Most IVF programs in 2021 are performing frozen embryo transfers rather than using fresh embryos.
Frozen embryo transfers require that the uterus be prepared first in order to allow
embryo implantation. The method used to prepare the uterine lining involves the patient taking
estrogen to make the uterine lining thicker followed by progesterone to transform the lining
so it is receptive to an embryo. There has been a lot of research which indicates that
the number of days that progesterone is given is important for optimizing IVF success.
What about the number of days of estrogen? Does that matter? Let's take a look.
This is the protocol for a typical frozen embryo transfer treatment. A woman calls with her period.
A few days later, we perform a baseline blood test and ultrasound. We are looking to make
sure that the patient’s estrogen and progesterone levels are low and that the uterine lining looks
normal. If everything looks good, the patient is started on estrogen. At IVF1, we typically
start with oral estrogen but vaginal estrogen, estrogen patches or injections can also be used.
Several days later, the patient returns for blood testing and ultrasound. We would like to see that
the estrogen levels in the blood have started to go up and the progesterone levels have stayed low.
We would also like to see that the uterine lining has gotten thicker. At a certain point,
when the doctor has determined that the lining is ready, the patient will be started on progesterone
and the embryo transfer is scheduled. For top IVF programs like ours that transfer
blastocysts, the embryo transfer is typically scheduled on the 6th day of progesterone.
The number of days needed for the estrogen part of the preparation is going to vary
based on how quickly the patient’s uterine lining gets thicker and the availability of the patient,
the doctor and the IVF lab. The length of time for progesterone
is usually going to be the same 6 days.
Is there an optimal number of days to have a patient take estrogen
before beginning the progesterone? In other words,
is it better to have less days of estrogen or more? Does it even matter?
To answer this question, we looked at the data from my patients at the Naperville Fertility
Center. To maximize our pregnancy rates, all patients at our center get frozen embryo transfer.
To minimize the risk of multiple pregnancy, everybody has a transfer of a single embryo.
So far in 2021, I have performed over 300 embryos transfer. To prevent skewing the results,
I analyzed only the first embryo transfer for each patient during that time. Ultimately,
we looked at 253 embryo transfer cycles. We divided the patients so that we would
get roughly equal numbers of patients in each group. There were four groups.
Group one were patients who had 9 or 10 of estrogen before starting progesterone.
Group 2 had 11 days. Group 3 had 12 days and Group 4 had 13 or more days.
Question #1. Did the number of days of estrogen impact the chance that the embryo would implant?
There wasn't any significant difference in the percentage of patients who had a positive
pregnancy test eight days after the transfer. This was true when we looked at all of the patients
and those patients who had transferred embryos
that were tested for chromosome abnormalities which is called PGT.
Question #2. Was there a different in the risk for miscarriage?
We monitored pregnant patients initially with blood tests and eventually with ultrasounds.
We followed them until we were able to see a fetus with flickering heart motion
on ultrasound at least twice. This is called an ongoing pregnancy. Since most miscarriages
occur before this, it is the point we usually send our patients back to their obstetrician.
The miscariage did not show any particular trend based on the number of days estrogen was given.
Our InfertilityTV bottom line is this. There does not appear to be any impact
of the length of time that estrogen is given in frozen embryo transfer cycles. Frozen embryos
transfers can be scheduled once the lining is found to meet the criteria of the IVF
program and to accommodate the needs of the patient and program