Of all multiples, twins normally face the fewest medical problems and complications. Each additional baby a woman carries at one time increases the possibility of developing complications.
Preterm labor/delivery is defined as delivery before 37 completed weeks of pregnancy. The length of gestation decreases with each additional baby. On average most single pregnancies last 39 weeks, twin pregnancies 36 weeks, triplets 32 weeks, quadruplets 30 weeks, and quintuplets 29 weeks. Almost 60% of twins are delivered preterm, while 90% of triplets are preterm. Higher order pregnancies are almost always preterm. Many times premature labor is a result of preterm premature rupture of the membranes (PPROM). PPROM is ROM (rupture of membranes) prior to the onset of labor in a patient who is at less than 37 weeks of gestation.
Low birth weight is almost always related to preterm delivery. Low birth weight is less than 5½ pounds (2,500 grams). Babies born before 32 weeks and weighing less than 3 pounds (1,500 grams) have an increased risk of developing complications as newborns as well as having long-term problems such as mental retardation, cerebral palsy, vision loss, and hearing loss.
Multiple gestations grow at approximately the same rate as a single pregnancy up to a certain point. The growth rate of twin pregnancies begins to slow at 30 to 32 weeks. Triplet pregnancies begin slowing at 27 to 28 weeks, while quadruplet pregnancies begin slowing at 25 to 26 weeks. IUGR seems to occur because the placenta cannot handle any more growth and because the babies are competing for nutrients. Your doctor will monitor the growth of your babies by ultrasound and by measuring your abdomen.
Preeclampsia, Pregnancy Induced Hypertension (PIH), Toxemia, and high blood pressure are all synonymous terms. Twin pregnancies are twice as likely to be complicated by preeclampsia as single pregnancies. Half of triplet pregnancies develop preeclampsia. Frequent prenatal care increases the chance of detecting and treating preeclampsia. Adequate prenatal care also decreases the chance of a serious problem resulting from preeclampsia for both the babies and mother.
The increased risk for gestational diabetes in a multiple pregnancy appears to be a result of the two placentas increasing the resistance to insulin, increased placental size, and an elevation in placental hormones. The occurrence of gestational diabetes in a multiple pregnancy is still being tested at this time. In one study, an increased risk of gestational diabetes did seem to be apparent, but the doctors involved recommended that further testing be conducted.
Placental abruption is three times more likely to occur in a multiple pregnancy. This may be linked to the fact that there is an increased risk of developing preeclampsia. It most often occurs in the third trimester, but the risk significantly increases once the first baby has been delivered vaginally.
Intrauterine fetal demise is extremely uncommon. Your healthcare provider will determine whether it is best to expose the other baby(ies) to the fetus that has died or to proceed with delivery. If the pregnancy is dichorionic (two chorions present), then intervention may not be necessary. (The chorion is a membrane that forms the fetal portion of the placenta. Fraternal twins always have two chorions while identical twins can have one or two chorions.) If the pregnancy has a single chorion then fetal maturity will be assessed to see if immediate delivery is achievable. In this situation it would be necessary to evaluate the risks between having a premature baby to the risks of remaining in utero.