Ever since ancient times, there has been a great fascination with multiples. Twins, triplets, quadruplets and higher order multiple pregnancies have been reported throughout history. Even today, stories of women such as “Octomom” make the headlines and remain in the news.
There has been a dramatic increase in the number of multiple pregnancies in the United States and abroad since the start of assisted reproductive techniques such as in vitro fertilization in the 1970s. Traditionally, approximately one percent of live births were twins, with about one third of twins being identical and two thirds being fraternal. (Identical twins result from the splitting of a fertilized egg, while fraternal twins occur when two separate eggs are fertilized.) In the era of effective infertility treatments, the rate of twin pregnancies has increased to about 3 percent of live births, with about 90 percent of the twins being fraternal.
While being a twin can offer many advantages (as a twin, you’re never alone!), twin pregnancies face more challenges and complications than pregnancies involving a single baby. The most significant complication is premature birth. While the average single pregnancy delivers at 40 weeks or 280 days after the start of the woman’s last menstrual period, the average twin delivery occurs at 35 to 36 weeks’ gestation. Approximately 50 percent of all twin births are premature, with 15 percent of twins being born significantly preterm (at less than 32 weeks).
The main causes for prematurity in multiple pregnancies are preterm labor, incompetent cervix, preeclampsia and placental insufficiency. Preterm labor is when the uterus contracts prematurely to expel the fetuses. The more rapidly growing uterus of the multiple pregnancy appears to be prone to contract more frequently and earlier in gestation.
Incompetent cervix is when the cervix — which is the organ designed to hold the babies inside the uterus and prevent infection — abnormally shortens and dilates prematurely. This often leads to premature rupture of the membranes and delivery of the infants.
Preeclampsia is a disease of high blood pressure caused by pregnancy, which includes widespread but usually reversible injury to the mother’s blood vessels. Preeclampsia can involve many organ systems and often requires the ob/gyn to perform an early delivery of the fetuses to cure the mother and protect the babies.
Finally, with two or more mouths to feed, there may be a greater demand for nutrients and oxygen than the mother can provide the fetuses through the placentae. Sometimes multiple pregnancies deliver early when the ultrasound shows that one or more of the babies is not receiving an ad- equate amount of nutrients and/or oxygen.
Women pregnant with multiples should seek the prenatal care of a physician experienced with the issues involved in multiple pregnancies. The doctor will perform serial ultrasound examinations of the cervix in order to assess early cervical change, which might indicate a risk for preterm labor or an incompetent cervix.
If you are pregnant with more than one baby, frequent office visits are necessary for monitoring blood pressure and urine to screen for preeclampsia. Serial ultrasound measurements of the fetuses and fetal testing help assure that the babies are receiving the nutrients and oxygen they need in adequate amounts. Such surveillance techniques allow for early detection and possible treatment of preterm labor, incompetent cervix, preeclampsia or placental insufficiency.
While women with twin pregnancies face many challenges and an increased potential for complications, most twin pregnancies result in the birth of healthy children. As with so many things in life, preparation is key. In order to achieve the best outcome, it is important to make sure you are receiving the highest quality healthcare possible and that you make caring for you and your babies a priority.
Bruce F. Cohen, M.D., is the Division Director of Maternal Fetal Medicine at Beth Israel Deaconess Medical Center in Boston, MA, and an Assistant Professor of Obstetrics, Gynecology and Reproductive Medicine at Harvard Medical School.
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