Multiple gestation

Definition
Multiple gestation or multiple pregnancy is defined as a pregnancy with twins, triplets, quadruplets or more. Rarely, a woman may carry up to seven or even eight babies at one time. The length of pregnancy generally decreases as the number of babies increases.

Causes/associated factors
A combination of processes can result in more than one fertilized egg. Identical twins (also called monozygotic or single-ovum twins) occur by chance. Identical twins are formed when a single fertilized egg divides. They may or may not share the same placenta (a structure in the womb that develops during pregnancy to nourish the fetus and help it discard waste), but typically have separate amniotic sacs (the sac that contains the amniotic fluid, which protects a fetus in the uterus). Identical twins are the same sex and have the same blood type, hair color and eye color.
Fraternal twins (also called dizygotic or double-ovum twins) occur when two eggs are fertilized. The occurrence of fraternal twins is influenced by several factors, including race, parity (carrying a fetus to a point of viability), the use of fertility drugs, and maternal heredity and age. Fraternal twins have separate placentas and amniotic sacs.

Triplets, quadruplets and higher-order multiples may arise from one or more eggs. They may or may not have separate placentas and amniotic sacs.


Signs/symptoms
If you have a multiple pregnancy, you may gain an excessive amount of weight compared to a pregnancy with only one baby. If you've been pregnant before, you may feel larger or notice more fetal movements than you did with an earlier pregnancy. Common pregnancy symptoms, such as pelvic pressure, abdominal distention, nausea, backache, varicose veins, difficulty breathing, constipation and hemorrhoids, may occur earlier and be more severe.
Your uterus may be larger than expected for your baby's gestational age. (In a twin pregnancy, the height of the uterus is usually 4 centimeters more than expected.) The doctor may hear more than one fetal heartbeat, which may be heard with a Doppler device late in the first trimester and a fetal stethoscope at about 18 to 20 weeks. He or she may also notice more than the expected number of fetal body parts when examining your abdomen by touch.

Some women who have multiple pregnancies develop anemia (a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron). Anemia is caused by increased blood volume, along with an increased need for iron and folate for the additional babies.


Diagnosis
In addition to the symptoms of a multiple pregnancy, your doctor may suspect a multiple pregnancy if you have a maternal family history of fraternal twins or you recently used fertility drugs. Early diagnosis is important to ensure the best care possible for you and your babies.
Most multiple pregnancies can be identified through a physical exam before the second trimester. If a multiple pregnancy is suspected, your doctor will do an ultrasound (a procedure in which sound waves are used to create an image of internal body parts) to help confirm the diagnosis. A transvaginal ultrasound can often identify a multiple pregnancy by four weeks after conception. When twins are confirmed through an ultrasound, a more thorough exam is done to determine the exact number of babies.

Blood tests cannot reliably diagnose a multiple pregnancy, but levels of human chorionic gonadotropin (hCG) and alpha-fetoprotein (AFP) in the blood are usually higher than you would expect with a single pregnancy.


Treatment
During a multiple pregnancy, you'll be monitored closely by your doctor to minimize the risk of complications through early detection of problems. This will require more frequent office visits and testing.
You'll need more iron and folic acid in your diet or through supplements. You'll also need to consume about 300 more calories a day than a woman with a single pregnancy. The American College of Obstetricians and Gynecologists (ACOG) recommends that a woman carrying twins gain 35 to 45 pounds. If you're underweight or carrying more than two babies, you may need to gain more.

Extra rest is also important. You may need to cut back on your work hours or stop working altogether. It's best to discuss your activity level with your doctor.

A routine ultrasound to assess fetal growth is often recommended during the second trimester. Weekly nonstress tests (a diagnostic test that helps doctors determine the response of a fetal heartbeat to fetal movement, spontaneous contractions or other stimuli) usually begin by week 36 or sooner. Your doctor may also examine your cervix frequently to ensure that it's not opening prematurely. If complications arise, your care may include bedrest, home uterine monitoring and medication to stop the contractions. More aggressive measures are used if preterm labor develops.

Whether you'll have a vaginal or cesarean delivery depends on your individual situation. It's best to deliver your babies in a hospital with the help of a staff experienced in multiple pregnancies. The delivery room will be equipped for an immediate cesarean section in case it becomes necessary. A pediatrician or neonatologist is often present as well.


Complications
Complications are more common in a multiple pregnancy. Prompt diagnosis and treatment are essential.
Possible complications include:

combined pregnancy (when one embryo is ectopic or implants itself outside the uterus)
anemia (a condition marked by a decreased number of red blood cells or hemoglobin, a protein in red blood cells that contains iron)
urinary tract infection
high blood pressure
preterm labor
abruptio placenta (early separation of the placenta from the uterus)
hydramnios (excessive amniotic fluid)
postpartum hemorrhage (excessive bleeding)
The average length of a multiple pregnancy is 37 weeks. About half of multiple pregnancies result in premature deliveries. The risk of preterm labor for a twin pregnancy is about seven to 10 times higher than a single pregnancy. Triplets tend to be born at about 32 to 34 weeks. With four or more infants, the overdistended uterus causes even earlier labor, often at about 30 to 31 weeks.

Rarely, delivery of one infant may be delayed or the babies may have a significant difference in weight. Additional rare complications for identical twins may include:

interlocked heads
being conjoined (Siamese twins)
placental vascular anastomosis (blood flow between the two fetuses through the placenta)
twin-twin transfusion syndrome (shunting of blood from one twin to the other)
fetal malformations due to poor oxygenation of blood
umbilical cord abnormalities, such as the absence of one umbilical artery
In some multiple pregnancies, one or more of the multiples may not survive.

To reduce the risk of complications, it's important to receive early and regular prenatal care. Take good care of yourself by following your doctor's recommendations for diet, activity and rest. Discuss the warning signs of complications with your doctor and seek appropriate care immediately. Attending a prenatal class on multiple pregnancy can also be helpful.