How Many Embryos Should One Transfer: The IVF Dilemma

It is common knowledge that assisted reproduction methods, such as intrauterine insemination (IUI) and in vitro fertilization (IVF), when successful, often result in multiple pregnancy. Some wonna-be-moms, in fact, want to have twins or triplets, especially those who have tried to conceive for a long time—after all, having more than one baby at the same time seems to compensate for the many months or years lost in waiting. Doctors, however, frown at such possibilities. The optimal outcome of an assisted reproduction, they say, is a singleton pregnancy.

With the advances of modern-day assisted reproduction technologies, one does not need to transfer three or four embryos in order to increase the patient’s chance to get pregnant. The concern, nowadays, has shifted to the opposite side of the spectrum. Doctors are now more concerned with the need to perform fetal reduction in the event of pregnancy with multiple fetuses.

The problem is not necessarily with the obvious inconveniences of being pregnant with more than one baby. True, one’s morning sickness will be amplified many times over, making a woman’s first trimester a hardly tolerable experience. Carrying more than one baby in the later months of one’s pregnancy can also be an ordeal. The weight an expectant mother of twins or triplets gains during pregnancy is often significantly greater than the pregnancy weight gain of women carrying a single baby. The exhaustion and backache are much intensified. Finding well-fitting maternity clothes is also a problem.

The true concern, however, lies with the babies’ and mother’s health. The mother is at a high risk of developing gestational diabetes and preeclampsia. Placental function has an increased probability of being abnormal, reducing the amount of oxygen and nutrients reaching the fetuses. Twin-twin transfusion, in which blood flows from one fetus to the other through the shared placenta, is a life-threatening condition that should be considered in the case of identical twins. The risk of miscarriage is also elevated—roughly one out of three multiple pregnancies fail. Of those that continue, many do not last 36 weeks and end with cesarean section.

Premature birth may result in severe complications or death of the newborn (often due to brain damage or immature lungs) and typically necessitates the baby (or babies) to remain under intensive care for weeks as the baby’s heart, brain, lungs, intestines, or eyes may have not fully developed. The cost of the care is often in the six figures. More importantly, however, the chance of living with a disability (at least during the childhood years) increases in inverse proportion to the birth weight of a baby. (Roughly a quarter of the neonates who weigh less than two pounds experience some sort of disability.)

That said, the majority of twins and triplets do survive and develop into healthy children. With close monitoring during the pregnancy, appropriate nutritional choices, and increased rest, many women manage to carry multiple fetuses to term. It is all about the risk one is willing to face. In the end, even though transferring multiple embryos can increase one’s chance to conceive, it also jeopardizes one’s chance of having a complication-free pregnancy and a healthy child.

The best solution modern-day IVF technology offers is the ability to screen embryos for chromosomal and/or genetic abnormalities before an embryo transfer occurs. A single healthy embryo has a much higher chance of leading to a successful pregnancy than two or three embryos with unknown chromosomal count. To learn more about the screening procedure and its benefits, visit my post “Preimplantation Genetic Screening (PGS): Why You Should Do It.”