Heterotopic pregnancy: a womb pregnancy with an ectopic pregnancy

ISUOG, the international society for ultrasound in obstetrics and gynaecology, explains that normally an egg is fertilised in the tube and the embryo moves to the womb. If the embryo cannot reach the womb it implants outside it, causing an ectopic pregnancy. A heterotopic pregnancy is regarded as a multiple pregnancy, with one embryo in the womb and one outside. The NHS says an ectopic pregnancy usually happens in a fallopian tube and that it is not possible to save an ectopic pregnancy; heterotopic pregnancy is different because a healthy pregnancy in the womb may be present too.

ISUOG says the ectopic part is most often in the fallopian tube but can be in the cervix, ovary, a previous caesarean scar or even the abdomen.

ISUOG puts the frequency at about 1 in 30,000 spontaneous pregnancies, stating the risk is 30 to 60 times higher if pregnancy was achieved by assisted reproduction. It lists tubal causes such as infection, tubal surgery, a previous ectopic pregnancy or sterilisation as major risk factors, as with a straightforward ectopic pregnancy. The actual cause is unknown, and ISUOG describes two hypotheses: two eggs fertilised at the same time that implant in different places, or a further egg that implants in the womb after an ectopic pregnancy has already formed.

For ectopic pregnancy in general, the NHS lists pelvic inflammatory disease, previous ectopic pregnancy, tubal surgery, fertility treatment, becoming pregnant with an IUD or IUS in place, smoking and age over 35 as associated with greater risk. It says around 1 in 90 pregnancies in the UK is ectopic.

ISUOG says symptoms are variable and non-specific, and that about half of patients have none. They can include a missed period, lower abdominal pain on one or both sides, shoulder-tip pain from blood leaking into the abdomen (a sign the condition is worsening), and vaginal bleeding that is lighter or darker than a period. If an ectopic pregnancy ruptures, ISUOG describes severe sharp pain and possible shock with clammy skin, rapid breathing, rapid pulse, low blood pressure and unconsciousness, which are medical emergencies.

The NHS says to call 999 or go to A&E if you have a combination of sudden, sharp, intense tummy pain, feeling very dizzy or fainting, feeling sick and looking very pale, which could mean a tube has split. It says deaths from rupture are extremely rare in the UK. Contact your GP or call NHS 111 for a combination of symptoms such as tummy pain low down on one side, bleeding, shoulder-tip pain and discomfort when peeing or pooing if you might be pregnant.

ISUOG explains that symptoms can be mistaken for other early pregnancy complications because there is also a pregnancy in the womb. The hCG blood level may not help establish the diagnosis because of the pregnancy in the womb. Diagnosis relies on examination and, above all, a transvaginal ultrasound showing a gestation sac in the womb together with an ectopic pregnancy containing an embryo or yolk sac. Sometimes the ectopic pregnancy shows neither, which makes diagnosis harder. A haemorrhagic corpus luteum cyst can look and feel like a heterotopic pregnancy.

ISUOG lists three ways to treat the ectopic part: expectant management (watch and wait), medical treatment with an injection into the ectopic pregnancy to make it regress, or surgery by laparoscopy or open surgery. If you arrive in a life-threatening condition from a ruptured ectopic pregnancy, urgent surgery is needed. If you are stable, your doctor discusses the options based on the location and size of the ectopic pregnancy and your wish to have a baby, explaining the risks and advising immediate return if signs of rupture appear.

For an ordinary ectopic pregnancy the NHS describes expectant management, a methotrexate injection or keyhole surgery as the three main treatments. In a heterotopic pregnancy the choice is made by a specialist team that also has the pregnancy in the womb to consider. ISUOG suggests asking about your chances of preserving the pregnancy in the womb and about follow-up arrangements.

ISUOG says the chance of a heterotopic pregnancy happening again is extremely low. It also suggests asking how long to wait before trying again and what special precautions to take in a future pregnancy. The NHS says to let your GP know early if you become pregnant after an ectopic pregnancy so early scans can check everything is OK, and that many women feel grief after losing a pregnancy, with feelings that can last several months; support groups include the Ectopic Pregnancy Trust and Miscarriage UK. Care pathways for early pregnancy complications differ across the UK nations.