1/30/05njmb

**Q**. Which fetal heart rate and contraction patterns are worrisome
with misoprostol use?

**A.** The hyperstimulation syndrome is worrisome and contraindicates
further use of the drug.

See Below

**Misoprostol and its possible adverse effects**

There are 3 types of uterine contraction patterns associated with
misoprostol use, only one of which is worrisome:

1\) tachysystole refers to the occurrence of more than 7 uterine
contractions in any 15 minute monitoring window,

2\) hypertonus refers to 2 or more uterine contractions lasting more
than 120 seconds in any 15 minute monitoring window,  

3\) the hyperstimulation syndrome refers to any instance of 1) or 2)
accompanied by a nonreassuring fetal heart tracing (i.e., tachycardia,
decreased variability, repetitive variables or lates).

Only the hyperstimulation syndrome is worrisome and contraindicates use
of the drug for further attempts at ripening or induction. It\'s
incidence in most studies is usually under 5%. Tachysystole in early
labor after use of misoprostol is a common finding and is usually not a
cause of either maternal discomfort or fetal intolerance of the process,
and does not contraindicate further usage.

**George Gilson, MD, Tuesday, January 18, 2005 5:05 PM**

**UpToDate**

**Uterine contraction abnormalities** --- Abnormal or excessive uterine
contractions can occur with the use of prostaglandin compounds or
[oxytocin](http://www.uptodateonline.com/application/topic.asp?file=drug_l_z/190133&drug=true).
There are no uniform definitions for such terms as hyperstimulation,
tachysystole and hypertonus. The American College of Obstetricians and
Gynecologists offerred the following:

  ![](media/image1.png){width="6.25e-2in"
height="7.152777777777777e-2in"} Hyperstimulation can be defined as a
persistent pattern of more than five contractions in 10 minutes, uterine
contractions lasting at least two minutes, or contractions of normal
duration occurring within one minute of each other, with or without
fetal heart rate changes.\
\
  ![](media/image1.png){width="6.25e-2in"
height="7.152777777777777e-2in"} Tachysystole can be defined as
hyperstimulation without fetal heart rate changes.\
\
  ![](media/image1.png){width="6.25e-2in"
height="7.152777777777777e-2in"} Hyperstimulation syndrome has been used
to describe hyperstimulation or tachysystole associated with fetal heart
rate abnormalities.

Other authorities use alternative terminology.

-the term \"uterine hyperstimulation without fetal heart rate changes\"
is used to describe uterine tachysystole (\>5 contractions per 10
minutes for at least 20 minutes) and

-uterine hypersystole/hypertonus (a contraction lasting at least two
minutes) and

-the term \"uterine hyperstimulation with FHR changes\" is used to
denote uterine hyperstimulation syndrome (tachysystole or hypersystole
with fetal heart rate changes such as persistent decelerations,
tachycardia or decreased short term variability.

The reader is encouraged to be mindful of these semantic differences.

Rarely, hyperstimulation or tachysystole may cause uterine rupture.

The various PGE2 preparations have up to a 5 percent rate of uterine
hyperstimulation, which is usually well tolerated and not associated
with an adverse outcome. The reported risk of hyperstimulation with
[oxytocin](http://www.uptodateonline.com/application/topic.asp?file=drug_l_z/190133&drug=true)
varies widely. Both tachysystole and hyperstimulation occur more
frequently when higher doses of oxytocin, prostaglandin E2, or
[misoprostol](http://www.uptodateonline.com/application/topic.asp?file=drug_l_z/169662&drug=true)
are used.

**Induction of labor: Indications, techniques, and complications**

<http://www.uptodateonline.com/application/topic.asp?file=labordel/8409&type=A&selectedTitle=4~32>