Carrying twins increases the risk of pregnancy complications that can affect one or both babies or the pregnancy itself. Many irregular heartbeats resolve spontaneously before birth, but some serious conditions can cause an irregular heartbeat in one or both babies before birth. An irregular heartbeat in one of the babies might require further evaluation and possibly treatment even before birth.
Frequency
An irregular fetal heartbeat is a common finding, occurring in around 14 percent of all unborn babies, but irregular heartbeats cause problems for just 1 percent to 2 percent at birth, Yale researchers reported in the April 2000 issue of the "American Journal of Obstetrics and Gynecology." Of the eight of 1,000 babies born with a heart defect, only around 50 percent will need treatment, Dr. Charles Kleinman reports in the "Yale University School of Medicine Heart Book." Twins do not necessarily have the same genetic makeup or the same prenatal development, so one and not the other might have a heart defect.
Diagnosis
Your doctor will listen for both heartbeats during examinations, but sometimes it's hard to make sure you're not listening to the same baby's heartbeat twice. External fetal monitoring can trace two separate heartbeats at the same time so that your doctor is sure she's actually hearing both. A level II fetal ultrasound also can show exactly which twin has an irregular heartbeat. Fetal echocardiography can show whether any abnormalities are present in the heart.
Causes
Many things can cause an irregular heart in one or both twins. If you have identical twins, a condition called twin-to-twin transfusion develops in around 10 percent to 15 percent of cases, according to the University of California, San Francisco. This occurs only when both babies share a single placenta. Blood flow to one twin increases while the other doesn't get enough, causing one baby to grow and the other to have little growth. Either baby might develop heart failure, with abnormal heart rhythms, although the baby with too much blood normally shows signs of this first. Heart defects can occur early in pregnancy when the heart first forms in one or both babies.
Treatment
If one twin has a known irregular heartbeat, special care can be taken right after birth to further diagnose and treat the problem. Doctors who specialize in newborn heart problems or neonatologists who deal with general problems of newborns might be present right in the delivery room to ensure prompt treatment if needed. In the case of twin-to-twin transfusion syndrome, laser surgery during before birth can severe the abnormal connection between the two babies, giving both a chance to grow normally. Success rates of survival of one baby at 76 percent and 36 percent for both are common, UCSF reports.
References
- UCSF; Twin to Twin Transfusion Syndrome; Febrary 2011
- "American Journal of Obstetrics and Gynecology"; The Clinical Significance of the Irregular Fetal Heart Rhythm; Joshua Copel, M.D., et al.; April 2000
- "Yale University School of Medicine Heart Book"; Chapter 20: Heart Disease in the Young; Charles Kleinman, M.D.
- Yale Bulletin and Calendar; Study Confirms Irregular Fetal Heartbeats Are Not a Cause for Panic; April 2000
