Heterotopic pregnancy is a rare situation when there is an intra-uterine and extra-uterine (i.e. ectopic) pregnancy occurring simultaneously.

Epidemiology

The estimated incidence in the general population is estimated at 1:30,000 (for a naturally conceived pregnancy ⁷). The incidence among patients with assisted reproduction is higher and is thought to be around 1-3:100 ². Due to this, the overall incidence has increased over the years.

Heterotopic pregnancies have been diagnosed from 5-34 weeks of gestation with up to 70% diagnosed between 5-8 weeks of gestation, 20% between 9-10 weeks, and only 10% after the 11^th week ⁶.

Pathology

Risk factors

Recognized risk factors predisposing to this condition include:

• assisted reproductive techniques: multiple embryo transfer and ovulation induction ⁸
• use of an intrauterine contraceptive device
• prior tubal surgery
• history of pelvic inflammatory disease
• history of a previous ectopic pregnancy 

Radiographic features

Ultrasound

Classically shows features of an intra-uterine pregnancy as well as an ectopic pregnancy.

Treatment and prognosis

An ultrasound-guided ablation or laparoscopic removal of the extra-uterine fetus can be considered in patients who have a known heterotopic pregnancy to permit the intrauterine pregnancy to continue normally.

Medical management, although used successfully for an ectopic pregnancy, has a limited role in the management of heterotopic pregnancy as one must try to preserve and protect the intrauterine pregnancy.

Differential diagnosis

Considerations include:

• ectopic pregnancy with an intra-uterine pseudogestational sac
• intra-uterine gestation with a hemorrhagic corpus luteum