Reduction is a special medical procedure intended for mortification and removal of one or several transferred embryos from the uterus. This procedure is suggested if multiple pregnancy is seriously dangerous for mother or future children’s health. After reduction embryo tissues remain in the uterus and in few weeks resolve on their own.
For the first time, reduction was used nearly 30 years defining serious pathologies of the embryos. Then it became a method of removal “excess” embryos using IVF to decrease risk of various complications like:
loss of all embryos;
further pathologies of development;
mortality of the second (third) child while childbirth.
Embryo reduction is quite a complicated procedure which is conducted by several indications:
implantation of three or more embryos into the uterus;
defining several pathologies of one or more embryos;
mother’s weak health or impossibility to bear 3 or more children.
In such a case, a patient have to sign a written agreement for conduction of such a procedure.
Embryo reduction while multiple pregnancy might be conducted during the 5-13th weeks of the pregnancy, but the most favourable time is the 8-9th weeks. The reason is quite clear. At the early terms of pregnancy one or few embryos might stop their development and disappear on their own (such a known “syndrome of the disappeared twin”). On the other hand, at the later terms reduction is possible but undesirable as fetus’ bone remains will resolve much longer and, in such a way, causes miscarriage.
Selection of embryos for reduction depends on several criterias:
pathologies of development;
the lowest indications of coccygeal-parietal size (in other words, fetus is less developed);
pathological size of nuchal space;
convenient access to the embryo excluding the contact with other embryos.
Besides, fertility specialist estimates the conditions of rest embryos taking into account their peculiarities of implantation, structure of fetal eggs, presence of yolk sacs, defines thickness of chorion.
Embryo reduction might be conducted in three ways using:
Transcervical method (through the cervical canal of uterus).
In such a case, reduction is conducted at the early terms of pregnancy (5-6th weeks) by the special catheter (attached to the vacuum-aspirator) which is indicated through the cervical canal. Under the US control, catheter is leaded to the fetal egg and destroy the embryo. There is no need of narcosis. Transcervical method of reduction has some significant disadvantages:
any injury of neck of uterus might cause miscarriage;
only fetal eggs nearest to the “exit” might be destroyed;
high possibility of ingress of vagina microflora through the cervical canal into the uterus;
That’s why, transcervical method is used very seldom.
Reduction is performed on the 7-8th week of pregnancy under general anaesthetic and control of ultrasonic transducer using bioptic adapter which needles the uterine wall. Then it’s introduced into the embryo’s chest and injected solution of chloride potassium till the complete heart activity. The main advantage of this method – minimal risk of injuries for the rest embryos.
Unlike transvaginal method, needle is introduced through abdominal wall at the 8-13th weeks of pregnancy. Reduction is conducted under the local anaesthetic and US control. Transabdominal method allows to choose any embryo for reduction.