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all About Twin Pregnancy and Birth

In general, HCG levels are higher for twin gestation, though definitely not doubled as one might expect. In addition, many singleton pregnancies have high levels for many other reasons. Therefore, there is no set rule about checking for twins based on HCG, but there really doesn't need to be, since these patients are being scanned for whatever their underlying concern is anyway.

Vaginal bleeding is very common in any pregnancy. Simply spotting is usually a benign finding, especially in a pregnancy where ultrasound has documented the presence of fetal cardiac activity. Heavier bleeding can be a more ominous finding that should be investigated. This is true for singleton and twin pregnancies alike.

Twin pregnancies can be diagnosed as early as 4-6 weeks after a missed period. By 6-8 weeks from the missed period, two heartbeats should be seen. Usually, early ultrasounds are very likely to detect twins. At 6-12 weeks it is pretty difficult to miss a twin. Maternal anatomy can make a twin pregnancy more likely to be missed (such as a severely obese woman or one with an abnormal fibroid uterus). Higher order multiples (triplets and more) can more often be missed. No, another fetus should not develop after a singleton is seen, since they must be the same gestational age. If there are two sacs and one is empty completely and the other has a normal-appearing more advanced fetus, then no, the other will not develop.

There are many complications of pregnancy that are unique to twins, and other complications that are much more common with twins. Conditions unique to twin pregnancies include twin to twin transfusion (TTTS), which is a fairly common and potentially devastating complication of pregnancy. Premature labor, premature rupture of membranes, diabetes, and blood pressure disorders are far more likely in twin gestations than singletons. For this reason it is recommended that women pregnant with twins seek care with a provider well-trained in managing twin gestations, if not a Perinatologist or high-risk pregnancy specialist.

Conceptions resulting in twin embryos are much more common than ongoing pregnancies with twins. In as many as 30% of twin pregnancies, the second twin simply fails to develop or demises very early. Often this is seen as the concurrent presence of an "empty sac" where the second twin had implanted and had begun development. If the demise occurs very early, in the first 8-10 weeks of pregnancy, then this does not increase the rate of complications for the ongoing singleton. However, late demises in the second and third trimester can have repercussions on the surviving twin.

Read more about Vanishing Twin Syndrome

Often, the first indication of a twin pregnancy is simply an abnormal AFP, triple screen or quad screen (different variations of the same test), especially when an ultrasound has not been performed to date the pregnancy or look for twins. Again, marker levels vary even in singleton pregnancies, and levels don't simply double. for this reason the AFP is much less accurate with twin gestations (less able to screen for down syndrome). In fact, many practices do not routinely check the AFP in a multiple gestation because of accuracy concerns. For this reason, I always offer women with twin pregnancies who begin care early a Nuchal Translucency Screen which is a much better screening test for chromosome disorders in a multiple pregnancy.

If you are pregnant with twins, there are a few major things that should be done differently. Once twins are established, a specialized ultrasound to establish the "chorionicity" of the pregnancy should be done very early in the pregnancy. This is an evaluation of the membranes and placentas to see if the fetuses are sharing these entities. After that, at about 18 weeks, a specialized ultrasound should be done to evaluate growth and anatomy by someone specialized in higher risk pregnancy. I also advocate following the cervix with ultrasound, especially if it looks concerning on abdominal imaging or if a woman has a history of early delivery in prior pregnancy. In addition, growth should be followed and ultrasounds performed at least every 4 weeks. I also recommend a lower threshold for admission should there be any concern for preterm labor or a short cervix.

It is possible, but becoming much less likely. The reason is increasing concerns with the safety of vaginal breech delivery. Vaginal birth requires the first fetus to be cephalic or "head-down". If the first baby is anything but this position, vaginal delivery is unlikely and even unsafe. Once this baby is delivered, then many things can happen that could endanger the remaining twin. For instance, now that the baby is out of the way, and the cervix is wide open, the cord can come down instead of the other baby. This is very dangerous for the fetus. Sometimes as the uterus rapidly shrinks with the delivery of one baby the placenta can separate, and this also is very dangerous. Often the fetus just doesn't come down in the right position and cannot delivery vaginally. All-in-all the risk is needed to have a Cesarean section (and usually a more urgent Cesarean section) for the second twin, after a vaginal delivery of the first twin. This rate is typically quoted at being between 5% and 10% of all women with twins who attempt to delivery vaginally. Because of the potential need for quick surgery, regional anesthesia is highly recommended when delivering twins. Otherwise, should something unexpected happen the mother would have to be exposed to general anesthesia, and the delivery process would be dramatically slowed down.

Great question! Studies on twin do NOT show increased rates of rupture with a C-section scar, possibly because many deliver earlier in the pregnancy and so many women have a Cesarean section without labor anyway. In any patient, the Cesarean section rate for twins is MUCH higher than for singletons, secondary to increased rates of need for induction and abnormal presentation. Any woman undergoing a VBAC (vaginal birth after c-section) needs to understand the rate of uterine rupture and its profound consequences on mom and baby. I will VBAC twins if they had nonrecurrent reasons for their initial Cesarean section (breech, fetal anomaly), but babies have to both be head down and mom has to go into labor naturally. Many doctors would not VBAC a twin at all (some do not even VBAC a singleton for increased rates of complications). But, there is no ACOG (American College of Obstetricians and Gynecologists) recommendation that it is absolutely contraindicated in a proper patient.

Not at all, though for many I am sure it feels that way. As I stated above, the mean gestational age for delivery of twins is 36 weeks. This means half of moms will delivery after 36 weeks, or nearly at term. If you are not having issues with a short cervix, preterm labor, premature rupture of membranes, bleeding or blood pressure issues, than I highly recommend you DON'T go on bedrest. I have cared for many moms with twins that have lived life fairly normally throughout their pregnancy.

Twins usually follow normal growth curves (based on singletons) until 28-32 weeks, then they often demonstrate more sluggish growth. We usually consider a weight discrepancy of 20% or less to be normal between babies. This isn't a golden cut-off, some twins with less of a discrepancy can have a serious problem and likewise some babies with more of a discrepancy will be normal. However, it is a general cut-off that makes us our antennae go up to a potential problem.