An ectopic pregnancy is one in which the
fertilized ovum is implanted and develops outside the
uterine cavity.
The normal position for a fertilized ovum to implant and grow is inside the uterine cavity. (see How Pregnancy Occurs).
In a normal pregnancy, the growing fetus can be carried to full term inside the uterus since the muscles of the uterus are capable of increasing in size and number.
But, if the embryo is implanted in or on an organ that cannot increase in size, like the fallopian tubes or the ovaries, it fails to develop properly.
Severe bleeding can occur if the tubes rupture at the site of implantation.
SITES OF IMPLANTATION OF ECTOPIC PREGNANCY
- Fallopian Tubes: The commonest site of ectopic pregnancy are the fallopian tubes. Tubal pregnancy comprises about 95% of all ectopic pregnancies.
- Ampullary region of the fallopian tubes- The ovum implants most commonly in the ampullary region of the fallopian tubes- this is also the widest part of the tube and the region where fertilization normally occurs in a healthy pregnancy.
- Isthmic region of the fallopian tubes- The second commonest site of implantation is the isthmic part of the tubes - this is a part of the tube with very thin walls and is present between the ampullary region of the tubes and the uterus. Due to the thin walls, rupture of the ectopic pregnancy occurs very early; as early as 4 - 5 weeks of pregnancy.
- Fimbrial pregnancy– The fimbrial part of the tube is the part closest to the ovaries. It has a number of fingerlike projections called the fimbriae which is responsible for picking up the ovum after ovulation. If ectopic pregnancy occurs at this region, the tubes usually do not rupture. The embryo is aborted out of the fimbrial opening into the abdomen, leading to secondary abdominal pregnancy.
- Interstitial pregnancy– In this type of ectopic pregnancy, the pregnancy occurs inside the uterine opening of the tube that runs through the musculature of the uterus.
- Abdominal Pregnancy: Ectopic pregnancy can occur very rarely in the abdominal cavity. It is usually a result of the embryo being aborted intact from the tube. Occasionally, the tube can rupture with minimal bleeding, gently pushing the embryo into the abdominal cavity. The embryo develops in this ectopic site by attaching its placenta to the bowels, omentum, broad ligament or any other abdominal organ. But it is rare for the fetus to develop completely to term in this site. Death usually occurs at around 20- 28 weeks of pregnancy.
- Ovaries: Ectopic pregnancy can occur very rarely on the surface of the ovaries.
CAUSES OF ECTOPIC PREGNANCY
The fertilized ovum takes about 7 - 10 days to reach the uterus from its site of fertilization in the tubes (see How pregnancy occurs). If the movement of the fertilized ovum from the tubes to the uterus is slowed down due to any reason, the ovum will implant at the region that it reaches on the 7-10th day. So the causes for ectopic pregnancy are the same causes that decreases the movement of the ovum forwards to the uterus.
- Infections: Infections and inflammations inside the tube can destroy the ciliary cells of the tubes that propel the ovum forwards. This can decrease the speed of movement of the ovum causing it to remain inside the tubes even at the time it becomes capapble of implantation.
Causes of infections may be previous abortions, appendicitis, pelvic inflammatory diseases, intrauterine contraceptive devices like loops, or any surgery in the pelvis. Previous pelvic infection is the commonest cause of ectopic pregnancy.
- Pelvic tumours: Tumours like fibroids or ovarian tumours can cause kinking of the tube and slow down the ovum. This can lead to ectopic pregnancy
- Surgery of the tubes: With more and more tubal surgeries being carried out nowadays, it is fast becoming one of the commoner causes of ectopic pregnancy. Surgery on the tubes becomes necessary in the management of infertility to remove any block in the tubes, or in reversal operations of the tubes after tubal sterilizations.
- Anatomical defect of the tube: The tubes may be defective at birth. The tubes may be too long (Congenital tubal elongation) or too short (tubal hypoplasia). These are very rare causes of ectopic pregnancy.
SIGNS AND SYMPTOMS OF ECTOPIC PREGNANCY
The embryo can grow up to a maximum of 8 weeks in the tubes. At 8 weeks, and usually by 6th week, the tube ruptures as it cannot support the developing embryo any more.
The signs and symptoms of ectopic pregnancy depend on whether the patient is examined before or after the tubes have ruptured.
BEFORE RUPTURE OF THE TUBES
- Signs and symptoms of very early pregnancy: The patient usually has all the signs and symptoms of very early pregnancy:
- Missed periods: She will complain of missed periods of a few weeks duration- usually less than 6 weeks and definitely not more than 8 weeks of pregnancy.
- Nausea and vomiting which is usually mild.
- Sore breasts.
- Loss of appetite.
- Frequency of passing urine.
- Fatigue.
- Mild vaginal bleeding or brown stained discharge: She may come with complains of mild bleeding or even only brown stained discharge. She may confuse this bleeding with implantation bleeding or the start of an abortion.
- Pain:
She may have pain in her lower abdomen. The pain is usually spasmodic in nature with occasional cramps. Sometimes it may be so mild as to cause only a discomfort or mild pain while walking or standing up from a sitting down position. Sometimes however there may be an acute stabbing pain that causes the patient to double up.
DIAGNOSIS OF UNRUPTURED ECTOPIC PREGNANCY
Unruptured ectopic pregnancy is diagnosed by:
- Signs and symptoms: as described above.
- Positive pregnancy test: The pregnancy test in most patients with ectopic pregnancy is usually 'weakly positive', that is, the line that appears in the kit in reaction to the urine looks faded and not very clear. This is due to the fact that the placenta fails to develop properly in the tubes and the level of HCG in the blood is consequently very low.
- Ultrasonography: The empty uterus and the presence of the gestational product outside the uterus is easily identifiable.
AFTER RUPTURE OF THE TUBES
- Shock: The fallopian tube ruptures when it cannot sustain the growing embryo any more (usually at about 7 - 8 weeks of pregnancy, sometimes even sooner). The rupture of the tube causes severe bleeding into the abdominal cavity, although bleeding through vagina will be minimal.
Once severe bleeding due to rupture of the tube occurs, the patient goes into a state of shock. There is severe pallor, hands and feet feel cold and clammy, blood pressure is low or unrecordable , pulse is thin and thready as well as other signs and symptoms of shock. Death can occur very quickly, if treatment is not immediate.
- History of early pregnancy with mild bleeding per vagina is present.
- Pregnancy test is positive.
TREATMENT OF ECTOPIC PREGNANCY
Unruptured tubal pregnancy: It is possible to go for medical treatment of unruptured ectopic pregnancy, if it is diagnosed early enough.
- Medical treatment: Methotrexate is a lethal drug that can cause death to the embryo. It is prescribed as tablets to be taken strictly under medical supervision. The drug causes severe depletion of folic acid in the body, so tablets of folic acid have to be prescribed simultaneously. Other embryotoxic drugs like Mifeprostone can also be given.
The dead embryo gradually degenerates and is reabsorbed into the body.
- Surgery - Many doctors prefer surgical treatment as the first line of treatment. Usually, laparoscopic surgery (also called 'pinhole surgery'), is carried out and the embryo with all other products of gestation like placenta are removed. The advantage of this method is that the patient is immediately cured whereas in treatment with medicines, it takes 2-3 days under careful supervision, but the disadvantage is that as it is a surgical method, it carries all the risks of surgery- patient has to be hospitalised, risks of anaesthesia, it is expensive etc.
Methotrexate can also be directly injected into the embryo during laparoscopy. The embryo need not be taken out as it will die and degenerate. This cuts down considerably on the time taken for operation.
Ruptured tubal pregnancy:
- Immediate Treatment: The immediate treatment is to support the patient and combat the shock. IV fluids, blood transfusion etc are started as early as possible.
Immediate surgery should be done to stem the blood flow, rather than to remove the embryo. As soon as the operation is started and the abdomen is opened, the ruptured edges of the tube is identified, and the bleeding blood vessels tied. This stops the bleeding immediately. It is only then that the embryo is searched for and taken out.
- Supportive treatment: The patient is supported with IV fluids, blood transfusion, medicines etc.
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