Multiple pregnancy is a pregnancy with two or more fetuses. Names for these include the following:
- Twins – Two fetuses
- Triplets – Three fetuses
- Quadruplets – Four fetuses
- Quintuplets – Five fetuses
- Sextuplets – Six fetuses
- Septuplets – Seven fetuses
While multiples account for only a small percentage of all births (about three percent), the multiple birth rate is rising.
Multiple pregnancy usually occurs when more than one egg is fertilized and implants in the uterus. This is called fraternal twinning and can produce boys, girls, or a combination of both. Fraternal multiples are simply siblings conceived at the same time. However, just as siblings often look alike, fraternal multiples may look very similar. Fraternal multiples each have a separate placenta and amniotic sac.
Sometimes, one egg is fertilized and then divides into two or more embryos. This is called identical twinning and produces all boys, or all girls. Identical multiples are genetically identical, and usually look so much alike that even parents have a hard time telling them apart. However, these children have different personalities and are distinct individuals. Identical multiples may have individual placentas and amniotic sacs, but most share a placenta with separate sacs. Rarely, identical twins share one placenta and a single amniotic sac.
Women who face a multiple pregnancy may need extra monitoring from North Shore-LIJ Health System high-risk obstetrics specialists. This high-risk fellowship-trained team works closely with obstetricians to ensure that each woman receives personal service to provide the healthiest outcome for herself and her baby.
While the use of fertility methods has gained momentum, North Shore-LIJ Health System obstetricians have improved in-vitro fertilization techniques to such a degree that they are better able to control the number of embryos implanted, and reduce the chances of multiples greater than twins or triplets.
There are many factors related to having a multiple pregnancy. Naturally occurring factors include the following:
- Heredity – A family history of multiple pregnancy increases the chances of having twins.
- Older Age – Women over 30 have a greater chance of multiple conception. Many women today are delaying childbearing until later in life, and may have twins as a result.
- High Parity – Having one or more previous pregnancies, especially a multiple pregnancy, increases the chances of having multiples.
- Race – African-American women are more likely to have twins than any other race. Asian and Native Americans have the lowest twinning rates. Caucasian women, especially those over age 35, have the highest rate of higher-order multiple births (triplets or more).
Other factors that have greatly increased the multiple birth rate in recent years include reproductive technologies, including the following:
- Ovulation – Stimulating medications such as clomiphene citrate and follicle stimulating hormone (FSH) help produce many eggs, which, if fertilized, can result in multiple babies.
- Assisted Reproductive Technologies – In vitro fertilization (IVF) and other techniques may help couples conceive. These technologies often use ovulation-stimulating medications to produce multiple eggs which are then fertilized and returned to the uterus to develop.
The following are the most common symptoms of multiple pregnancy. However, each woman may experience symptoms differently. Symptoms of multiple pregnancy may include:
- uterus is larger than expected for the dates in pregnancy
- increased morning sickness
- increased appetite
- excessive weight gain, especially in early pregnancy
- fetal movements felt in different parts of abdomen at same time.
Many women suspect they are pregnant with more than one baby, especially if they have been pregnant before. Diagnosis of multiple fetuses may be made early in pregnancy, especially if reproductive technologies have been used. In addition to a complete medical history and physical examination, diagnosis may be made by:
- Pregnancy Blood Testing – Levels of human chorionic gonadotrophin (hCG) may be quite high with multiple pregnancy.
- Alpha-fetoprotein – Levels of a protein released by the fetal liver and found in the mother's blood may be high when more than one fetus is making the protein.
- Ultrasound – A diagnostic imaging technique which uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs. Ultrasounds are used to view internal organs as they function, and to assess blood flow through various vessels - with a vaginal transducer, especially in early pregnancy, or with an abdominal transducer in later pregnancy.