DELAYING AND INDUCING THE LABOUR AND ABORTION
THE UTERUS OR WOMB
The arrow marked A is the Uterus or Womb which serves as the carrier bag to protect the fetus for the entire duration of pregnancy normally of 266 to 300 days.Inside the uterus the endometrium the inner linings of the uterus become a cushion bed which has been nicely developed for luxurious stay of the fetus indicated by an arrow marked E in the above picture.This endometrium is developed and protected by an hormone from the corpus luteum of the ovary known as Progesterone the hormone of Pregnancy as it along with corpus luteum would be ceased either at the end of the pregnancy period or at the end of the menstural cycle if no fertilization resulted
The Uterine muscles are composed of pace makers similar to heart muscles wih a power of auto electrical contractive stimulus.The pace makers would automatically trigger the stimuli normally at the beginning and slowly increasein intensity and become strong at the completion of the normal pregnancy period of 266 to 300 days.The stimuli produce waves of contraction.The waves would easily be conducted through out the uterine muscles by the low contraction resisting cell gaps with rhythm.These cell junctions would be increased in number and maintained by the progesterone and estrogens as the pregnancy period grows into later trimesters.
Oxitocin a hormone from the posterior pituitary will be released throughout the pregnancy period.The hormone is a powerful contractor of uterine muscle will act on it to give a final strong stimuli to induce the labour for delivering the baby.
Eventhough the secretion of oxitocin is constant from the pituitary all the times and throughout the pregnancy period but the responsiveness of the uterine muscle to oxitocin is gradual.Slow at the beginning of the pregnancy period and peak at the last trimester.
Any pathalogical condition which disturb this system would result in abortion.
Abortions can be manually induced or prevented by treatments at various situations.
Drugs That Induce Abortions
1.Oxitocin (Exoginous)
2.Prostaglandins (PGE-2,PGF-2a,15-methyl PGF-2a
3.Ergot Alkaloids (Ergonovine)
Drugs That Delay Uterine Motility
1,. Magnesium sulphate;
2.b-2adrenergic agonists
3.Ca-2 blockers
4.Prostaglandin synthetase inhibitors..
Induction of Labour
In situation such as Diabetes Mellitus,Hypertension,Isoimmunization,Intrauterine growth defects,and placental defects the continuation of pregnancy may become risky to the mother or baby more than the delivery.
Before the pharmacological induction is carried out various things should be considered such as the fetal maturity,the fetal position,fetal distress,placental abnormalities,and previous uterine surgery.
The drug of choice for inducing labour is Oxitocin.A dilute solution of oxitocin can be infused intra venously as a slow infusion to induce a safe labour as 10 milliunits per ml.The procedure should be with gradual increase of the dosage by starting with 1 milliunit/ml and gradually increase for every 30 minutes and maintain at 4 milli unit /ml.for atleast 1 hr before bring it to the optimum dosage of 10 milliunit/ml
During the entire procedure trained persons must be engaged and uterine activities should be carefully watched.
It contractions are forceful and violent wih increased frequencies or alarm signals raised for a tired muscle cells the infusion of oxitocin must be immediately stopped.
Fetal discomfort can be easily estimated with its cardiac beats.
If there is a tetany like uterine contraction it should be relaxed by the use of a b-2 adrenergic agonist such as terbutalin.
To avoid undesirable side effects the terbutalin should be given as slow subcutaneous injection.
When the progression of labour becomes normal the rate of infusion of oxitocin should be minimised or stopped as per the need.The infusion should be maintained at the lowest possible rate inorder to maintain an adequate progression of labour.
When employed in term oxitocin induce labour in majority of cases.
Amniotomy the artificial ruputing of fetal membranes along with oxitocin can also be used to induce labour.These procedures should be done with experienced obstetricians to avoid fetal distress.
Augmentation of the Labour.
If augmentation of the labour proceeded normally in that case infusion of oxitocin is not necessry and should not be used.
In normal labour the force of normal contraction of the uterus should not be disturbed by drug induced augmentation as this will make incoordinaed force full contraction of the uterus against partially dilated cervix and may causes uterine rupture,severe laceration of the mother,trauma of the fetus,and a tetany like contraction may compromise the pacental exchange and a disconnection of oxigen supply to the fetus.
In case of dysfunctional labour the labour can be augmented by an experienced obstetrician by the oxitocin successfully.Bu an unjustified and careless use of oxitocin may itself induce dysfunctional labour.
Therapeutic Abortion
If pregnancy is dangerous to the mother aborting the baby is prescribed to save the mother by the doctors.
Suction curettage is the method usually employed by the doctors to induce abortion.
Mifepristone a 19-norsteroid a progesterone antagonist is usually employed in this method.Mifepristone when administered along with prostaglandin can induce 99%abortion at early pregnancy.Also in early pregnancy a combination of mifepristone along with methotrexate, and misoprostol can induce 96% abortion .
Beyond the first week of he second trimester there are so many options are available to induce abortion.Intra amniotic injection of a hypertonic sodium chloride (20%) are used with many failures and this produces follows several potential hazards of hypertonicity.
Vaginal suppositories of PGE-2 (Dinoprostone and Prosten E-2) has been inserted into the vigina with the intervals of 3 to 5 hours has been tried successfully.
In circumstances such as if still the uterine cantent are not eliminated completely but uterus is ruptured the intramuscular injection of 0.25 mg of carboprost tromethamine,a 15-methyle PGE-2a Hemabate) has been proved effective.Subsquent doses of 0.5 mg can be given with 2 hrs intervals.Nausea and vomiting are the side effects of these prostaglandins.
Intra vajinal suppostories of misoprostol also can be tried for every 12 hours.
After abortion whether its auto or induced abortion the bleeding should be controlled similar to normal labour procedures by ergonovine and oxitocin.
Delayed Labour
Drugs are used to delay the labour by inhibiting uterine contractions in the following situations:-
1.To prevent premature labour.
2.To carry out other therapeutic measures
Drugs that are used in this procedure are called as Tocolytic agents:-
1.Magnesium sulphate
2.b-2 adrenergic agonists
3.Calcium channel blockers
4.Prostaglandin synthetase inhibitors.
Some patients may well respond to bedrest to prevent early contractions of the uterus.If not only tocolytics should be tried.
The delayed labour should be equally weighed between its advantages and risks.In general the use of tocolytic agents are reserved for those pregnancies where the gestational age is greater than 20 weeks and less than 36 weeks.A child born within this range of pregnancy period is considered as premature.
Before starting the drug therapy a consideration must be made with a minimal dilating requirement of cervix is less than 4 cm.and cervical effacement(the thinning of the cervix) is less than 80%.
Contraindications to tocolytics 1.Rupture of uterine,cervical or amniotic membranes
2.Eclampsia,a condition in which convulsions occur in a pregnant woman with high blood pressure
3.Preeclampsia,a condition of eclampsia with organ damage such as kidney in high blood pressure.
4.Chorioamnionitis Infections of the fetal membranes the chorion and amnion.
5.Premature detachment of placenta
6.Fetal distress.
b-2 Adrenergic Agonists
1.Ritodrine (FDA approved to delay labour)
2.Terbutaline
Ritodrine hydrochloride(Utopar) is available for oral and i.v. injections
Ritordine HCl is slowly infused at the rate of 0.1 mg/min and if tolerated the rate is further increased by 0.5/min for 10 min and further increased to a maximum of .035 mg/min until labour is controlled.Once attained the controll the infusion is continued usually for 12 hrs at the rate attained.
Oral adminisration should be stared before 30 min of the termination of the infusion by 10 mg per every 2 hours for the first 24 hrs.followed by 10 to 20 mg per every 4 to 6 hrs.The total daily dose should not exceed 120 mg.
Terbutalin (Bricanyl) should be given orally 2.5 to 5 mg every 6 hrs and intra venously at 10 to 80 mic.gm/min and subcutaneosly at 0.1 to 0.4 mic gm /min for 1 to 4 hours.
