu¨llerian duct abnormalities is not well established because a majority of patients are asymptomatic (2). However, the prevalence is approximately 1:200–1:600 in fertile women (3). In spite of being relatively rare, rudimentary horn represents a serious gynecologic condition if it is implicated with pregnancy. Rudimentary horn pregnancy is extremely rare ranging between 1 per 76,000 and 1 per 140,000 pregnancies. Yet, it is associated with high rate of morbidity and mortality as a sequence of rudimentary horn rupture and massive hemoperitoneum (1). In this report, we represent a rare case of intact twin pregnancy in a non-communicating rudimentary horn that reached the 32 weeks of gestation and was presented with placental abruption.
1110-5690 2012 Middle East Fertility Society. Production and hosting by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.mefs.2012.02.006
A 32 weeks twin pregnancy in a non-communicating rudimentary horn: Case report
291
2. Case presentation A 25 years old Caucasian gravida 1 Para 0 presented to the emergency unit with severe lower abdominal pain and considerable spontaneous vaginal bleeding that was not preceded by similar attacks. According to her sure reliable dates, the patient was 32 weeks pregnant. Unfortunately, the patient was not regularly followed up during pregnancy; she had a single antenatal care visit in the 5th month of gestation that confirmed her dates and revealed a twin pregnancy. The patient had no significant medical or surgical history and she did not experience any troubles in her first pregnancy. Examination revealed hemodynamic instability; her pulse rate was 120 beats per minute, her blood pressure was 90/60 mmHg and she was severely pale and irritable. The uterus was tender and tense and the fundal level corresponded to the size of 36-week pregnancy. The cervix was soft, 25% effaced and 2.5 cm dilated with severe dark colored vaginal bleeding. A trans-abdominal ultrasound examination was immediately performed. It revealed twin pregnancy with no detected fetal cardiac pulsations in both fetuses. Fetal biometry was equivalent to 32 weeks; the placenta was posterior and high with huge retroplacental hematoma. The patient was diagnosed as 32 week twin pregnancy with placental abruption and the decision of cesarean section was taken for the considerations of her general condition and the severity of vaginal bleeding. Her hemoglobin at the time of admission was 9 g/dl, platelet count was 320 · 109/L, her coagulation profile was normal. Urgent laparotomy revealed a slightly bulky uterus to which a huge intact right rudimentary horn was attached, both tubes and ovaries looked normal (Fig. 1). Vertical incision in the horn was done and the dead monochorionic, monoamniotic male twins were extracted. They looked freshly dead with no apparent fetal anomalies; they weighted about 2050 g for the first fetus and 2200 g for the second. The placenta was delivered and a huge retroplacental hematoma was removed from the horn. Intractable bleeding from the placental bed continued and excision of the horn was mandatory to stop bleeding; the right round and ovarian ligaments were clamped, cut and ligated with Vicryl 2–0 then the horn and the right Fallopian tube were excised (Fig. 2). There was no communication between the rudimentary horn and the main uterine cavity and the stump was sutured in two layers using 2–0 chromic gut
Figure 2
Figure 3
Sectioned rudimentary horn.
View of normal uterus after horn excision.
sutures (Fig. 3). The estimated blood loss was 950 ml. The patient received 3 units of whole blood and 1 unit of fresh frozen plasma intra-operatively. The patient was admitted to the intensive care unit for 12 h for observation. Her postoperative recovery was rapid and uneventful. Her pulse was 88 beat/min, her blood pressure was 110/75 mmHg and her hemoglobin was 10.8 g/dl on postoperative day five. Before discharge, she was counseled on family planning and was educated on the need for antenatal care and elective cesarean section for future pregnancy. 3. Discussion
Figure 1 Intra-operative photograph showing the anterior view of the uterus with the rudimentary horn attached to its right superior border.
Pregnancy in a non-communicating rudimentary horn is a rare but serious complication of mu¨llerian duct anomalies; it is thought to be a result of trans-peritoneal migration of the ovum or the zygote, however, the corpus luteum is observed in the contra-lateral side only in 10% cases. Early diagnosis of rudimentary horn pregnancy is challenging; few cases were diagnosed in the first trimester and most of them were asymptomatic or were known to have a uterine abnormality (4–6). Magnetic resonance imaging (MRI) has proven to be a very useful, noninvasive tool for the diagnosis of mu¨llerian abnormalities; however, this expensive modality is resorted to only
292 when rudimentary horn pregnancy is suspected either by history or by early suspicious ultrasound examination (7,8). First trimester diagnosis of rudimentary horn pregnancy facilitates laparoscopic management. However, Nahum reported uterine rupture in 80% of rudimentary horn pregnancy (9) and most of these cases rupture before the 20th week of gestation (10). Late and false diagnosis with subsequent uterine rupture has been reported repeatedly in many cases (11–13). Others were diagnosed only after an attempt to evacuate the uterus for the termination of an incorrectly diagnosed intrauterine pregnancy (14–16). In this report, we represent a case of rudimentary horn pregnancy that was incorrectly diagnosed prior to laparotomy. However, there are many interesting points to discuss in this case. First: to our knowledge, there were no reported cases of twin pregnancy with both fetuses inside the horn; rudimentary horn twin pregnancy was reported in patients who have one fetus inside the horn and the other inside the uterine cavity (17). The twins reported were monochorionic–monoamniotic and accordingly, cleavage of the fertilized ovum might occur after trans-peritoneal migration of the zygote. Second: the patient was presented by placental abruption with subsequent recent intra-uterine fetal death and shock, this represents an interesting presentation of the case that is commonly presented by uterine rupture or diagnosed during early ultrasound scan in asymptomatic women (1,18), placental abruption is considered ‘‘unusual’’ because rudimentary horn pregnancy is usually associated with pathologic placentation leading to placenta accreta rather than placental separation. This is because the endometrium of the horn is described to be thinner than the usual (19,20). Unfortunately, there was no clue for the actual diagnosis regarding the patient medical or obstetric history and no ultrasound in early pregnancy was reported. With the exception of few reported cases, urgent laparotomy and immediate removal of the horn are a mandatory life saving procedures as in our case (11). The role of laparoscopic resection is limited to pre-rupture first trimester cases and it was reported to be successful in some recent case reports; the procedure can still be converted into laparotomy in spite of these limited indications and this can be attributed to the size and massive vascularity of the pregnant horn (1). 4. Conclusion In this report, we represent a rare case of rudimentary horn pregnancy that was unusually presented by placental abruption. The occurrence of twin pregnancy in a non-communicating rudimentary horn is another interesting finding that needs further evaluation. We also emphasize that the diagnosis of these rare cases should be considered regardless of the gestational age. Management with rudimentary horn excision remains the gold standard method to save the patient. References (1) Tsafrir A et al.. Rudimentary horn pregnancy: first-trimester prerupture sonographic diagnosis and confirmation by magnetic resonance imaging. J Ultrasound Med 2005;24(2):219–23.
M.K. Ali et al. (2) Bhattacharya TK, Sengupta P. Rudimentary horn pregnancy. MJAFI 2005;61:377–8. (3) Tufail A, Hashmi HA. Ruptured ectopic pregnancy in rudimentary horn of the uterus. J Coll Physicians Surg Pak 2007;17(2):105–6. (4) Daskalakis G, Pilalis A, Lykeridou K, Antsaklis A. Rupture of noncommunicating rudimentary uterine horn pregnancy. Obstet Gynecol 2002;100:1108–10. (5) Yahata T, Kurabayashi T, Ueda H, Kodama S, Chihara T, Tanaka K. Laparoscopic management of rudimentary horn pregnancy: a case report. J Reprod Med 1998;43:223–6. (6) Smolders D, Deckers F, Pouillon M, Vanderheyden T, Vanderheyden J, De Schepper A. Ectopic pregnancy within a rudimentary horn in a case of unicornuate uterus. Eur Radiol 2002;12:121–4. (7) Scarsbrook AF, Moore NR. MRI appearances of mu¨llerian duct abnormalities. Clin Radiol 2003;58:747–54. (8) Marten K, Vosshenrich R, Funke M, Obenauer S, Baum F, Grabbe E. MRI in the evaluation of mu¨llerian duct anomalies. Clin Imaging 2003;27:346–50. (9) Nahum GG. Rudimentary uterine horn pregnancy: the 20thcentury worldwide experience of 588 cases. J Reprod Med 2002;47:151–63. (10) Goel P et al.. Unruptured postdated pregnancy with a live fetus in a noncommunicating rudimentary horn. Indian J Med Sci 2007;61(1):23–7. (11) Daskalakis G, Pilalis A, Lykeridou K, Antsaklis A. Rupture of non communicating rudimentary uterine horn pregnancy. Obstet Gynecol 2002;100:1108–10. (12) Kuscu NK, Lacin S, Kartal O, Koyuncu F. Rupture of rudimentary horn pregnancy at the 15th week of gestation: a case report. Eur J Obstet Gynecol Reprod Biol 2002;102:209–10. (13) Nishi H, Funayama H, Fukumine N, et al.. Rupture of pregnant noncommunicating rudimentary uterine horn with fetal salvage: a case report. Arch Gynecol Obstet 2003;268:224–6. (14) Tsuda H, Fujino Y, Umesaki N, Yamamoto K, Ogita S. Preoperative diagnosis of a rudimentary uterine horn. Eur J Obstet Gynecol Reprod Biol 1994;56:143–5. (15) Yoo EH, Chun SH, Woo BH. Laparoscopic resection of a rudimentary horn pregnancy. Acta Obstet Gynecol Scand 1999;78:167–8. (16) Edelman AB, Jensen JT, Lee DM, Nichols MD. Successful medical abortion of a pregnancy within a noncommunicating rudimentary uterine horn. Am J Obstet Gynecol 2003;189:886–7. (17) Shin JW, Kim HJ. Case of live birth in a non-communicating rudimentary horn pregnancy. J Obstet Gynaecol Res 2005;31:329–31. (18) Jayasinghe Y, Rane A, Stalewski H, Grover S. The presentation and early diagnosis of the rudimentary uterine horn. Obstet Gynecol 2005 Jun;105(6):1456–67. (19) Oral B, Guney M, Ozsoy M, Sonal S. Placenta accreta associated with a ruptured pregnant rudimentary uterine horn: case report and review of the literature. Arch Gynecol Obstet 2001;265:100–2. (20) Gagnon AL, Galerneau F, Williams K. Twin pregnancy with one fetus in a rudimentary horn: a case report of a surviving twin. Br J Obstet Gynaecol 1998;105:1326–8.