By Chioma Umeha
Assisted hatching (AH): A study in the
Reproductive Biomedicine Online found that the process of assisted hatching –
weakening the outer layer of the embryo before it is transferred to the uterus
– does not improve pregnancy and implantation rates in women who are having
fresh embryos transferred. The researchers noted, however, that women having
frozen embryos implanted do benefit from having their embryos treated in this
way.
How many embryos are transferred?
There are still differences in practice as to how
many embryos are transferred into the woman’s uterus. In many cases, only one
fertilized embryo is transferred to the uterus, while other doctors believe
that two fertilized embryos increase the chances of a successful pregnancy.
According to guidelines set out by the
International Journal of Gynaecology and Obstetrics, the number of fresh
embryos to be transferred varies according to the woman’s age and outlook. In
many cases, no more than two embryos will be used. For women under the age of
35 with an excellent chance of pregnancy, doctors will consider using just one
embryo.
A recent study posted in Fertility and Sterility
showed that single embryo transfer in women less than 38 years of age reduces
the risk of multiple births, yet does not seem to affect live birth rates. This
is important to note, as many doctors recommend using multiple embryos to
ensure pregnancy. This research indicates that multiple embryos may not be
necessary.
When the woman’s chances for pregnancy seem to be
low, doctors may opt to use a technique called heavy load transfer (HLT), in
which three or more embryos are transferred to the uterus. According to a study
in Facts, Views & Vision in Obgyn, HLT should be recommended in patients
with a poor natural outlook, as it is likely to boost pregnancy rates to an
acceptable level.
Success rates of embryo transfers
The rate of success for embryo transfers may vary
based on the transfer method used.
According to a study posted in the International
Journal of Reproductive Medicine, there is no statistical difference between
using fresh and frozen embryos. Embryo transfers using fresh embryos had a 23
per cent pregnancy rate, whereas frozen embryos had an 18 per cent pregnancy
rate.
The study showed that frozen embryos could also be
used for additional embryo transfers where fresh embryos could not. If the
chance for pregnancy is low, doctors may consider freezing additional embryos
for a second attempt at embryo transfer at a later date.
Individual success rates can vary and may depend
upon the cause of infertility, ethnic backgrounds, and genetic disorders.
