Embryo transfer technique as a cause of ectopic pregnancies in in vitro fertilization.

Against an overall risk of around 2% ectopic pregnancies in in vitro fertilization programs around the world, we report an incidence more than three times greater (5 tubal ectopic pregnancies in 80 clinical in vitro fertilization pregnancies). Of two techniques used for embryo transfers, one produced a significantly higher risk for ectopic pregnancy (P less than 0.05). Four of the ectopic pregnancies occurred in a small group of 24 patients in whom the embryo transfer technique attempted to deliver the embryos at the uterine fundus (mean distance of catheter insertion 62.9 +/- 7.9 mm from the external cervical os). Only one ectopic pregnancy occurred in 56 patients whose embryos were transferred to a standard, generally midcavity position. It is concluded that the delivery catheter need be inserted only 55 mm as a routine and less in patients with a shortened cervix or with the hypoplastic uterus usually encountered in women with primary ovarian failure who have ovum or embryo donation. In such cases an ultrasonic measurement of length may indicate that a shorter transfer distance is required.