Preterm labour:
is defined as the presence of uterine
contractions of sufficient frequency and
intensity to effect progressive effacement and
dilation of the cervix prior to term gestation
(between 20 and 37 weeks of gestation).
Preterm labour precedes almost half of
preterm births .
preterm birth occurs in 12% of pregnancies
and is the leading cause of neonatal mortality in
the United States.
.
Preterm birth accounts for 70% of
neonatal morbidity, mortality.
Risk of death or neuro-sensory
disability increases with decreasing
gestational age.
In the UK, infant mortality among
Preterm births was 42/1000 live
births in 2005, compared with
5/1000 live births overall.
Aetiology and Risk factors:
It can affect any pregnancy and many women
have no known risk factors.
Many factors can increase the risk of preterm
labour, including:
•
Previous preterm labour .
•
or premature rupture of membrane , particularly
in the most recent pregnancy or in more than
one previous pregnancy.
•
Overdistened Uterus associated with multiple
pregnancy as twin, triplets or polyhydramnios.
•
problems with the uterus, cervix or placenta
such as uterine anomalies, cervical
incompetence, placental abruption.
•
Smoking, alcohol or illicit drugs.
•
Certain infections, genital tract like bacterial
vaginosis caused by Gardenella vaginalis.
•
Being underweight or overweight before
pregnancy, or gaining too little or too much
weight during pregnancy.
•
Stressful life events, such as the death of a
loved one.
•
Domestic violence or any form of abuse
during pregnancy.
•
Multiple miscarriages
Some chronic conditions, like hypertension
and diabetes.
•
Pregnancy complications, such as
preeclampsia,vaginal bleeding.
•
Presence of a foetal birth defect or foetal
death.
•
Little or no prenatal care.
•
An interval of less than six months since the
last pregnancy.
Specific risks for the preterm neonate:
Preterm infants usually show physical signs of
prematurity in reverse proportion to the gestational
age. As a result there are medical problems affecting
different organ systems.
•Respiratory problems are common; specifically the
(RDS or IRDS).
•Another problem can be
(previously called bronchopulmonary dysplasia).
•
, it affects 25
percent of babies born preterm, usually before
32 weeks of pregnancy.Mild brain bleeding
usually leave no or few complications, but severe
bleeding often result in brain damage or even
death.
•Neurodevelopmental problems have been
linked to lack of maternal
, at a
time when their own
postnatal needs.
Children born preterm are more likely to have
white matter brain abnormalities early on causing
higher risks of cognitive dysfunction.
White matter connectivity between the frontal and
posterior brain region is critical in learning to
identify patterns in language.
. Preterm children are at a greater risk for having
poor connectivity between these areas leading to
learning disabilities.
Neurological problems include
,
hypoxic-ischemic
,
•Cardiovascular complications may arise from the failure
of the ductus arteriosus to close after birth:
.
-Gastrointestinal and metabolic problems can arise from
, feeding difficulties,
of
prematurity,
,
, and
necrotizing enterocolitis
•Hematologic complications include
,
, and hyperbilirubinemia
that can lead to
.
Infection, including
,
, and UTI.
Management of Preterm Labour:
Goals of obstetric patient management of preterm
labour should include:
(1) Early identification of risk factors associated with
preterm birth.
(2) Timely diagnosis of preterm labour.
(3) Identifying the aetiology of preterm labour.
(4) Evaluating foetal well-being.
(5) Providing prophylactic pharmacologic therapy to
prolong gestation and reduce the incidence of
respiratory distress syndrome (RDS) and intra-
amniotic infection (IAI).
(6) Initiating tocolytic therapy when indicated.
(7) Establishing a plan of maternal and foetal
surveillance to improve neonatal outcome .
Diagnosis:
Symptoms; includes:
•
Regular contractions
— Contractions of sufficient frequency
and intensity to effect progressive effacement and dilation of the
cervix at 24-37 weeks’ gestation .
•
a tightening sensation in the abdomen.
.Constant low, dull backache.
•
Mild abdominal cramps.
•
Vaginal spotting or bleeding.
•
Watery vaginal discharge in a gush or a trickle.
•
A change in vaginal discharge.
.Risk factors.
PHYSICAL EXAM:
Vital signs: PR, RR, Temp., Bp.
Chest and CVS exam,
Abdominal exam.
For uterus size, uterine contractions, the lie and
presenting part with foetal heart rate.
Pelvic exam .; for signs of labour.
and for presence or absence of signs of genital tract
infection
.
INVESTIGATIONS Specific for PTL:
Fetal fibronectin:
It is glycoprotein secreted by chorionic cells.
It’s presence in the cervical or vaginal secretions
indicates that the border between the chorion and
deciduas has been disrupted.
A positive test between 20- 36 weeks indicates an
increased risk of preterm birth.
It is normally positive before 20 weeks of
gestation and after 36 weeks of gestation
Negative between 20 -36 weeks of gestation.
If the diagnosis of preterm labour is suspected, but not
confirmed, it may be first obtain a vaginal foetal
fibronectin sample before pelvic cervical examination.
If the diagnosis remains in doubt after the exam, the
specimen can be sent to the lab for analysis.
Ultrasonography of the cervix & obestetric U/S:
At 24 weeks gestation a cervix length of less than 25 mm
defines a risk group for preterm birth, the shorter the
cervix the greater the risk.
In women with preterm contractions, cervical length
exceeds 30 mm are unlikely to deliver within the next
week.
Evaluate for the presence of genital tract
infection:
Tocolytics are contraindicated in the presence of
symptomatic intra amniotic infection.
The definition of intra amniotic infection (ie,
chorioamnionitis) includes a temperature greater than
38.0°C (100.0°F) and 2 of the 5 following signs:
•WBC count greater than 15,000 cells/mm
3
•Maternal tachycardia greater than 100 beats per
minute .
•Foetal tachycardia greater than 160 bpm.
•Tender uterus
•Foul-smelling discharge
TREATMENT:
Admission to hospital with intensive neonatal care.
We have to decide to actively manage the labour or
stop it.
A- INDICATIONS to continue the labour:
Advanced labour cervical dilatation more than 3 cm
and fully effaced cervix.
Premature rupture of membranes and uterine
contractions.
There is ante partum haemorrhage.
There is chorio- amnionitis .
Foetal compromise.
Congenital malformation and foetal death.
Severe pre- eclampsia
.
Management during Labour:
First Stage:
Second Stage:
Third Stage:
Indications of Operative delivery;
B- To stop uterine contractions using:
Tocolytic Drugs:
Medications that been used to stop uterine
contractions.
It’s also use In the management of intra
partum foetal distress and impaired foetal
growth and to facilitate external cephalic
version at term.
- Aimed at preventing the onset of preterm labour, for
women at risk of preterm birth.
- Interventions to improve outcome for foetuses at risk
of being born preterm
,
as those needing transfer to a
hospital which can provide neonatal intensive care.
- Use for time to let action of antenatal corticosteroids
in
those who have not yet completed a full course of
corticosteroids
and magnesium sulphate for
neuroprotection.
It’s Action: The concentration of calcium in the
myometrial cell dictates the degree of contractility.
- Levels of intracellular calcium and calcium
flux are regulated by a variety of mechanisms, it
rises either because calcium enters the cell from
outside through voltage gated calcium channels, or
because it is released from the sarcoplasmic reticulum.
Tocolytics exert their effect by reducing the level of
intracellular calcium.
Use them associated with a prolongation of pregnancy
for up to 7 days but with no significant effect on
preterm birth and no clear effect on prenatal or
neonatal morbidity.
Tocolysis should not be used where there is a
contraindication to prolonging pregnancy.
Using multiple tocolytic drugs associated with a higher
risk of adverse effects and so should be avoided.
When using a tocolytic drug, the best choice is the most
effective with the fewest adverse effects, both
immediate and long-term.
CALCIUM CHANNEL BLOCKERS:
There are two types of calcium channels in the
myometrial cell, the L type and the T-type.
Nifedipine binds to the inside of myometrial L-type
voltage dependent calcium channels causing them to
remain closed, and so inhibits contractility.
However, these L type channels are present in other
types of smooth muscle cells such as vascular smooth
muscle.
The T type calcium channel is peculiar to
myometrium.
Calcium channel blockers were associated with:
Less neonatal respiratory distress syndrome;
Less necrotising entero colitis ;
and less intraventricular haemorrhage than other
tocolytic drugs.
Nifedipine, the most commonly used , crosses the
placenta,but whether
it has any long-term effect on
the foetus is uncertain.
Animal studies with very high doses have reported
abnormalities of foetal and placental blood flow and
abnormal digital development. No congenital defects
have been associated with its use in humans.
.The dose of nifedipine is an initial oral dose of 20 mg followed
by 10–20 mg three to four times
daily, adjusted according to
uterine activity for up to 48 hours. A total dose above 60 mg
associated with a three- to four-fold increase in adverse events
such as headache and hypotension.
Nifedipine and atosiban have comparable effectiveness in
delaying birth for up to seven days.
Compared with beta-agonists, nifedipine is associated with
improvement in neonatal outcome.
Ritodrine and atosiban are licensed in the UK for the
treatment of threatened preterm labour ,while nifedipine
is an unlicensed for PTL, it has the advantages of oral
administration and a low purchase.
Cyclo-oxygenase (COX) inhibitors:
Cyclo-oxygenase enzymes contribute to production of
prostaglandins, which are important in the onset and
maintenance of labour so inhibitors of the inducible
COX-2 enzyme might be effective tocolytics .
Indomethacin is the commonly used for tocolysis.
COX inhibitors cross the placenta and potential adverse
effects for the foetus include premature closure of the
ductus arteriosus with consequent pulmonary
hypertension, persistent patent ductus arteriosus,
necrotising entero-colitis and intra-ventricular
haemorrhage.
Magnesium sulphate:
There is no clear evidence that magnesium sulphate
reduces the risk of preterm birth but it’s administration
to women at risk of preterm labour reduces the risk of
cerebral palsy. It should be received for 24 hours to
reduce this.
Beta-agonists: (ritoridine ,salbutamol)
They have a high frequency of adverse effects.
Nifedipine, atosiban and the COX inhibitors have fewer
types of adverse effects, and they occur less frequently
than for beta-agonists.
.All beta-agonists, have unpleasant or
potentially life threatening adverse effects for the
woman better use a safer alternative.
Adverse effects, include palpitations, tremor,
nausea or vomiting, headache, chest pain and
dyspnoea
.
Rare but serious complication of beta agonists
there are case reports of a small number of
maternal deaths associated with use them.
Pulmonary oedema is another complication
.
PROGESTERONE:
It is present in high concentrations during
pregnancy, increases cAMP production. cAMP and
cGMP maintain uterine quiescence by promoting
the uptake of intracellular calcium into the
sarcoplasmic reticulum and thereby reducing
intracellular calcium concentrations and reducing
contractility. They also lower the amount of
phosphorylated myosin and promote myometrial
relaxation.
Atosiban:
It is anti- oxytocin ,
suggested dose of atosiban of
an initial bolus dose of 6.75 mg over 1 minute,
followed by an infusion of
18 mg/hour for 3
hours, then 6 mg/hour for up to 45 hours (to a
maximum of 330 mg).
In multiple pregnancy whether or not tocolysis
leads to any benefit in preterm labour,
although
both nifedipine and atosiban have been widely
used .
Prevention:
We might not be able to prevent preterm labour , but
there's much we can do to promote such as:
•
Regular prenatal care; can help in monitoring maternal
and foetal wellbeing.
•
Diet: more folic acid, calcium, iron.
•
Gain weight: Gaining the right amount of weight can
support foetal health.
•
A weight gain of 25 to 35 pounds (about 11 to 16
kilograms) is recommended.
•
Avoid risky substances; quit smoking. It might trigger
preterm labour. Alcohol and illicit drugs are off-limits
Pregnancy spacing:
Some researches suggest a link between
pregnancies spaced less than six months apart and
an increased risk of premature birth.
.When using assisted reproductive technology:
Multiple pregnancies carry a higher risk of preterm
labour.
Taking medications:
Treatment with a vaginal progesterone gel during
the second and third trimesters might decrease the
risk of preterm birth in women who have short
cervixes.
•
Sexual activity:
If the patient had a history of
preterm labour or experience signs or symptoms of
preterm labour, she might need to restrict sexual
activity
•
Regarding physical activities:
Avoiding heavy lifting.
Managing chronic conditions:
Certain conditions, such as diabetes and high
blood pressure, increase the risk of preterm labour;
control them before conception.