There is a certain romance to twins. Generally what is envisioned is the double stroller being pushed down the street, garnering all of the attention, the identical outfits accentuating twins' likeness, and admiration of the parents from all for surviving such a grueling infant period. There's a certain glory to twins. And all of this is fair, because twins are special. It is a double blessing. Take the most important gift you can receive, double it, and you have twins.
But twins create a high-risk pregnancy, and an obstetrician must watch this pregnancy very carefully, because a twin gestation makes more likely a most dangerous complication--premature delivery. If a woman carrying a single baby were to wonder how much more pregnant she can get at, say, eight months, imagine what it feels like when hitting that point at six months with twins. If it seems like there's no more room for baby in a single pregnancy, then twins get just plain ridiculous. The body thinks so, too, and tends to want to deliver prematurely what it thinks is just a single big mature baby months before twins are ready.
Vigilance for premature labor can involve medicines for premature labor, hospitalization, weeks of bed rest, and still....a premature delivery. Another concern is whether one twin will get more than its share of oxygen and nutrition at the expense of the other. Called discordancy, one twin will grow too big and the other not enough. Ironically, this puts both in grave danger, as the overload on the larger twin can be just as lethal as the deprivation to the smaller.
Many ultrasounds are needed in twin gestations to make sure the babies are both growing at roughly the same rate. If twins are identical, there's a chance that they might share the same sac instead of there being a dividing membrane between them; this makes cord entanglement a real possibility, putting both babies in mortal danger. Once again, ultrasound comes to the rescue to show the membrane that would put that worry to rest. All of the complications of a single pregnancy can have earlier onset in twins, since there's an obvious increase in the give-and-take in the mother-baby physiologic relationship.
Preeclampsia (toxemia), consisting of a symptom collection of high blood pressure, swelling, kidney problems, and possibility of seizures, is more likely to occur (and earlier) in a twin pregnancy. Placental accidents are more likely too. Placenta previa, wherein the placenta lies over the opening of the womb, blocking the route out for a vaginal delivery, is more likely because there's more placenta there and less space for it to occupy. Placental abruption, a premature tearing away of the placenta, is also more likely than in single pregnancies. This event could result in significant blood loss, danger of transfusion for the mother, and mortal risk for the babies.
Delivery poses dangers as well. The jumbling together of two babies makes for frequent abnormal positioning of one or both twins. Breech babies are frequent, as are impossible-to-deliver presentations like shoulder- or transverse-presentations. This "malpresentation" can make C-section the safest way to deliver. Prolapse of an umbilical cord is more frequent with such malpresentations, so therefore it is more frequent with twins. A cord prolapse can pinch the cord, cutting off oxygen to the baby.
And now the good news: modern obstetrical care and careful surveillance of two babies usually yields a good result. Even though multiple gestation is definitely high risk, we have at our disposal tools to closely monitor the pregnancy and birth and intervene when necessary. Having twins is the most dramatic argument for good prenatal care, because it's a situation where prenatal care can be so crucial for a healthy outcome.
The special gift of twins occurs in slightly more than one in a hundred pregnancies, but this number will certainly change for the bigger as more infertility drugs are used in more aggressive attempts at pregnancy. As obstetricians dedicated to the best prenatal care, we know we'll be seeing more of this than previously.
Let the romance continue, we're ready.