Review article
MULTIPLE PREGNANCIES AFTER IN VITRO FERTILIZATION
Miro Kasum
; Klinika za ženske bolesti i porode Medicinskog fakulteta u Zagrebu i KBC-a, Petrova 13, Zagreb
Abstract
Since the first pregnancy after in vitro fertilization and embryo transfer (IVF-ET) over a million pregnancies have been achieved worldwide by IVF and its modifications. On a per–cycle basis, the results of IVF are similar to the fecundability of natural conception cycles in the general population. The cumulative success rate is higher when IVF is attempted on a repetitive basis. Pregnancy rates have consistently improved over time. By 2002, the delivery rate per retrieval was 32%. However, the incidence of twins and high order multiple pregnancies (ie. triplets or more) has risen over the past two decades. From 1980 to 1997, the annual number of live born babies from twin gestations rose 52%, while the number of high order gestations increased 404%. This rise was mainly due to increased use of fertility drugs for ovulation induction, superovulation, and IVF. In the USA, 1997 data showed that approximately 18% of high order gestations were spontaneous, 38% due to ovulation induction procedures, and 43% attributable to IVF. Compared to natural ovulation and conception, IVF increases the chance of having twins 20-fold and triplets/quadruplets 400%. Often, infertility patients consider the birth of twins acceptable, or even desirable, since it results in an family increase after years of infertility. A number of studies have reported an increase in the adverse perinatal outcome of pregnancies obtained with IVF-ET. Multiple gestations are at increased risk of fetal, neonatal, and maternal complications, as well as complete pregnancy loss, when compared to singleton pregnancies. Neonatal complications are primarily the result of preterm delivery. Several strategies attempting to control the frequency of high order multiples have been implemented. The overriding aim of these strategies is to transfer fewer embryos of higher quality to maximize the pregnancy rate and to minimize the risk of high order multiple gestation. National legislation in several European countries has proven to be more effective in reducing the high order pregnancy rate than practice guidelines in the USA. Maternal age is important because women under age 35 achieved excellent birth and multiple gestation rates with trensfer of two embryos, while women over 35 years of age required transfer of three embryos to achieve similar results. The ability to select only the highest quality embryos would allow transfer of fewer of them achieving acceptable birth rates. Day 5 transfer (blastocyst stage) of only one or two blastocysts need to be transferred to maintain overall success rates while decreasing the high order multiple pregnancy rate. Utilization of single embryo transfer will likely increase as method of predicting embryo viability and to reduce high order pregnancy mounts. Strategies to reduce the high order multiple gestation rate start from ovulation induction including close monitoring of follicle development, a strict cycle cancellation policy and aspiration of supernumerary follicles. After multifetal pregnancy reduction, pregnancies with three or less fetuses have fewer pregnancy losses, increased gestational age, and higher weight. Selective termination has been established as a safe and effective means for termination of one or two abnormal fetuses.
Keywords
multiple pregnancies; in vitro fertilization; outcome of pregnancy; fetal reduction
Hrčak ID:
65709
URI
Publication date:
1.3.2009.
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