Interstitial pregnancy
Encyclopedia
An interstitial pregnancy is a uterine but ectopic pregnancy
; the pregnancy
is located outside of the uterine cavity in that part of the Fallopian tube
that penetrates the muscular layer of the uterus
. The term cornual pregnancy is sometimes used as a synonym, but remains ambiguous as it is also applied to indicate the presence of a pregnancy located within the cavity in one of the two upper "horns" of a bicornuate uterus
. Interstitial pregnancies have a higher mortality than ectopics in general.
which is connected to both, the uterine
and the ovarian artery
. Surrounded by uterine muscle (myometrium
) it can expand significantly when it hosts a pregnancy.
Interstitial pregnancies can be confused with angular pregnancies; the latter, however, are located within the endometrial cavity in the corner where the tube connects; typically those pregnancies are viable although a high miscarriage has been reported. A pregnancy located next to the interstitial section laterally is an isthmic tubal pregnancy.
The definition of an ectopic pregnancy is a pregnancy outside of the uterine cavity, not outside of the uterus, as the interstitial pregnancy is still a uterine pregnancy.
(hCG) assay. As in other cases of ectopic pregnancy, risk factors are previous tubal pregnancy, IVF therapy, tubal surgery, and a history of sexual infection.
Typical symptoms of an interstitial pregnancy are the classical signs of ectopic pregnancy, namely abdominal pain
and vaginal bleeding
. Hemorrhagic shock is found in almost a quarter of patients.; this explains the relatively high mortality rate.
In pregnant patients sonography is the primary method to make the diagnosis, even when patients have no symptoms. The paucity of myometrium around the gestational sac is diagnostic, while, in contrast, the angular pregnancy has at least 5 mm of myometrium on all of its sides. Ultrasonic criteria for the diagnosis include an empty uterine cavity, a gestational sac
separate from the uterine cavity, and a myometrial thinning of less than 5 mm around the gestational sac; typically the interstitial line sign—an echogenic line from the endometrial cavity to the corner next to the gestational mass—is seen. MRI can be used particularly when it is important to distinguish between an interstitial and angular pregnancy.
On average the gestational age at presentation is about 7–8 weeks. In a 2007 series, 22% of patients presented with rupture and hemorrhagic shock, while a third of the patients were asymptomatic, the remainder had abdominal pain and/or vaginal bleeding. Cases that are not diagnosed until surgery show an asymmetrical bulge in the upper corner of the uterus.
that requires an immediate surgical intervention either by laparoscopy
or laparotomy
to stop the bleeding and remove the pregnancy.
Surgical methods to remove the pregnancy include cornual evacuation, incision of the cornua with removal of the pregnancy (cornuostomy), resection of the cornual area or a cornual wedge resection, typically combined with an ipsilateral salpingectomy
, and hysterectomy
. Because of the vascularity of the interstitial region particularly during pregnancy, blood loss during surgery may be substantial. Postoperatively, patients with conservative surgical therapy are at risk for development of a persistent ectopic pregnancy due to the presence of deeply embedded surviving trophoblast
ic tissue; thus, monitoring of hCG levels is indicated until they become undetectable.
In patients with an asymptomatic interstitial pregnancy methotrexate
has been successfully used, however, this approach may fail and result in cornual rupture of the pregnancy. Selective uterine artery embolization
has been successfully performed to treat interstial pregnancies.
during labor.
Ectopic pregnancy
An ectopic pregnancy, or eccysis , is a complication of pregnancy in which the embryo implants outside the uterine cavity. With rare exceptions, ectopic pregnancies are not viable. Furthermore, they are dangerous for the parent, since internal haemorrhage is a life threatening complication...
; the pregnancy
Pregnancy
Pregnancy refers to the fertilization and development of one or more offspring, known as a fetus or embryo, in a woman's uterus. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets...
is located outside of the uterine cavity in that part of the Fallopian tube
Fallopian tube
The Fallopian tubes, also known as oviducts, uterine tubes, and salpinges are two very fine tubes lined with ciliated epithelia, leading from the ovaries of female mammals into the uterus, via the utero-tubal junction...
that penetrates the muscular layer of the uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
. The term cornual pregnancy is sometimes used as a synonym, but remains ambiguous as it is also applied to indicate the presence of a pregnancy located within the cavity in one of the two upper "horns" of a bicornuate uterus
Bicornuate uterus
A bicornuate uterus or bicornate uterus, commonly referred to as a "heart-shaped" uterus, is a type of uterine malformation where two "horns" form at the upper part of the uterus.-Pathophysiology:A bicornuate uterus is formed during embryogenesis....
. Interstitial pregnancies have a higher mortality than ectopics in general.
Anatomy
The part of the Fallopian tube that is located in the uterine wall and connects the remainder of the tube to the endometrial cavity is called its "interstitial" part, hence the term "interstitial pregnancy"; it has a lenghth of 1–2 cm and a width of 0.7 cm. Its borders are the opening (ostium) of the tube to the endometrial cavity within the uterus and, laterally, the visible narrow segment of the tube. The area is well supplied by the Sampson arterySampson artery
The Sampson artery runs under the round ligament.It represents the anastomosis of the uterine artery and ovarian artery.It is named for John A...
which is connected to both, the uterine
Uterine artery
-Structure:The uterine artery usually arises from the anterior division of the internal iliac artery. It travels to the uterus, crossing the ureter anteriorly, reaching the uterus by traveling in the cardinal ligament....
and the ovarian artery
Ovarian artery
In human anatomy, the ovarian artery is a blood vessel that supplies oxygenated blood to the ovary. It arises from the abdominal aorta below the renal artery, and does not pass out of the abdominal cavity. It can be found in the suspensory ligament of the ovary, anterior to the ovarian vein and...
. Surrounded by uterine muscle (myometrium
Myometrium
The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells , but also of supporting stromal and vascular tissue...
) it can expand significantly when it hosts a pregnancy.
Interstitial pregnancies can be confused with angular pregnancies; the latter, however, are located within the endometrial cavity in the corner where the tube connects; typically those pregnancies are viable although a high miscarriage has been reported. A pregnancy located next to the interstitial section laterally is an isthmic tubal pregnancy.
The definition of an ectopic pregnancy is a pregnancy outside of the uterine cavity, not outside of the uterus, as the interstitial pregnancy is still a uterine pregnancy.
Frequency
Interstitial pregnancies account for 2–4% of all tubal pregnancies, or for 1 in 2,500 to 5,000 live births. About one in fifty women with an interstitial pregnancy dies. Patients with an interstitial pregnancies have a 7-times higher mortality than those with ectopics in general. With the growing use of assisted reproductive technologies, the incidence of interstitial pregnancy is rising.Diagnosis
Early diagnosis is important and today facilitated by the use of sonography and the quantitative human chorionic gonadotropinHuman chorionic gonadotropin
Human chorionic gonadotropin or human chorionic gonadotrophin is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast .. Some tumors make this hormone; measured elevated levels when the patient is not...
(hCG) assay. As in other cases of ectopic pregnancy, risk factors are previous tubal pregnancy, IVF therapy, tubal surgery, and a history of sexual infection.
Typical symptoms of an interstitial pregnancy are the classical signs of ectopic pregnancy, namely abdominal pain
Abdominal pain
Abdominal pain can be one of the symptoms associated with transient disorders or serious disease. Making a definitive diagnosis of the cause of abdominal pain can be difficult, because many diseases can result in this symptom. Abdominal pain is a common problem...
and vaginal bleeding
Vaginal bleeding
Vaginal bleeding refers to bleeding in females that is either a physiologic response during the non-conceptional menstrual cycle or caused by hormonal or organic problems of the reproductive system. Vaginal bleeding may occur at any age, but always needs investigation when encountered in female...
. Hemorrhagic shock is found in almost a quarter of patients.; this explains the relatively high mortality rate.
In pregnant patients sonography is the primary method to make the diagnosis, even when patients have no symptoms. The paucity of myometrium around the gestational sac is diagnostic, while, in contrast, the angular pregnancy has at least 5 mm of myometrium on all of its sides. Ultrasonic criteria for the diagnosis include an empty uterine cavity, a gestational sac
Gestational sac
The gestational sac is the only available intrauterine structure that can be used to determine if an intrauterine pregnancy exists, until the embryo is identified....
separate from the uterine cavity, and a myometrial thinning of less than 5 mm around the gestational sac; typically the interstitial line sign—an echogenic line from the endometrial cavity to the corner next to the gestational mass—is seen. MRI can be used particularly when it is important to distinguish between an interstitial and angular pregnancy.
On average the gestational age at presentation is about 7–8 weeks. In a 2007 series, 22% of patients presented with rupture and hemorrhagic shock, while a third of the patients were asymptomatic, the remainder had abdominal pain and/or vaginal bleeding. Cases that are not diagnosed until surgery show an asymmetrical bulge in the upper corner of the uterus.
Treatment
Choice of treatment is largely dictated by the clinical situation. A ruptured interstitial pregnancy is a medical emergencyMedical emergency
A medical emergency is an injury or illness that is acute and poses an immediate risk to a person's life or long term health. These emergencies may require assistance from another person, who should ideally be suitably qualified to do so, although some of these emergencies can be dealt with by the...
that requires an immediate surgical intervention either by laparoscopy
Laparoscopy
Laparoscopy is an operation performed in the abdomen or pelvis through small incisions with the aid of a camera...
or laparotomy
Laparotomy
A laparotomy is a surgical procedure involving a large incision through the abdominal wall to gain access into the abdominal cavity. It is also known as coeliotomy.- Terminology :...
to stop the bleeding and remove the pregnancy.
Surgical methods to remove the pregnancy include cornual evacuation, incision of the cornua with removal of the pregnancy (cornuostomy), resection of the cornual area or a cornual wedge resection, typically combined with an ipsilateral salpingectomy
Salpingectomy
Salpingectomy refers to the surgical removal of a Fallopian tube.-Indications:The procedure was first performed by Lawson Tait in patients with a bleeding ectopic pregnancy; this procedure has since saved the lives of countless women...
, and hysterectomy
Hysterectomy
A hysterectomy is the surgical removal of the uterus, usually performed by a gynecologist. Hysterectomy may be total or partial...
. Because of the vascularity of the interstitial region particularly during pregnancy, blood loss during surgery may be substantial. Postoperatively, patients with conservative surgical therapy are at risk for development of a persistent ectopic pregnancy due to the presence of deeply embedded surviving trophoblast
Trophoblast
Trophoblasts are cells forming the outer layer of a blastocyst, which provide nutrients to the embryo and develop into a large part of the placenta. They are formed during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg...
ic tissue; thus, monitoring of hCG levels is indicated until they become undetectable.
In patients with an asymptomatic interstitial pregnancy methotrexate
Methotrexate
Methotrexate , abbreviated MTX and formerly known as amethopterin, is an antimetabolite and antifolate drug. It is used in treatment of cancer, autoimmune diseases, ectopic pregnancy, and for the induction of medical abortions. It acts by inhibiting the metabolism of folic acid. Methotrexate...
has been successfully used, however, this approach may fail and result in cornual rupture of the pregnancy. Selective uterine artery embolization
Uterine artery embolization
Uterine artery embolization is a procedure where an interventional radiologist uses a catheter to deliver small particles that block the blood supply to the uterine body...
has been successfully performed to treat interstial pregnancies.
Subsequent pregnancies
Patients with an ectopic pregnancy are generally at higher risk for a recurrence, however, there are no specific data for patients with an interstitial pregnancy. When a new pregnancy is diagnosed it is important to monitor the pregnancy by transvaginal sonography to assure that is it properly located, and that the surgically repaired area remains intact. Cesarean delivery is recommended to avoid uterine ruptureUterine rupture
Uterine rupture is a potentially catastrophic event during childbirth by which the integrity of the myometrial wall is breached. In an incomplete rupture the peritoneum is still intact. With a complete rupture the contents of the uterus may spill into the peritoneal cavity or the broad ligament...
during labor.