UTERINE RECEPTIVITY
Successful pregnancies require that the embryo comes into
contact with the lining of the uterus (endometrium),
attach and eventually invade the uterine wall. There is
only a narrow window
of implantation during the menstrual cycle when the
uterus is receptive for an embryo establish a pregnancy.
This window of implantation opens six days after ovulation
and closes four days later.
For approximately fifty years, one approach to evaluate
uterine
receptivity has been with endometrial biopsies. Two
abnormal biopsies in a row have been classified a luteal
phase defect. Unfortunately, no studies demonstrate
that women with luteal phase defects have a lower chance
of establishing a pregnancy or a higher risk of miscarriage.
Endometrial biopsies, therefore, have been done for traditional
reasons only. It is our opinion that they provide no useful
information in the workup of unexplained infertility.
Another approach to evaluate uterine receptivity is to measure
blood levels of progesterone
around cycle day twenty-one. Levels greater than 10 ng/ml.
have been associated with normal corpus
luteum function, and by inference normal uterine receptivity.
Dr. Castelbaum and colleagues have published many of the
landmark studies using endometrial integrins as markers
of uterine receptivity. One marker, the avb3 endometrial
integrin has been extensively studied. It abruptly appears
in the lining of the uterus on cycle day 20, coincident
with the opening of the window of implantation. Many causes
of infertility result in diminished uterine receptivity.
Minimal and mild endometriosis,
blocked fallopian
tubes (hydrosalpinges),
unexplained infertility, polycystic
ovarian disease, and recurrent miscarriage patients
have diminished avb3 integrin levels, and thus decreased
uterine receptivity. Interestingly, when hydrosalpinges
are removed laparoscopically prior to in
vitro fertilization, normal uterine receptivity is restored.
It is our practice to offer hydrosalpinx removal prior to
IVF in women with blocked fallopian tubes. Women who do
not ovulate due to polycystic ovarian disease, hypothalamic
amenorrhea and premature menopause
can be easily treated with medications to create a receptive
endometrium. This is critically important for successful
frozen embryo transfers and for women using donor
eggs.
