What does müllerian mean and what causes these anomalies?

What does müllerian mean?
The uterus, fallopian tubes and upper vagina are made up of two partially fused tubes, which, in the embryo, are known as müllerian ducts, named for physiologist Johannes Peter Müller, who first described them in 1830. They are also known as the paramesonephric ducts, and are at first present in embryos of both sexes.

Normally, these ducts run down vertically from flank to pelvic floor in the young embryo and eventually fuse into a double-barreled tube with two loose ends, known as the uterovaginal primordium, or UVP. The double UVP will eventually merge into a single-barreled uterus, cervix and upper vagina, while the loose ends develop into the fallopian tubes. In adulthood, these organs are referred to as the müllerian tract and congenital malformations of this tract are called müllerian anomalies, or MAs.

In the male embryo, in the presence of anti-müllerian hormone (AMH), the müllerian structures disintegrate during early development. They persist in the female because she does not produce AMH.

In the embryo, the müllerian ducts act as scaffolding for the mesonephric ducts, which give rise to the kidneys. Because of this parallel structural relationship, it is common for a kidney or other urinary anomaly to be present with a müllerian anomaly.

What causes müllerian anomalies?
To date, there is no singular cause for müllerian anomalies. Some may be hereditary , others result from an insult to the fetus while in the womb (the T-shaped uterus of fetuses exposed to DES, for example), and still others may be attributed to random mutation. It is important to remember that in our grandmothers and mothers’ generations, many women with this problem were not diagnosed; while up to 4% of women may have a müllerian anomaly, it may be far more common than physicians realize. Only as diagnostic technology improves and women become more aware of their reproductive health will science get a better understanding as to how common these differences really are. In future years, our honest communication with our children will help build a larger base for understanding the causes of this uniqueness.

What are the different types of müllerian anomalies?

a. Agenesis & hypoplasia: Mayer-Rokitansky-Kuster-Hauser syndrome is most common. All or part of the müllerian tract fails to form, or is extremely underdeveloped. For example, a cervix may be a tissue-thin membrane rather than a tough, fibrous "donut" several centimeters thick. Most women suffering from agenesis or extreme hypoplasia have severe fertility problems, simply by lacking sufficient tissue to support a growing pregnancy. A common diagnosis used to be "infantile uterus," but it simply means a smaller-than-average uterus and does not refer to the MA described above. The old "infantile uterus" is typically capable of supporting a pregnancy very well, since a uterus easily grows during pregnancy. The "infantile" term has fallen by the wayside in recent years.

b. Unicornuate uterus (UU): When one müllerian duct is underdeveloped or fails to develop, a banana-shaped half-uterus is formed. It may or may not be accompanied by a rudimentary horn, and that other horn may or may not have an endometrial cavity or communicate with the main uterine cavity. A missing kidney or other kidney problems accompany this asymmetric anomaly more than they do other MAs. Frequently, the ovary on the rudimentary side is found in an odd place, further up by the ribs. Adverse pregnancy outcomes are common with UU. SEE FIGURE BELOW.

Unicornuate uterus

c. Uterus didelphys (UD): The müllerian tract fails to fuse along all or most of its length. There may be complete duplication of the vagina, cervix and uterus, and the two halves may be divided by a ligament of connective tissue. UD is reported to have the best pregnancy outcomes of all the MAs. SEE IMAGE BELOW.

Uterus didelphys

d. Bicornuate uterus (BU): The uterine fundus fails to fuse and a myometrial division extends down to the cervix in a complete bicornuate uterus, or part way to the cervix in a partial bicornuate uterus. The division is visible on the outside of the uterus, evidenced by a groove or cleft in the uterine dome exceeding 1.5 centimeters. Cervix and vagina are usually single but may be septate or duplicate. BU has relatively few pregnancy complications when compared to SU or UU, with breech presentation being one of the most common. SEE IMAGE BELOW.

Bicornuate uterus

e. Septate uterus (SU): The müllerian tract has fused properly and the uterus looks single from the outside, but the inner duct wall (i.e. the median septum) has failed to dissolve around 20 weeks of gestation, and the uterus retains a double cavity. There may or may not be a shallow groove of 1.5 centimeters or less on the outer uterine dome, and sometimes even a whitish triangle of tissue, the septum itself, is visible. The somewhat fibrous inner septum extends to the internal cervical opening or beyond in a complete septate uterus, and extends only part of the way down in a partial septate or subseptate uterus. The inadequate blood supply and progesterone receptors of the median septum may cause problems in pregnancy, giving the SU the worst pregnancy outcomes of all the MAs. SEE IMAGE BELOW.

Septate uterus

f. Arcuate uterus (AU): The fundus of the uterus may be indented slightly both inside and outside. This shape has been variously defined as slightly bicornuate and slightly septate (and may be either one), and is so slight that it is considered a variation of normal. However, a few studies suggest that increased incidence of adverse pregnancy outcomes are associated with an arcuate uterus.

g. DES-related uterus: A T-shaped uterine cavity, dilated horns and malformed cervix and upper vagina may characterize this anomaly. Unlike the other anomalies, a T-shaped uterus is sometimes caused by maternal ingestion of DES, although sometimes the cause is unknown. When caused by DES, there are often other problems, such as incompetent cervix, infertility and abnormal tissue in the cervix and vagina. DES use is associated with high rates of female cancers, including cancer of the vagina.

Diagnostic Methods

First of all, in an infertility work-up, a hysterosalpingogram (HSG) should be done to either rule out or assess the presence of a two-chambered uterus, the depth of the division, as well as tubal patency. But an HSG alone cannot differentiate between septate and bicornuate uterus. Misdiagnoses of BU by HSG are very common.
Other methods have better levels of reliability:

• Transvaginal ultrasound is nearly 100% successful in detecting a bifid uterus, but only 80% successful in differentiating between SU and BU. It can be a helpful tool in the diagnostic process, but should not be relied upon alone.
• Three-dimensional ultrasound (3DUS), is 92% accurate in differentiation of BU from SU, according to one 1997 study, but not widely available at the time of this writing. It should not be relied upon alone, with an 8% margin of error.
• MRI - According to two studies done in 1994 and 1995, MRI can reliably differentiate between BU from SU, with an accuracy of 100% in comparison with laparoscopy/hysteroscopy. More recent studies cast some doubt on this. Proceed with caution after an MRI.
• Concurrent laparoscopy and hysteroscopy are considered the "gold standard” of BU/SU differentiation. This test is invasive, but if needed, corrective hysteroscopic metroplasty can be done at the same time.

What are some of the pregnancy complications associated with MA's?

Before reading this list of possible complications, it is important to remember that most babies born to women suffering from MAs encounter none of these problems. These are simply possibilities to keep in mind, and most of them come from the potential poor attachment/blood supply of the placenta, or the lack of space.

a. Miscarriage: Spontaneous abortion is very common, especially with the septate uterus, because of blood flow disruptions and possibly hormonal receptor abnormalities. The normal miscarriage rate for a woman with no fertility or anatomical problems is 20%, or 1 out of 5 pregnancies lost. In the septate uterus, which has the worst pregnancy outcomes, some studies show a miscarriage rate approaching 90%.

b. Incompetent cervix: As many as 20% of anomalous uteri may have additional problems, such as incompetent or weak cervix. Such cervices tend to give way between 16 and 22 weeks’ gestation. A woman with a known MA should ask her OB to check for this possibility. Cerclage—sewing a purse stitch around the cervix to keep it closed—is the most common remedy.

c. Placenta previa: Because of the tight quarters in an abnormal uterus, it is a little more common for the placenta to ride low and cover the inner cervical os. This condition poses a bleeding risk, but may correct itself as the pregnancy advances and the uterus stretches upward.

d. Abruptio placenta: Because of the abnormal configuration, contractions and vasculature within an abnormal uterus, problems with its attachment to the uterine wall may arise.

e. Premature labor: Although no one knows all the causes of premature labor, expansion restrictions may be one reason why an anomalous uterus is more prone to it. Another may be disorganized contractions of the abnormal muscle in a septum.

f. Abnormal fetal lie: Breech position is very common in an abnormally shaped uterus, possibly because there is more room for limbs at the bottom, or because the fetus loses its ability to roll 180° earlier than a fetus in a normal uterus.

g. Intrauterine growth restriction (IUGR): Again, because of the possible placental vascular insufficiency, the fetus may not get all the nutrients it needs, and may be small for dates. One form of IUGR tends to spare the brain, and the fetus, if born prematurely, does quite well despite the small size.

Should I see a regular OB-GYN during pregnancy?
While it should be remembered that many women with uterine anomalies have no trouble at all during pregnancy, one can never go wrong erring on the side of caution. If the MA is a severe one (a deep SU or BU, or any UU), it might be wise to at least consult with a high-risk specialist (perinatologist) early in the pregnancy, or have one co-manage your case along with your OB-GYN. Or you might simply interview your OB-GYN and find out how much MA experience he or she has, what his or her philosophy of care is, and whether or not you feel comfortable with it.

Expect to have your cervix length evaluated (sometimes a cervix weakens when the baby is crowded) and possibly treated with a purse stitch (cerclage) if it begins to open up in the second trimester. You may also expect to be monitored for premature labor, intrauterine growth retardation and abnormal fetal lie during your pregnancy; these pregnancy complications are more common with müllerian anomalies.

A list of Terms and Abbreviations

Müllerian Anomalies: Terms
This is a short list of abbreviations and specialized terms used when discussing Müllerian Anomalies on this site.

• AF: "Aunt Flow" or menstrual period.
• Anlage: The name for the undeveloped or rudimentary müllerian duct.
• Arcuate: AU A variation of normal uterine development in which the top of the uterus has a slight dip. Rarely a problem.
• AU: "Arcuate uterus"
• BD: "Baby-dancing," or sex intended for conception.
• BFN: "Big Fat Negative," on a home pregnancy test. "Fat" may be substituted by the F-word of one's choice.
• Bicollis: Meaning "2 cervices." Many septate, bicornuate and didelphys uteri can have a double cervix. Eg. "uterus bicornis bicollis."
• Bicornuate: BU Meaning "two horns," it describes a uterus with a distinct division (> 1 cm.) visible from the outside, caused by incomplete fusion of the two müllerian ducts. A.k.a. "uterus bicornis."
• BMS: "Baby-making sex"
• BU: See: Bicornuate uterus.
• CC: See: Clomid
• Clomid: Brand name of "clomiphene citrate," an oral fertility drug. A.k.a. CC.
• Cornua: Term for the two horns of a uterus, normally united to form a cavity shaped like an upside-down triangle. The cornua are more separate and pronounced in müllerian anomalies.
• DD: "Dear daughter."
• DES: See: Diethylstilbestrol.
• DH: "Dear husband."
• Diethylstilbestrol: DES. Artificial hormone given to pregnant women in cases of threatened abortion, especially during the 1960s and early 1970s. DES was found to cause many reproductive abnormalities in the fetus, including a small uterus with a T-shaped cavity in the female.
• DS: "Dear son."
• DW: "Dear wife."
• Dysmenorrhea: Painful menstrual cramps. Women with uterine anomalies frequently have painful menstruation, typically from associated endometriosis, outlet obstruction, retrograde menstruation and the disorganized muscle contractions caused by an intrauterine septum.
• hCG: "Human chorionic gonadotropin." This is the hormone made by the embryo's placenta. The pregnancy hormone.
• Hemihysterectomy: Removal of one uterine horn, commonly done for the tiny, undeveloped horn opposite a unicornuate uterus.
• Horn: Common term for the hemi-uterine cavities found in bicornuate and septate uteri.
• HPT: Abbreviation for "home pregnancy test."
• HSC: "See: "Hysteroscopy"
• HSG: See: "Hysterosalpingogram"
• Hypoplastic: Term meaning small, or underdeveloped. The small uterus of a DES daughter is said to be hypoplastic.
• Hysterosalpingogram: The x-ray "dye test" good for showing the shape of the uterine cavity and whether or not the oviducts are open.
• Hysteroscopy: A minimally invasive surgery in which a lighted scope is inserted through the cervix of the uterus. It can be done just to check the uterine cavity ("diagnostic hysteroscopy") or to correct polyps, septa, adhesions, etc. ("operative hysteroscopy"). General anesthesia is used for the latter.
• IC: See: incompetent cervix.
• Incompetent cervix: IC. A condition in which the cervix opens up under the weight of a growing pregnancy, and and very common in women with müllerian anomalies. Sometimes the lack of uterine volume forces open an otherwise normal, competent cervix, but it is also the case that a cervix can be malformed or congenitally weakened, as in the case of DES daughters.
• Intrauterine insemination: Placement of live, washed sperm inside the uterine cavity with a catheter. A.k.a. IUI.
• Intravenous pyelogram: "IVP." This is an x-ray dye test of the kidneys, done in women with müllerian defects, most especially those with asymmetrical defects, such as uterus unicornis. Since the urinary and reproductive tracts form at the same time, it is not unusual for a woman with only one uterine horn to lack a kidney or ureter on the opposing side. Likewise, it is sometimes possible to have a "horseshoe kidney," that is a single large kidney extending from one side to the other, caused, much as a septum is, by the failure of some embryonic structure to deteriorate at the right time.
• IUGR: "Intrauterine growth retardation," a condition common when uterine volume is diminished, in which the fetus does not obtain sufficient nutrition from a rapidly aging placenta and is small for gestational age. The placenta deteriorates more rapidly because it is overly compressed as the pregnancy progresses. IUGR also has other causes, such as autoimmune disorders and diabetes.
• IUI: See: Intrauterine insemination.
• IVP: See: "Intravenous pyelogram"
• Jones & Jones metroplasty: A type of alteration of the uterus done through a laparotomy.
• Lap/hyst: Abbreviation "Laparoscopy/hysteroscopy"—a combination of two operations in which the uterus is inspected inside and out, to determine the extent of the malformation. A lap/hyst is the `gold standard' of diagnoses in differentiating between a septate or bicornuate uterus. It is also commonly done during hysteroscopic septoplasty to monitor the operation and verify whether or not a uterine perforation has occurred in the course of the hysteroscopy.
• Laparoscopy: The inflation of the abdomen with carbon dioxide gas and the insertion of a lighted scope through the navel, through a half-inch incision. Additional incisions for manipulating instruments may be made at the pubic hairline. Laparoscopy may be done to diagnose a uterine anomaly, to operate within the abdomen, or to monitor a hysteroscopic procedure. A laparoscopy is classified as major surgery, but recovery time is considerably shorter than that of a laparotomy. "Keyhole surgery."
• Laparotomy: a surgical incision in the wall of the abdomen large enough to admit conventional surgical instruments.
• MA: See: Müllerian anomaly. A.k.a.: Müllerian duct anomaly.
• Magnetic resonance imaging: MRI A noninvasive test useful in seeing the contours of the uterus and differentiating between a septate and bicornuate uterus.
• Malpresentation: Common in women with decreased uterine volume, malpresentation is the position of a fetus in the uterus such that some other part besides the head will be coming out first. "Breech presentation," in which the feet or buttocks present first, is the most common malpresentation in women with uterine anomalies, and a common reason for birth by c-section.
• M/c: "Miscarriage."
• Metroplasty: A general term for the surgical alteration of the uterus, be it surgery to remove a septum or to unite the two horns of a bicornuate uterus. A subset of metroplasty is septoplasty.
• MDA: Abbreviation for müllerian duct anomaly. a.k.a. müllerian anomaly.
• MRI: See: Magnetic resonance imaging
• Müllerian anomaly: A developmental abnormality of the internal female sex organs resulting from the failure of the müllerian ducts to either fuse and/or resorb properly. Müllerian anomalies include hypoplastic uterus, arcuate uterus, septate uterus, bicornuate uterus, unicornuate uterus, T-shaped (DES) uterus, uterus didelphys, Rokitansky Syndrome, and others.
• Müllerian ducts: Two long tubular structures found in both the male and the female embryo. In the male, these ducts dissolve, but in the female, they unite to form the uterus and oviducts.
• OPK: Abbreviation for the home test kit that predicts ovulation.
• Retrograde menstruation: The reversal of menstrual flow; it goes from within the uterus to the pelvic cavity by way of the Fallopian tubes. It is thought to be one cause of endometriosis, which is more common in women with MAs. Retrograde menstruation is also more common in cases of MA.
• Rokitansky Syndrome: The congenital absence of a uterus and upper vagina—the most severe form of Müllerian defect. Also known as "müllerian agenesis."
• Rudimentary horn: the small, undeveloped horn of a unicornuate, didelphic or bicornuate uterus. A.k.a. anlagen.
• Septate: SU. Adjective describing a uterus with an extra fibrous/muscular band in the middle of its cavity, giving it two horn shaped hemi-uterine cavities. This is the most common müllerian anomaly, and results from the partial or total failure of the wall between the united müllerian ducts to dissolve. A.k.a. "uterus septus." Subcategories of the septate uterus include "total," or "complete," in which the septum involves the cervical canal and even the vagina, and "subseptate," in which the septum's lower end stops short of the cervical canal.
• Septoplasty: Surgery to remove a uterine septum, usually done by operative hysteroscopy.
• Septum: The name for the fibrous wall dividing the cavity of a septate uterus.
• SHG: See: Sonohysterogram
• Sonohysterogram: SHG. Ultrasound of the uterus and its cavity, aided by the distention of the uterine cavity with saline solution.
• SSU: "Subseptate uterus"
• Strassman metroplasty: A type of alteration of the uterus done through a laparotomy.
• SU: See: Septate uterus.
• Subseptate: SSU. A form of septate uterus in which there has been a partial dissolution of the embryonic structure dividing the uterine cavity in two. The septum does not run the full length of the uterus.
• T-shaped uterus: The characteristic shape of the cavity of a uterus affected by diethylstilbestrol.
• Tompkins metroplasty: A type of alteration of the uterus done through a laparotomy.
• TTC: "Trying to conceive"
• UD: See: Uterus didelphys
• Ultrasound: "US." A tool which can reveal the inner and outer contours of solid bodily organs such as the uterus and kidneys. Sometimes useful in distinguishing between septate and bicornuate uteri. Synonymous with "sonogram."
• Unicollis: Term meaning "one cervix." Most müllerian anomalies involve the presence of only one cervix. Two cervices are most commonly associated with uterus didelphys, but not always. E.g.: "uterus didelphys unicollis."
• Unicornuate: UU. An asymmetrical uterine anomaly in which one of the two müllerian ducts has failed to form properly. The hemiuterus is a small, banana-shaped organ frequently accompanied by an anlage, or rudimentary uterine horn or bud, which may or may not have an open endometrial cavity. Pregnancies in the smaller horn almost invariably rupture, and to prevent this, a hemihysterectomy may be recommended. Women with UU usually have bilateral ovaries, and may have an associated kidney anomaly on the side with the anlage.
• US: Abbreviation for "ultrasound."
• Uterus Didelphys: Term for the existence in a woman of two separate hemi-uteri, usually each with its own cervix. Some degree of vaginal duplication may also be present. Literally means "two wombs."
• UU: Abbreviation for unicornuate uterus, a.k.a. "uterus unicornis."
• Vaginoplasty: Any surgery done to alter the shape of the vagina. With some müllerian anomalies, especially UD and total SU, there may be a septum present in the upper end of the vagina.