Multiples' pregnancies have a shorter gestation time than singleton pregnancies, simply because mom hasn't enough room and resources to house the brood for forty weeks. On average, twin pregnancies are usually delivered at week 38, triplets at week 35, and quadruplets at week 34. The biggest risk by far in a multiples' pregnancy is preterm labor and premature birth. Gestational diabetes and preeclampsia are also risks.

Problems Mom May Face

If your body is nourishing two or more children, you need to treat it with a little extra TLC. Take an additional 600 calories daily of healthy foods (beyond average prepregnancy calorie intake), and drink plenty of water. The latter is particularly important since dehydration can trigger preterm contractions.

Moms-to-be of multiples are at greater risk for developing anemia and should speak to their provider about iron supplementation to ensure that their needs are covered. Increasing your intake of iron-rich foods is a good way to ward off anemia. Try rotating iron-fortified foods such as baked beans, blackstrap molasses, wheat germ, raisins, beef, and leafy green veggies (like spinach, kale, and broccoli) into your diet. (For more on eating right in pregnancy, review Chapter 7.)

The cervix has heavy work to do in a multiples' pregnancy. Having twins puts you at increased risk of preterm labor. Some physicians have recommended serial screening of the cervical length using transvaginal ultrasound to try to detect early cases of preterm labor. A screening of the cervical length at around week 20 appears to be predictive of who will deliver preterm. In women with a short cervix (approximately 25 mm or less at week 24), some reinforcements may be required. If cervical shortening is suspected, a transvaginal ultrasound, in which the Doppler wand is inserted into the vagina rather than moved across the belly, is used to assess cervical length and monitor the progress of the cervix. Cerclage, a procedure involving suturing (or stitching) the cervix closed to avoid preterm dilation, is not routinely indicated for multiples' pregnancy but is sometimes performed for preterm cervical shortening and dilation.

Although due dates are typically based on a ten lunar-month calendar, most people consider pregnancy a nine-month, three-trimester affair. That's why you'll find your pregnancy divided into nine calendar months in this book. (For more on estimating your due date, see Chapter 2.)

Studies are inconclusive as to whether or not rescue cervical cerclage is effective in improving birth outcomes, but it does appear that the earlier cerclage (that is, not rescue) is performed in the pregnancy, the more potential it has for success. Cerclage is usually performed in the second trimester.

Almost half of all multiples' pregnancies result in preterm labor (labor before week 37). If you start having contractions or other signs of preterm labor, your provider might try to halt labor until you're further along in your pregnancy by one or more of the following methods:

Bed rest: Strict bed rest may be imposed to keep the pressure off your cervix. This could be at home (with a few bathroom passes granted) or in a hospital. A fetal monitor may be used to keep an eye on the team's progress.

Fluids: You may be hooked up to an intravenous line and/or fed fluids to keep you hydrated.

Trendelenburg position: Bed rest — to the extreme. If your provider mentions this, he wants you on a bed that works against gravity by elevating your feet and tilting your head down.

Tocolytic medication: Tocolytic drugs like magnesium sulfate, calcium channel blockers, and terbutaline may be administered by mouth or intravenously to stop contractions. Indocin has also been used with some success.

Antibiotics: If your membranes have ruptured prematurely (preterm premature rupture of membranes, or PPROM), antibiotics can help to ward off infection and prolong the latent phase of labor. They are also used to prevent group B strep infection in the preterm newborn.

An amniocentesis can determine whether the fetal lungs are developed enough to breathe in the outside world (see Chapter 5 for more on amniocentesis). If results indicate that the lungs are still immature, injections of corticosteroids may be administered to accelerate surfactant production while labor is held off as long as possible. The ACOG recommends steroid treatment for women expected to deliver at week 34 or earlier in pregnancy.

There are some situations in which tocolysis should not be attempted, even if you are considerably preterm. If monitoring indicates that your fetus is in distress, if you have signs of infection of the amniotic fluid, or if you are bleeding excessively, tocolyctic drugs are not recommended. In most of these cases, immediate delivery is required.

In amniocentesis of multiples, a blue dye is injected into each amniotic sac after a fluid sample is withdrawn. If the same sac is accidentally tested twice, the appearance of the dye will tip off the physician to the error. It's important that all sacs be tested whenever practical, since multiples often develop at different rates and may have achieved various levels of fetal lung maturity.

Problems Babies May Face

Up to 70 percent of monoamniotic twins and higher-order multiples experience umbilical cord knotting, twisting, or entanglement. In severe cases, kinks or tangles in the cord can cut off blood supply to one or both fetuses. Ultrasound can determine the presence or absence of a dividing membrane between multiples. If a multiples' monoamniotic pregnancy is detected, it will be followed closely with routine ultrasounds to check for umbilical cord complications. Regular nonstress testing (NST) may also be employed to evaluate fetal health. (For more on diagnostic tests, review Chapter 5.)

The length of expected gestation decreases with each additional fetus carried in a pregnancy. According to the March of Dimes, nearly 60 percent of twins, over 90 percent of triplets, and virtually all quadruplets and higher multiples are born preterm (before week 37 of gestation).

Twin-to-twin transfusion syndrome (TTTS) is a rare condition affecting approximately 10 percent of those identical twins who share a chorionic membrane and placenta. In TTTS an abnormality in the placenta causes irregularities in fetal blood circulation, and blood is shunted between the fetuses through placental vessels that connect them. The result is that one fetus experiences cardiovascular overload and potential heart failure, while the other receives insufficient blood flow. TTTS is not limited to twins and can occur in higher-order multiples' pregnancies as well.

In addition to its involvement with TTTS, the position and construction of the placenta can impact the growth of one or more multiples. Maternal blood flow and nutrition may be unequally distributed among fetuses, resulting in an uneven growth rate among them. Multiples can also be at a higher risk for intrauterine growth retardation (IUGR). (For more on that condition, see Appendix A.)

Vanishing twin syndrome entails the death of one twin that was previously viable. When it occurs early in pregnancy, the body is typically reabsorbed into the uterine wall. Some minor bleeding and cramping may signal the process. More serious complications can result if vanishing twin syndrome happens later in pregnancy, including cerebral palsy in the surviving twin and potential circulatory problems in the mother.

Other conditions multiples are considered at high risk for include congenital abnormalities and placental problems (for example, placenta previa, placental abruption). (For more on these conditions, see Appendix A.)

A laser-surgical technique developed in the 1980s can be used to successfully treat some cases of TTTS. Fetoscopic laser occlusion of the connecting placental blood vessels (FLOC) uses an endoscope (a thin, flexible tube with a tiny camera attached) to find the blood vessels connecting multiples and close them off.