A contraction stress test (CST) is performed near the end of

pregnancy Pregnancy is the time during which one or more offspring gestation, gestates inside a woman's uterus. A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Conception (biology), Conception usually occurs ...

(34 weeks' gestation) to determine how well the

fetus A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic development, embryonic stage, the fetal stage of development takes place. Pren ...

will cope with the contractions of

childbirth Childbirth, also known as labour, parturition and delivery, is the completion of pregnancy, where one or more Fetus, fetuses exits the Womb, internal environment of the mother via vaginal delivery or caesarean section and becomes a newborn to ...

. The aim is to induce contractions and monitor the

to check for

heart rate Heart rate is the frequency of the cardiac cycle, heartbeat measured by the number of contractions of the heart per minute (''beats per minute'', or bpm). The heart rate varies according to the body's Human body, physical needs, including the nee ...

abnormalities using a

cardiotocograph Cardiotocography (CTG) is a technique used to monitor the fetal heartbeat and uterine contractions during pregnancy and labour. The machine used to perform the monitoring is called a cardiotocograph. Fetal heart sounds were described as early a ...

. A CST is one type of antenatal fetal surveillance technique. During uterine contractions, fetal oxygenation is worsened. Late decelerations in

fetal heart rate A fetus or foetus (; : fetuses, foetuses, rarely feti or foeti) is the unborn offspring of a viviparous animal that develops from an embryo. Following the embryonic stage, the fetal stage of development takes place. Prenatal development is a ...

occurring during uterine contractions are associated with increased fetal death rate,

growth retardation A delayed milestone, which is also known as a developmental delay, refers to a situation where a child does not reach a particular developmental milestone at the expected age. Developmental milestones refer to a collection of indicators that a chil ...

and neonatal depression. This test assesses fetal heart rate in response to uterine contractions via

electronic fetal monitoring Cardiotocography (CTG) is a technique used to monitor the fetal heartbeat and uterine contractions during pregnancy and labour. The machine used to perform the monitoring is called a cardiotocograph. Fetal heart sounds were described as early ...

. Uterine activity is monitored by tocodynamometer.

Medical uses

The CST is used for its high

negative predictive value The positive and negative predictive values (PPV and NPV respectively) are the proportions of positive and negative results in statistics and diagnostic tests that are true positive and true negative results, respectively. The PPV and NPV desc ...

. A negative result is highly predictive of fetal wellbeing and tolerance of labor. The test has a poor

positive predictive value The positive and negative predictive values (PPV and NPV respectively) are the proportions of positive and negative results in statistics and diagnostic tests that are true positive and true negative results, respectively. The PPV and NPV desc ...

with false-positive results in as many as 30% of cases. A positive CST indicates high risk of fetal death due to hypoxia and is a contraindication to

labor Labour or labor may refer to: * Childbirth, the delivery of a baby * Labour (human activity), or work ** Manual labour, physical work ** Wage labour, a socioeconomic relationship between a worker and an employer ** Organized labour and the labour ...

. Patient's obstetricians usually consider operative delivery in such situations.

Contraindications

This "stress test" is usually not performed if there are any signs of

premature birth Preterm birth, also known as premature birth, is the birth of a baby at fewer than 37 weeks gestational age, as opposed to full-term delivery at approximately 40 weeks. Extreme preterm is less than 28 weeks, very early preterm birth is betwee ...

placenta praevia Placenta praevia or placenta previa is when the placenta attaches inside the uterus but in a position near or over the cervical opening. Symptoms include vaginal bleeding in the second half of pregnancy. The bleeding is bright red and tends not ...

vasa praevia Vasa praevia or vasa previa is a complication of obstetrics in which fetal blood vessels cross or run near the internal opening of the uterus. Since these vessels are not protected by the umbilical cord or placental tissue, the rupture of the fe ...

cervical incompetence Cervical weakness, also called cervical incompetence or cervical insufficiency, is a medical condition of pregnancy in which the cervix begins to dilate (widen) and efface (thin) before the pregnancy has reached term. Definitions of cervical weakn ...

multiple gestation A multiple birth is the culmination of a multiple pregnancy, wherein the mother gives birth to two or more babies. A term most applicable to vertebrate species, multiple births occur in most kinds of mammals, with varying frequencies. Such births ...

, previous classic

caesarian section Caesarean section, also known as C-section, cesarean, or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen. It is often performed because vaginal delivery would ...

. Other contraindications include but are not limited to previous uterine incision with scarring, previous

myomectomy Myomectomy, sometimes also called fibroidectomy, refers to the surgical removal of uterine leiomyomas, also known as fibroids. In contrast to a hysterectomy, the uterus remains preserved and the woman retains her reproductive potential. It still ...

entering the uterine cavity, and

PROM A promenade dance or prom is a formal dance party for graduating high school students at the end of the school year. Students participating in the prom will typically vote for a ''prom king'' and ''prom queen''. Other students may be honored ...

. Any contraindication to labor is contraindication to CST.

Procedure

CST is performed weekly, as the fetus is assumed to be healthy after a negative test and should remain so for another week. This test is done in hospital or clinic setting. External fetal monitors are put in place and then either

nipple stimulation Nipple stimulation or breast stimulation is stimulation of the breast. Stimulation may be by breastfeeding, sexual activity, an indirect non-sexual response, or kissing the nipple. As part of sexual activity, the practice may be performed upon, ...

or IV pitocin (oxytocin) is used to stimulate uterine contractions.

Nipple stimulation

This is a procedure that relies on

endogenous Endogeny, in biology, refers to the property of originating or developing from within an organism, tissue, or cell. For example, ''endogenous substances'', and ''endogenous processes'' are those that originate within a living system (e.g. an ...

release of

oxytocin Oxytocin is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. Present in animals since early stages of evolution, in humans it plays roles in behavior that include Human bonding, ...

following

nipple The nipple is a raised region of tissue on the surface of the breast from which, in lactating females, breast milk, milk from the mammary gland leaves the body through the lactiferous ducts to Breastfeeding, nurse an infant. The milk can flow th ...

stimulation, and is conducted by the patient. The

nurse Nursing is a health care profession that "integrates the art and science of caring and focuses on the protection, promotion, and optimization of health and human functioning; prevention of illness and injury; facilitation of healing; and alle ...

instructs the patient on the procedure, as follows. One nipple is massaged gently through clothing until a contraction begins, or for a maximum of 2 minutes. If at least 3 contractions in 10 minutes is not achieved, then the patient rests for 5 minutes and the other nipple is stimulated.American College of Obstetricians and Gynecologists (ACOG). (1999). Antepartum fetal surveillance (Practice Bulletin No. 9). Washington, DC: Author.

Oxytocin challenge test (OCT)

If adequate contractions (at least 3 in 10 minutes) cannot be achieved with nipple stimulation, an oxytocin challenge test may be performed. It involves the

intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutr ...

administration of

exogenous In a variety of contexts, exogeny or exogeneity () is the fact of an action or object originating externally. It is the opposite of endogeneity or endogeny, the fact of being influenced from within a system. Economics In an economic model, an ...

to the pregnant woman. The target is to achieve around three contractions every ten minutes.

Interpretation

History

The CST was the first antenatal surveillance test that was developed after the development of the

. The oxytocin challenge test was first described in 1972 and was standardised in 1975 when the parameters of contraction number and frequency were given. Historically, a CST was done after a non reactive NST. Today, a biophysical profile (BPP) is usually performed.

References

External links

Contraction Stress Test
at webmd.com {{Pregnancy Tests during pregnancy