If you’re over about 5’8” and you’re undergoing in vitro fertilization (IVF), you may need to double up on baby supplies. A new study coming out of the recent annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in Stockholm found that taller women are more likely to have a twin pregnancy following a double embryo transfer during IVF. With increasing concern about the risks of multiple pregnancies (preterm birth, preeclampsia), more doctors are trying to determine when to transfer just one embryo (called single embryo transfer) and when to transfer more than one, and still enable a woman to deliver a healthy baby -- ideally just one -- after a round of IVF. This news may help fertility specialists strike a better balance. “This is a further step towards the development of tailor-made personalised IVF treatment,” said Dr. Marieke Lambers, from VUMC, Gynaecology Obstetrics and Reproductive Medicine, Amsterdam, in speaking at the conference.
Dr. Lambers and her colleagues looked at a variety of factors in nearly 20,000 women in the Netherlands who had undergone IVF between 1983 and 1995, including whether the woman had a single or multiple pregnancy, as well as their height, weight, body mass index, age when pregnant, number of eggs retrieved during IVF, and more. In crunching all the data, the researchers noticed something: “We found that a maternal height of over 1.74cm [about 5’8 ½”] and more than 11 [eggs] retrieved were independently associated with twin pregnancies,” said Dr. Lambers in a release. The higher number of eggs retrieved at least partially explains why the tall women were more likely to become pregnant with two babies instead of one, but the possible influence of greater height is less clear. A press release issued about the study offers one possible explanation: “Previous studies have shown that women who are prone to conceive twins after IVF have a higher level of vascular endothelial growth factor-A (VEGF-A), which promotes the growth of blood vessels at the site of implantation.” Dr. Lambers suggests that “perhaps there is also an association between tall stature and increased VEGF-A levels.”
Are you concerned about twins (or higher-order multiples) with IVF?