time to plan remedial action. Because most cases of cervical stenosis have no indicative history (as in Case History 3), some IVF units perform mock ET as a routine in all cases [10].
Cervical dilatation
In cases of confirmed cervical stenosis, mechanical dilatation of the cervix under general anesthesia has been tried to make subsequent ET easier. This has been tried either as an interval procedure (at the start of the IVF cycle) [6,11], or at the time of the oocyte retrieval [4,12]. Both have been associated with easier subsequent ET, but only interval dilatation has led to improvement in pregnancy rate, perhaps because it allows sufficient time for the endometrium to recover from any trauma, inflammation or bacterial contamination resulting from the dilatation at the time of oocyte retrieval [13].
Other reported methods involve the use of osmotic cervical dilatation. These include the use of hygroscopic cervical rods (Dilapan) inserted in the cervix for 4 hours early (day 4) in the stimulation phase [14], and the use of intracervical laminaria tents for 24 hours – either at oocyte retrieval [5] or early in the stimulation phase [13]. All have been associated with easier ET and pregnancies, but the reported numbers are too small to allow for a meaningful comparison amongst different methods. These methods allow cervical dilatation on an outpatient basis without the need for general anesthesia.
Transmyometrial embryo transfer
An alternative method to transferring embryos through the cervix is transmyometrial embryo transfer (TMET), also known as the Towako method [15–18]. The technique is performed under transvaginal ultrasound guidance (see Chapter 65) and is not too dissimilar to oocyte retrieval. A special needle (Towako Needle Set, Cook IVF, Queensland, Australia) with its stylet attached to the vaginal probe needle holder is inserted transmyometrially and guided into the endometrial cavity. The stylet is removed, and a transfer catheter loaded with embryos is passed through the needle [18].
Despite concern about possible trauma to the endometrium, the pregnancy rate following TMET is similar to that with easy transcervical transfer [15–17]. The advantages of TMET include the ability to transfer embryos regardless of the severity of cervical stenosis, such as cases of post radical trachelectomy (Case History 2) [19,20]. It could also be performed with minimal or no sedation and provides an immediate solution to cases of cervical stenosis discovered for the first time at ET [18]. However, it requires special expertise and catheters that may not be available in every center.
Tubal embryo transfer
In cases with normal tubes, the embryos could be transferred through the fimbrial end of the fallopian tubes [21]. However, this requires laparoscopy and general anesthesia.
Hysteroscopic canalization of the cervix
In refractory cases, it has been reported that operative hysteroscopic shaving of the cervix to create a new canal could be used [7]. However, this method risks altering the structure of the cervix and may predispose to cervical weakness in a subsequent pregnancy. Therefore, it should be reserved for cases associated with amenorrhea or significant dysmenorrhea due to cervical stenosis.
Postponing ET
If cervical stenosis is discovered at ET, and facilities or expertise were not available for immediate remedial action (such as TMET), then it is far better to postpone the transfer than persist with a difficult procedure. If the attempted transfer was performed on day 2 or 3 post–oocyte retrieval, then it could be postponed till day 5 or 6 [22]. This gives time to implement suitable steps to facilitate ET. Alternatively, the embryos could be cryopreserved for later transfer, allowing plenty of time to prepare. The aim should be an easy transfer, now or later.
Key points
Challenge: Patient with cervical stenosis presenting for IVF.
Background:
Cervical stenosis occurs in about 1% of cases presenting for IVF.
Some are associated with severe dysmenorrhea or even amenorrhea, but most are asymptomatic.
Could be caused by DES exposure in utero or previous cervical surgery but most are of unknown etiology.
Management options:
Take history of previous cervical surgery or difficult or painful cervical instrumentation.
Perform mock ET to identify cases and plan action.
Cervical dilatation at the start of the IVF cycles will make ET easier and increase the pregnancy rate.
Cervical dilatation at the time of oocyte retrieval makes ET easier but does not seem to increase the pregnancy rate.
Transmyometrial ET could overcome the most difficult or impossible cases as it bypasses the cervix and leads to a pregnancy rate similar to easy transcervical transfer.
Tubal ET is an alternative in cases with normal fallopian tubes but requires laparoscopy and general anesthesia.
Hysteroscopic canalization of the cervix has been reported but should only be reserved for cases associated with amenorrhea or significant dysmenorrhea due to cervical stenosis.
Answers to questions patients ask
1 Q1 Why is my embryo transfer difficult? A1. The canal that leads into the cavity of your womb (called the cervix or the neck of the womb) is very tight. This is rare and occurs in 1 out of every 100 women and doesn’t harm your health in anyway. It just can lead to difficulty in embryo transfer, but there are steps we can take to overcome that difficulty. It may result from previous surgery but in most case no cause is known.
2 Q2 I had surgery on the cervix for abnormal smears and was told that it may make my embryo transfer difficult. Will this affect my success rate and what are you going to do about it? A2. In some case surgery on the cervix can lead to narrowing, which can make embryo transfer difficult. A difficult embryo transfer can reduce the chance of pregnancy, and that is why we need to be prepared. Before you start your IVF treatment, we will do a “trial” embryo transfer, when we will try to pass the embryo transfer catheter (a small plastic tube) through the cervix, just like the real thing but without embryos. If that goes well, then your embryo transfer will be easy. If we encounter any difficulty, then we will plan how to overcome it, either by dilating the cervix or using a special transfer catheter. That way, when we get to the real embryo transfer, we will be ready, and your transfer will be easy.
3 Q3 What will happen if my embryo transfer turns out to be difficult on the day of the treatment? A3. We will try using different catheters or techniques to make it easy, but if we couldn’t, we will freeze the embryos and then work out a plan to overcome the tight cervix (which may involve dilating it or using special catheters) and then do the embryo transfer on a later date. Studies have shown that the pregnancy rate from frozen embryos is as good as fresh embryos. Our aim is to give you the highest pregnancy rate through an easy transfer, and if that could not be done on the planned date, then it is better to freeze the embryos.
References
