There is one phenomenon that has always puzzled me. How can you get an ectopic pregnancy after IVF, if the point of IVF is that the embryo is replaced in the uterus, bypassing the fallopian tubes completely?
Usually, in a regular conception, the egg and sperm meet in the fallopian tube. The embryo then has to travel down the tube (Day 3) and into the uterus (Day 5). This is part of why Day 5 embryo replacements in IVF are considered more natural to the uterus.
Ectopic pregnancy occurs when a woman's egg is fertilised by her partner's sperm and the resulting embryo implants somewhere outside the woman's womb, usually in the fallopian tube, but sometimes even near the ovaries, abdominal cavity or the cervix. When an embryo grows outside the womb, a potentially life-threatening situation is created for both mother and foetus — the danger is the affected organ will rupture and cause severe bleeding.
Generally, an embryo cannot survive an ectopic pregnancy, and therefore treatment nearly always requires the removal of the embryo. Even if the ectopic pregnancy is not treated, the embryo will probably not survive, although the decision not to treat the ectopic pregnancy is a highly risky one for the mother.
Health statistics show that approximately 1% of all pregnancies are ectopic. Although ectopic pregnancies can occur also when a woman conceives naturally, fertility treatments such as IVF or IUI increase a fertility patient's chances of her pregnancy being ectopic by approximately 2.5–5-fold compared with natural conceptions.
How is this possible, that IVF increases the chances of ectopic pregnancy, since it bypasses the fallopian tube altogether?
Fertility specialists believe that ectopic pregnancy may occur if, when the embryos are transferred to the womb, they are placed too high in the womb cavity. The embryos then have a greater chance of "wandering" and implanting themselves in places where they are not supposed to be, such as the fallopian tubes. Embryos could also make their way into the fallopian tubes if they are injected into the womb with too much force.
In IUI, the risk of pregnancy developing in the fallopian tubes or elsewhere is increased if the sperm is injected with too much force, or placed too high in the womb cavity.
Some believe that embryo migration up into the fallopian tubes occurs because of local cellular activity or fluid mechanics present inside the uterus. Sometimes the opening of the fallopian tube in the uterus is dilated because of disease, making it easier for the embryos to enter the tubes. The process of IVF stims may increase the contractions in the uterus and, by doing so, force the embryo up and into the fallopian tube. This is called reflux expulsion of the embryo from uterine contractions.
There is a much higher risk of an ectopic developing in a blocked or scarred tube (if you have one), because the tube is not healthy and not strong enough to contract, and to be able to squeeze the embryo back into the uterus.
Between 2 and 5% of IVF treatments result in ectopic pregnancy, but the figure has been declining. For the past several years, embryo transfer has been routinely performed using ultrasound to properly guide the embryo catheter to the optimal uterine location, which may help to reduce the risk of an ectopic pregnancy. However, even ultrasound-guided embryo transfer cannot eliminate the possibility of an ectopic pregnancy after IVF.
How do you know if you are having an ectopic pregnancy? First, the HCG betas will rise, but very slowly, as the amount of HCG produced by the developing foetus will be significantly reduced. The HCG beta may rise and fall in a non-linear pattern. Second, at 6 weeks, the scan will reveal no gestational sac in the uterus. The doctor would have to search to find where the ectopic is and treat it — if you have these symptoms, you must consult a medical professional quickly.
Other than luck and a quiet uterus, are there any other factors which may make an ectopic pregnancy more likely? Does a transfer of a 5 day blastocyst make it more likely to embed in the uterus and therefore have a lower incidence of ectopic pregnancy? The idea is that decreased uterine contractility further along in the luteal phase would suggest that the ectopic pregnancy rates should be reduced after a day 5 transfer compared to an earlier cleavage stage transfer. The larger size of the blastocyst may decrease the chances that the day 5 embryo would migrate through to the fallopian tube.
Unfortunately, this is inconclusive. One study from 2003, which controlled for the mean BMI and tubal damage incidence of both groups, showed that 3.5% of day 3 transfers were ectopic and 3.9% of day 5 transfers were ectopic, hence the differential is not statistically significant.
A second study from 2011 showed that the incidence of ectopic pregnancy was 2.1% among day-3 pregnancies and 1.6% among day-5 pregnancies. The adjusted risk ratio for ectopic pregnancy from day-5 compared with day-3 transfer was 0.71, but the conclusion was also that one could not demonstrate a difference in the risk of ectopic pregnancy among day-3 compared with day-5 transfers.
If uterine contractions are caused by IVF stims, is it therefore possible that a FET transfer would reduce your rates of ectopic pregnancies as compared to fresh transfers, directly after stimulation? Unfortunately, it seems that uterine contractions can happen anytime. This study from 2012 showed that 0.47% of the fresh transfers had ectopic pregnancies, and 0.34% of the FET transfers had an ectopic. The difference between them was not statistically significant.
