17 yo female with progestin secreting IUD, LMP 9/22/17, no prior medical problems presents to the ED with bilateral lower abdominal pain for the last day. She also notes that she has had some intermittent vaginal bleeding for the last 3 weeks. Her HR is 98, BP 130/99, RR16, sat 100% on RA. On exam she is well appearing but with bilateral lower abdominal tenderness. A urine pregnancy test is positive. A quick bedside US reveals free fluid in her pelvis without an IUP. You consult GYN for suspected ruptured ectopic.

You try to remember how progesterone works during the menstrual cycle and therefore how progestin IUD’s might work? You wonder how that might also increase the risk of ectopic pregnancy.

 

A: Immediately following ovulation, the mature follicle degenerates into the corpus luteum that begins secreting progesterone that:

  1. Prepares the endometrium for implantation.
  2. Thickens the mucus at the cervical os to prevent additional sperm from passing into the uterus.
  3. Through a negative feedback loop, stops the secretion of LH and FSH from the anterior pituitary, and therefore halts the process of follicle development and ovulation.
  4. Progesterone may also have an impact on tubal motility, which increases the risk for pregnancies to become ectopic.  

What is the risk for having an ectopic pregnancy with an IUD?

 

The European Active Surveillance Study for Intrauterine Devices by Heinemann et. al. followed a cohort of 58,323 women with levonorgesterel-releasing IUD (41,000, mean age 37) or copper IUD (17,323, mean age 34) from 6 European countries. Their loss to follow up was only 2%.

 

At 1 year, they found 26 women with levonorgestrel IUDs (0.06%) and 92 women with copper IUDs (0.5%) had unplanned pregnancies. Of those unplanned pregnancies, 7 women with levo-IUDs (27%) and 14 women with copper IUDs (15%)  had an ectopic pregnancy.

 

TLDR: IUDs, while very effective at reducing the risk for unplanned pregnancy, are a significant risk factor for ectopic pregnancy; 1 in 4 women with a levonorgestrel IUD and an unplanned pregnancy were ectopic in this study.

 

Source:

Heinemann K. et. al. Comparative contraceptive effectiveness of levonorgestrel-releasing and copper intrauterine devices: the European Active Surveillance Study for Intrauterine Devices.Contraception. 2015 Apr;91(4):280-3. doi: 10.1016/j.contraception.2015.01.011. Epub 2015 Jan 16.

Hormonal Contraception. https://courses.washington.edu/conj/bess/contraception/contraception.htm