Pregnancy Twins and Multiples
Reviewed by Dr. Edward Kulich
The term multiple births simply means more than one fetus during a single pregnancy. This can be caused by race, heredity, number of previous pregnancies, delayed childbirth, and/or infertility treatments. Older women are always more susceptible to conceive multiples, even if they have not used infertility treatments. However, all women are capable of conceiving multiples. Multiple births involve risks and complications that can affect both the babies and mother, and should be closely monitored by an obstetrician with experience in managing pregnancies with multiples. Women who have had other babies, have recently discontinued birth control, or have a higher body mass index (BMI) are more likely to have a multiple pregnancy.
Identical vs. Fraternal
Monozygotic (identical) and Dizygotic (fraternal) pregnancies occur most commonly as a result of infertility treatments. Identical fetuses come from a single egg and are genetically identical (features, gender, and DNA). Only 3-4 out of every 1,000 pregnancies are identical twins, and things like race, heredity, and age DO NOT influence this random event. Fraternal fetuses occur when multiple eggs are fertilized by different sperm. They can be the same gender or different and usually they don’t look alike. Even though they were carried during the same pregnancy, they are no more genetically similar than normal siblings. Some cultures are known to have a higher incidence of twinning, namely the Yoruba tribe in Brazil.
Higher Order Multiples
Higher order multiples include sets of triplets, quadruplets, quintuplets, etc. Variations of identical and fraternal multiples can and will occur. It’s not uncommon for a set of triplets to include one baby who is fraternal while the other two are identical, or vice-versa.
Signs and Symptoms
Women who think they might be pregnant with more than one fetus will experience rapid weight increases during the first trimester. During an ultrasound the doctor may notice the uterus is much larger than expected, which is a good sign of at least twins being present. Higher HCG levels and more intense or severe pregnancy symptoms like nausea, vomiting, and breast tenderness are all signals that there may be more than one fetus. These symptoms, however, may be absent with multiples and are not reliable indicators of twinning.
Pregnancies with multiples tend to last 35-37 weeks instead of the normal 40 week gestation period, which could be the cause of various complications. Doctors may increase number of appointments during the pregnancy to monitor the mother and babies. Preterm labor, PIH (pregnancy induced hypertension), fetal well-being, fetal demise loss, low birth weight, and preeclampsia are all complications mother and babies may experience before and after birth.