Prabhu S*, Nayak M**, Mishra N***, Jadhav V****.
( * Senior consultant, ** Senior Resident, *** Head of Department, **** Consultant,
Department of Obstetrics and Gynecology, Bhabha Atomic Research Centre Hospital,
Anushakti Nagar, Mumbai, India.)
Intra-amniotic band-like structures are frequently encountered on obstetric sonography. We present an unusual case of suspected amniotic band on prenatal gray scale sonography which turned out to be an intervening membrane containing vessels connecting two lobes of a bilobed placenta.
Intra-amniotic band-like structures are frequently encountered on obstetric sonography. Differential diagnosis of such structures varies from benign conditions like uterine synechiae to relatively serious amniotic band syndromes which often cause fetal deformities. Correct identification of these entities on prenatal sonography is essential to prognosticate outcome and avoid needless alarming of parenting couples.
We present a case of intervening membrane of a bilobed placenta, misdiagnosed as amniotic band on sonography.
Thirty three years old G2, A1, 28 week pregnant; reported to antenatal OPD with fetal echocardiography incidentally showing amniotic band. Patient had a 1st trimester spontaneous incomplete abortion 5 years ago with check curettage. Following which she had secondary infertility with regular menstrual cycles, and on evaluation by diagnostic hystero-laparoscopy had normal findings. After two months, patient conceived spontaneously. Medical history was not contributory. Clinical examination revealed 28 weeks live breech. Antenatal investigations showed normal haemogram, plasma sugar levels and urine examination. Serological tests like HCV, HbSAg, HIV and VDRL were non-reactive.
Figure 1. Two D Sonography (Arrow showing amniotic band).
Gray scale sonography (Figure 1) documented amniotic band arising from lower edge of placenta towards right. No fetal anomalies were detected. Previous sonography reports at 14 and 19 weeks were normal. Level II scan was performed at 19 weeks of gestation which was reported normal i.e. did not show any evidence of amniotic band-like structure. The band was incidentally noted for the first time at the time of fetal echocardiography which was performed at 28 weeks of gestation. The amniotic band was arising from the lower edge of the placenta towards right of the uterus ( not attached to any fetal structures ) and was not associated with any fetal anomalies hence 3 dimensional ultra sound scan or MRI was not advised. Due to the presence of an amniotic band possibility of fetal deformities or antepartum hemorrhage was explained to the couple.
At 35 weeks patient presented with history of premature rupture of membranes with breech presentation. Emergency LSCS was performed under spinal anesthesia. She delivered a 2.25 kg male child with no evidence of deformities and an APGAR of 9/10. Intraoperative findings did not document presence of amniotic band. At LSCS, after baby delivery there was no spontaneous separation of placenta in spite of oxytocics hence a manual separation of placenta was done. The placenta was bilobed (Figure 2) with one lobe at the fundus and the other in the right cornua.
Figure 2. Bilobed Placenta (Arrow showing intervening membrane).
One lobe measured 13 x 11 x 1.7 cm and other 12 x 10 x 1.5 cm. Total weight of the placenta was 760 gm. The umbilical cord measured 56 cm and was inserted on one lobe eccentrically. Two lobes were connected by the intervening membrane through which three connecting vessels were running. Uterine atony was managed conservatively with oxytocic agents.
In our case, intra-amniotic band-like structure was interpreted as amniotic band on pre-natal ultrasound. As amniotic band can lead to fetal deformities, couple was counseled accordingly. On evaluating the outcome of this case, one realizes that this alarming counseling was needless and had created undue anxiety in the couple.
Clinician should keep in mind; true amniotic band is a relatively rare entity. Incidence varies between 1:1200 and 1:15000 live births. Amniotic bands can be formed due to amniotic disruption before 12 weeks of gestation resulting in formation of mesoblastic fibrous strings. They can entrap fetal developing parts causing immobilization, constriction or amputations. Presence of amniotic band is unlikely, especially when no fetal deformities are noted on prenatal scan. On color Doppler examination these bands are avascular hence can be differentiated from other band like structures like synechiae or placental variations. On reviewing literature, Hiromitsu et al have reported a case of large succenturiate lobe of placenta which appeared as amniotic band on gray scale sonography; evaluation by color Doppler revealed fetal blood flow through the membrane connecting two lobes. This helped in differentiating it from amniotic band. Similarly in our case, color Doppler that was unfortunately not done could have helped in diagnosis and to differentiate from amniotic band.
Incidence of bilobed placenta is approximately 1 in 350 deliveries. Rarely, the placenta forms two separate disks of near equal size. The umbilical cord inserts between the two placental lobes either into a connecting chorionic bridge or into intervening membranes. This condition is termed bilobed/ bipartite placenta or placenta duplex. In succenturiate placenta one lobe is smaller than the other. In our case, placenta was bilobed as it had two separate disks of almost equal size.
Usually accessory lobe developed in the membranes has vascular connections of fetal origin. It is important to establish the location of these connecting vessels, and in particular to look for unsupported vascular connection overlying the cervix (vasa previa). This may cause dangerous fetal hemorrhage at delivery. In our case, as the placentation and intervening membrane was on the upper segment and there was no evidence of vasa previa and the neonatal outcome was unaffected.
Other possible complication due to succenturiate/ bilobed placenta is retention of accessory lobe after delivery causing serious post-partum hemorrhage. At LSCS, spontaneous expulsion of placenta did not occur in our patient therefore it was separated manually. Minimal uterine atony that occurred can be contributed to large surface of the placenta. It was controlled with oxytocic agents.
To conclude, precise prenatal diagnosis of intra-amniotic band like structures is essential to avoid undue anxiety in parents and for the clinician to be prepared for associated complications and management to ensure good maternal and fetal outcome.
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Prabhu S, Nayak M, Mishra N, Jadhav V. Is it always an amniotic band? JPGO 2016. Volume 3 No. 2. Available from: http://www.jpgo.org/2016/02/is-it-always-amniotic-band.html