A heterotopic pregnancy is a multiple gestation in which there is an ectopic pregnancy present at the same time as a potentially viable intrauterine pregnancy. In other words, one fetus has implanted outside the uterus (usually in the fallopian tubes) while the other(s) is in the uterus. A heterotopic pregnancy can be every bit as dangerous as an ectopic pregnancy, but there are extra considerations in planning treatment, given that parents usually prefer not to terminate the entire pregnancy.
Like all multiple pregnancies, heterotopic pregnancy is most common in couples who conceive with assisted reproduction. As many as 1-2 in 1,000 of all pregnancies following fertility treatments may involve a heterotopic pregnancy. But heterotopic pregnancy is fairly rare in women who conceive without fertility treatment, with some estimates suggesting heterotopic pregnancy rates of about 1 in 10,000 to 1 in 30,000 spontaneous (natural) conceptions.
Symptoms of Heterotopic Pregnancy:
A heterotopic pregnancy may or may not have symptoms. About 50% are diagnosed only when the fallopian tube ruptures, at which point emergency surgery is needed. If symptoms are present prior to a ruptured tube, the symptoms are the same as those of ectopic pregnancy (usually pain/cramping and spotting).
Diagnosis of Heterotopic Pregnancy:
It's very difficult for doctors to diagnose heterotopic pregnancy early. Women may have bleeding and cramping, but these symptoms can occur even in a normal pregnancy -- and since ultrasound will show a baby implanted in the uterus, it's very easy for a heterotopic pregnancy to be missed.
Thus, doctors are still struggling with the question of how to diagnose these pregnancies early. Several experts have recommended that all high-risk women who continue to have ectopic pregnancy symptoms despite a confirmed pregnancy in the uterus should be screened for heterotopic pregnancy.
Treatment of Heterotopic Pregnancy:
Heterotopic pregnancies usually need treatment upon detection and carry the same risks that any other ectopic pregnancy would carry. It is usually possible to treat heterotopic pregnancies without terminating the intrauterine pregnancy, but this typically means surgical treatment, which may or may not involve removal of the affected fallopian tube.
Some studies have found that heterotopic pregnancies also carry an increased risk of miscarriage of the intrauterine pregnancy (especially if the heterotopic pregnancy was diagnosed after rupture), but about two-thirds of women are able to carry the intrauterine baby to term following treatment, so chances are good that the remainder of the pregnancy will be fine.
If you have had treatment for a heterotopic pregnancy and have continued with your intrauterine pregnancy, it's normal if you find yourself feeling a sense of loss over the baby that was implanted outside the womb, and it's okay to grieve that baby even though you're looking forward to the rest of your pregnancy.
Beyer, Derek A. and Daniel A. Dumesic. Heterotopic pregnancy: an emerging diagnostic challenge." The Journal of Family Practice. October 2002 (Vol. 14, No. 10).
Ludwig, M, M. Kaisib, O. Bauera and K. Diedrich. Heterotopic pregnancy in a spontaneous cycle: do not forget about it!" Eur J Obstet Gynecol Reprod Biol. 1999 Nov;87(1):91-3.
Tenore, Josie L. "Ectopic Pregnancy." Am Fam Physician 2000;61:1080-8.