This article is for information and overview purposes only and does not represent every possibility or situation. If you are concerned about any aspect of your pregnancy, please consult your doctor as affects your particular situation.
The use of diagnostic ultrasound imaging has made it possible to determine as early as five or six weeks that Mom is pregnant. Ultrasound (US) picks up the fetal heartbeat(s) allowing the medical team to also determine how many fetuses are present. In some cases, two or more fetal heartbeats can be found leading to excitement and some trepidation for the expecting parents. The use of US to determine pregnancy at such an early stage, however, has also identified another issue which might occur known as Vanishing Twin Syndrome (VTS).1 For women experiencing VTS, during a subsequent US (up to about 12 weeks gestation), one or more fetal heartbeats may no longer be found. The empty sac may, or may not, be visible on the screen.
In years past, women had their first US after the 12th week of gestation therefore eliminating the possibility of knowing that they were initially carrying more than one fetus. The availability of US as early as the 5th week of pregnancy has allowed researchers to conclude that the rate of multiple-birth conception is much higher than previously thought. It is estimated that one in eight people may have started as a twin, but only one in seventy pregnancies actually resulted in a twin birth.2 VTS usually has no symptoms, but sometimes a pregnant woman might have unexplained bleeding, cramping or passage of tissue in the week(s) in her first 12 weeks of pregnancy. Such symptoms could indicate the loss of a multiple pregnancy, a blighted ovum, or in some cases nothing at all. Not all cases of VTS are associated with any outward signs and many women continue with an uncomplicated pregnancy and the birth of a healthy child(ren).
VTS does not just occur with twin pregnancies, but can occur within higher order multiple sets as well. The loss of one, or more, embryo in the first trimester can be emotionally devastating for expecting parents. For example a couple was 8-1/2 weeks pregnant with triplets when they registered for a multiple-birth prenatal class. When they arrived for the class at just over 13 weeks pregnant, they advised that a subsequent ultrasound had shown that they were now carrying two babies, and an empty sac had been visible on their latest ultrasound. The couple had a difficult time because two other couples in the group were carrying triplets and they realized they were no longer part of that special group. In such cases, referral to counseling may assist expecting parents in dealing with their early fetal loss and allowing them to celebrate in their continuing pregnancy.
Risk factors for experiencing VTS are generally unknown but seem to include a maternal age over 30. If the vanishing fetus occurs in the first trimester, as it does in most cases, no medical intervention is usually necessary. The mother, the placenta or the surviving co-multiple may absorb any miscarried fetal tissue within a few days.
VTS does not generally affect the ability of a woman to conceive again, although there could be underlying genetic or health issues that should be explored with a physician.
While VTS usually poses no problem physically for the mother or the surviving child(ren), it is not uncommon for mothers to have feelings of disappointment, grief and loss as they had anticipated and looked forward to a multiple-birth.3 As the pregnancy continues with at least one healthy child, these mothers may be told that the loss isn’t important or to focus on their healthy baby. It can be difficult for mothers to find acceptance or a safe place to grieve this loss as family and friends fail to understand that a unique parenting experience has also been lost as well as a much-wanted child. Women and their partners experiencing VTS are encouraged to seek counseling if feelings of depression, sadness, or anxiety continue. Local and national parenting support groups may offer networking opportunities for parents who have suffered from VTS.
Vanishing Twin Syndrome (VTS), Part 1
1) De la Fuente, G., Puente, J., Garcia-Velasco, J., & Pellicer, A. (2011). Multiple pregnancy vanishing twin syndrome. In Biennial Review of Infertility (pp. 103-113). Retrieved from http://link.springer.com/chapter/10.1007%2F978-14419-8456-2_9?LI=true
2) Heim, S. (2007) It’s Twins! Charlottesville, VA: Hampton Roads Publishing.
3) American Pregnancy Association. (2007). Vanishing Twin Syndrome. Retrieved from http://americanpregnancy.org/multiples/vanishingtwin.html
Mothering Multiples, by Karen Kerkhoff Gromada, La Leche League International
The Art of Parenting Twins, by Patricia Maxwell Malmstrom and Janet Poland, Ballantine Books
Twins! Pregnancy, Birth and the First Year of Life, by Connie L. Agnew, Alan H. Klein and Jill Alison Ganon, Harper Perennial