The number of twin, triplet, and other multiple births has been increasing during the last two decades. As many as 1 of 30 deliveries involves more than one fetus.
The following make women more likely to become pregnant with more than one fetus:
Taking fertility drugs
Using assisted reproductive techniques Assisted Reproductive Techniques Assisted reproductive techniques involve manipulating sperm and eggs or embryos in a laboratory (in vitro) with the goal of producing a pregnancy. (See also Overview of Infertility.) If treatment... read more (such as in vitro fertilization)
Having had a pregnancy with more than one fetus
Being of West African descent
Carrying more than one fetus increases the risk of problems.
Carrying more than one fetus overstretches the uterus, and an overstretched uterus tends to start contracting before the pregnancy reaches full term (preterm labor Preterm Labor Labor that occurs before 37 weeks of pregnancy is considered preterm. Babies born prematurely can have serious health problems. The diagnosis of preterm labor is usually obvious. Measures such... read more ). As a result, the babies are usually born prematurely and are small. Risk of stillbirth Stillbirth Stillbirth is death of a fetus after 20 weeks of pregnancy. Pregnancy complications are problems that occur only during pregnancy. They may affect the woman, the fetus, or both and may occur... read more or death is increased for premature babies Premature Newborn A premature newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, premature newborns have underdeveloped organs, which may not be ready to function outside... read more . In some cases, the overstretched uterus does not contract well after delivery, causing bleeding in the woman after delivery (postpartum hemorrhage Excessive Uterine Bleeding at Delivery Excessive bleeding from the uterus refers to loss of more than 2 pints of blood or symptoms of significant blood loss that occur within 24 hours of delivery. After the baby is delivered, excessive... read more ).
Because the fetuses can be in various positions and presentations, vaginal delivery can be complicated. Also, the contraction of the uterus after delivery of the first baby may shear away the placenta of the remaining baby or babies. As a result, the baby or babies that follow the first may have more problems during delivery.
Carrying more than one fetus also increases the risk of problems for the woman. They include
Doctors suspect more than one fetus when the uterus is larger than expected for the length of the pregnancy. Ultrasonography Ultrasonography Ideally, a couple who is thinking of having a baby should see a doctor or other health care practitioner to discuss whether pregnancy is advisable. Usually, pregnancy is very safe. However,... read more is done to confirm the number of fetuses.
Because problems can result from multiple births, doctors may decide in advance whether to deliver twins vaginally or by cesarean.
If the first twin's position is normal Abnormal Position and Presentation of the Fetus Position refers to whether the fetus is facing rearward (toward the woman’s back—that is, face down when the woman lies on her back) or forward (face up). Presentation refers to the part of... read more (head first and facing the woman's back), the first twin is usually delivered vaginally. The second twin, if not in an abnormal position or in distress Fetal Distress Fetal distress refers to signs before and during childbirth indicating that the fetus is not well. Fetal distress is an uncommon complication of labor. It typically occurs when the fetus has... read more , can usually be delivered vaginally. If the first twin is in an abnormal position Abnormal Presentations Position refers to whether the fetus is facing rearward (toward the woman’s back—that is, face down when the woman lies on her back) or forward (face up). Presentation refers to the part of... read more or if the second twin in an abnormal position or in distress, cesarean delivery Cesarean Delivery Cesarean delivery is surgical delivery of a baby by incision through a woman’s abdomen and uterus. In the United States, up to 30% of deliveries are cesarean. Doctors use a cesarean delivery... read more is used. For triplets and other multiple births, a cesarean delivery is usually done.