Over a century after the condition was first reported, there are as of yet no analytical studies on the health of children born to women with a history of AS or even on pregnancies conceived with adhesions present. The only data available in the literature are from isolated case reports.
As mentioned elsewhere, the proportion of births after Asherman’s syndrome treatment (ie. births / total number of women treated) are around 40% across all classifications. Reproductive outcome is correlated with severity at diagnosis, with mild cases having a highest live birth ‘rates’ (‘proportion’ is actually the correct terminology) and severe cases having the lowest live birth proportion.
The risks associated with abnormally invasive placenta (accreta, percreta, increta) and low lying placenta (previa) mainly affect the mother at delivery. These can lead to significant blood loss and emergency hysterectomy. Massive hemorrhaging is a life threatening situation for the mother and requires blood transfusions. Conversely, IUGR, preterm birth and IC present a risk for the fetus.
The majority of gestations following the surgical correction of adhesions are uncomplicated and presumably healthy babies are delivered. This is partly because most women who are able to carry pregnancies have an adhesion free uterus with relatively healthy endometrium while in those with severe endometrial injury (resulting in IUA with or without fibrosis) pregnancy is less likely even after surgery, and any pregnancy achieved would generally miscarry early on.
A retrospective case control study found no difference in pregnancy outcome aside from birthweight in pregnancies with and without IUA (1). It should be noted that case-control studies and in general, retrospective studies are not the most rigorous in terms of evidence. Presumably, the extent, severity and location of uterine adhesions affect the course and outcome of the pregnancy. However, if adhesions are only mild and filmy they can stretch or even divide as the uterus grows with the pregnancy. The latter was described in a case report by Klatsky et al (2) (see cases below). As no two cases of AS are identical, it is difficult to predict the outcome and therefore close monitoring of the pregnancy by a high risk obstetrician is advised for regular screening for potential complications such as cervical incompetence, IUGR, premature labour, invasive placenta, and pre eclampsia. Regular screening will also assist in the detection of fetal abnormalities and potentially improve their management. Home births are not advisable in women with past AS even if the pregnancy appears to be progressing without problems, as invasive placenta may not be detected until the time of delivery and this could lead to serious life threatening situations.
Prematurity and neonatal complications
Most health complications in newborns delivered to women with past (or current) AS would probably be related to prematurity, as women with AS (past or current) are more likely to deliver preterm. Prematurity may be caused by other known complications associated with AS such as IUGR. Depending on the extent of prematurity, such birth defects could include neurological problems (eg. cerebral palsy, apnea of prematurity, retinopathy of prematurity), respiratory problems (eg. respiratory distress syndrome), cardiovascular problems (eg. patent ductus arteriosus), gastrointestinal/metabolic disorders (eg. rickets, inguinal hernia), hematological conditions (eg. jaundice, anemia) and infections (eg. sepsis, UTI). Obviously neonatal mortality is another possible complication of premature birth and generally, the earlier the birth, the more severe the complications. Babies born during the second trimester due to cervical incompetence (as a result of previous cervical dilations associated with the index injury leading to AS and/or surgical correction of AS) are often too young to survive outside the body, and even if they do they will have severe and life long complications.
Effect of IUA during pregnancy: four case reports with different outcomes
It is very important that the uterus is assessed for adhesions after treatment of Asherman’s syndrome before conception is attempted/advised. Adhesions are known to recur in moderate and severe cases, and further surgery may be required. Complications will be increased if pregnancy occurs in the presence of thick adhesions. This is highlighted in the examples from case reports below. Note that the first example is one where the patient underwent endometrial ablation (EA) which is a procedure that mimics very severe AS. It is unclear whether the patient was counseled for the risks of a future pregnancy. Usually both IUA and extensive fibrosis are present. In fibrosis the endometrium is replaced with scar tissue to varying extents (hence it is also known as sclerotic endometrium or ‘unstuck’ Asherman’s syndrome due to the absence of adhesions). This is the most severe form of AS. Fibrosis occurs mainly as a result of thermal energy use in the uterus. Electrosurgery (e.g. resectoscope, laser etc.) also leads to IUA because of damage to the basal endometrium. EA is procedure used to treat abnormally heavy bleeding in which the endometrium is intentionally and irreversibly destroyed using thermal ablation. First reported in 1981, EA has been gaining popularity as a less invasive alternative to hysterectomy. Unfortunately damage may also occur unintentionally when these same instruments are used for other purposes such as the resectioning of uterine fibroids or polyps or the dissection of adhesions during the treatment of Asherman’s syndrome. Instead of having their fertility restored, the patient may end up with more severe adhesions and fibrosis than originally. Therefore mechanical dissection of adhesions may have better outcomes. EA should not be undertaken in women who desire future fertility and they should be informed about potential dangers of pregnancies if they fall pregnant. I have seen doctors on the internet advertizing endometrial ablation reversal in women who wish to conceive after having had the procedure. This practice is highly questionable given the high risk of severe pregnancy complications and the low chance of a live birth after EA. Pregnancy rates following EA are in the vicinity of 0.2-0.7% (3,4) with perinatal mortality reported to be 11.8% (4)
Severe AS from EA and birth defects
1. Mukul and Linn (5) reported amniotic band syndrome (ABS) in a pregnancy following endometrial ablation. The patient had three prior pregnancies and one birth. ABS , also called Amniotic Constriction Band Syndrome, is a set of congenital birth defects believed to be caused by entrapment of fetal parts (usually a limb or digits) in fibrous amniotic bands while in utero. The patient had undergone rollerball EA 7 years earlier without complications. Ultrasonography at 7 weeks revealed evidence of amniotic band syndrome: synechiae (i.e. IUA) were seen in the midquadrant of the uterus, creating amniotic sheets and bands with small compartments. The entire lower uterine segment was empty except for the right leg and a loop of umbilical cord poking through the lower uterine synechia. The fetus was of normal size but with clubbed feet, a distorted spine, and ventriculomegaly.
The patient underwent preterm labour and membranes ruptured at 26 weeks. A male infant was delivered via emergency C-section. An emergency hysterectomy was performed. The infant’s birth defects were described as follows:
“There were positional deformities in the neck, an asymmetric chest, severe scoliosis confirmed by X-ray, bilateral clubbed feet, and very limited movement of all long extremities consistent with arthrogryposis. The right lower extremity was swollen, cyanotic, denuded of skin, and without perfusion or pulses. Areas of significant necrosis on the posterior thigh of the right lower extremity were noted.”
Prognosis was poor and the parents decided to withdraw ventilation support. The infant died 6 hours after delivery.
One theory on the cause of ABS is that it occurs when the inner membrane (amnion) ruptures without injury to the outer membrane (chorion), exposing the fetus to fibrous tissue (bands) from the ruptured amnion which can entangle body parts, leading to congenital abnormalities. Another theory is that vascular disruption occurs. The latter would explain the presence of cleft lip in ABS cases. Either theory could account for its description in women with severe injury to the endometrium. Both IUA and fibrosis resulting from EA would lead to vascular disruption.
Mild to moderate IUA during pregnancy
In the three examples below, patients developed IUA from uterine curettage (i.e. D&C). One case ended in the term birth of a healthy baby while the other two resulted in congenital abnormalities. It appears that the severity of the adhesions affects outcome.
2. Klatsky et al (3) report of a pregnancy complicated by endometrial scarring which ended in a term birth of a healthy infant. The patient, a 39 year old woman, had a history of D&C for therapeutic abortion followed by three miscarriages, the last of which was completed by D&C. An ultrasound at 19 weeks identified a thick band crossing the lower uterine segment with the placenta inserting alongside it. Mullerian fusion anomalies were ruled out. Doppler flow imaging demonstrated flow along the synechia to the overlying placenta. At 25 weeks the patient passed half a cup of bright red blood. An ultrasound revealed a thinning scar with placenta still implanted on both sides and a small subchorionic hematoma. At 31 weeks ultrasound demonstrated a reduced scar with placenta visible on only one side. The patient presented at term with premature rupture of the membranes and a fetus in breech presentation. She underwent cesarean delivery. No uterine anomalies or adhesions were found, presumabley the thin uterine adhesion was evacuated with the placenta. The infant had no morphological abnormalities.
3. Deering et al (6) report a case of head entrapment of a second twin by intrauterine synechiae leading to long term health complications. The 40 year old patient had a history of two uterine curettages (ie. D&C) , one for first trimester miscarriage and a second for menorrhagia. CVS was undertaken during first trimester revealing normal male karyotypes. Diagnostic hysteroscopy and lysis of adhesions was not performed prior to IVF resulting in a twin pregnancy. She presented at 19 weeks for evaluation due to a shortened cervix and pronounced funneling (symptoms of cervical insufficiency). A McDonald cerclage was placed. Ultrasound examination also revealed a moderate sized uterine synechiae wrapped around the neck and placenta of twin B. Twin B was affected by IUGR, weighing less than the third percentile for gestational age. The development of growth restriction and discordance in twin B is thought to result from the combination of the contracted space available for twin B’s head to grow, the compression of the umbilical cord against the fetal neck by the uterine band, and the implantation of the placenta in an abnormal portion of the uterus with a potentially inadequate blood supply.
Cesarean delivery was undertaken at 26 weeks due to fetal distress of twin B and head entrapment. As seen on ultrasonography a thick uterine band was tightly constricting the neck of twin B. The location of the tissue was consistent with the uterine synechia observed on hysterosalpingogram before IVF. Twin A did well and was discharged from the NICU at 3 months. Twin B remained in the NICU until 5 months of age, at which time he was discharged to a longer-term pediatric care facility for continued care. This case demonstrates that significant uterine synechia might result in intrauterine head entrapment, as well as IUGR.
4. Baumler et al (7) report a case of premature birth of an infant with prolonged pulmonary distress syndrome and severe kyphoscoliosis (90 degrees) in a patient with IUA. The patient was 37 years of age with a history of two first trimester miscarriages and evacuation of retained products of conception (ERPC or D&C). Preterm labor occurred at 28 weeks. Midtrimester 2D, 3D and real-time 4D ultrasound revealed a horizontal miduterine separation in the form of an ‘egg-timer’. The uterine cavity was separated in two superimposed cavities. The fetus and the placenta were located in the upper part of the uterus, and the right arm of the fetus and part of the umbilical cord extended in the lower part of the uterus, through an opening in the separating horizontal membrane. The kyphoscoliosis, thought to be due to severe oligoamnios was managed conservatively.
The mother’s operative hysteroscopy carried out 6 months later confirmed both clinically and histologically the presence of a transversal muscular synechia.
The examples above illustrate the importance of diagnosing and removing IUA prior to IVF or conception. Furthermore, thick adhesions restrict the growth of the uterus, possibly increasing pressure on the cervix and leading to CI or preterm labor. The patient in the example above (6) may not even have needed IVF as her fertility problems may have been due to Asherman’s syndrome which could have been surgically corrected and allowed a better pregnancy outcome. Not only are the chances of pregnancy reduced, the health of the mother and infant are compromised as well with the presence of IUA. It is particularly irresponsible to perform IVF in patients without confirming an architecturally normal uterus. There is unfortunately a tendency for some clinicians to believe that IUA are harmless and asymptomatic (3) but this case shows that even a single thick band can have significant repercussions during pregnancy. As all cases are not treatable, in particular more severe ones where there is a tendency for scars to reform and irreversible fibrosis to occur, prevention of AS wherever possible is the best and easiest strategy available.
REFERENCES
1. Ball RH, Buchmeier SE, Longnecker M. Clinical significance of sonographically detected uterine synechiae in pregnant patients. J Ultrasound Med. 1997 Jul;16(7):465-9. Abstract
2. Klatsky PC, Tran ND, Strachowski L. A pregnancy complicated by endometrial scarring. Fertil Steril. 2009 Jun;91(6):2707-8. Epub 2008 Nov 20 Abstract
3. Cook JR, Seman E. Pregnancy following endometrial ablation: case history and literature review. Obstet Gynecol Surv 2003;58:551– 6. Abstract
4. Pugh CP, Crane JM, Hogan TG. Successful intrauterine pregnancy after endometrial ablation. J Am Assoc Gynecol Laparosc 2000;7:391– 4. Abstract
5 Mukul LV, Linn JG. Pregnancy complicated by uterine synechiae after endometrial ablation. Obstet Gynecol. 2005 May;105(5 Pt 2):1179-82. Abstract
6 Deering SH, Heller J, Winkel C, Landy HJ. Intrauterine head entrapment of a second twin by a uterine synechia. Obstet Gynecol. 2003 Oct;102(4):693-5. Abstract
7 Bäumler M, Faure JM, Couture A, Flunker S, Boulot P. Prenatal 3D ultrasound and MRI assessment of horizontal uterine synechia. Prenat Diagn. 2008 Sep;28(9):874-5.
