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Multifetal Pregnancy Reduction
Introduction
Multiple gestations are at risk for perinatal morbidity and mortality that increase with higher-order pregnancies, primarily caused by complications of prematurity. The risk of preterm delivery increases as the number of fetuses increases. In 2014, preterm delivery <32 weeks occurred in 1% of singletons, 11% of twins, 39% of triplets, and 72% of quadruplets. Infant mortality increases fourfold in twins, 12-fold in triplets, and 26-fold in quadruplet births.
In addition to perinatal concerns, maternal risk is also significantly increased in higher-order pregnancies. Compared with twins, triplet pregnancies were at higher risk for pregnancy-associated hypertension (odds ratio [OR], 1.22; 95% confidence interval [CI], 1.15–1.30), eclampsia (OR, 1.69; 95% CI, 1.46–19.4), cesarean delivery (OR, 6.55; 95% CI, 6.15–6.97), and excessive bleeding in labor and delivery (OR, 1.41; 95% CI, 1.25–1.56).
The incidence of multifetal pregnancies has increased significantly over the past 3 decades, primarily because of the success of assisted reproductive technologies. The twin birth rate increased by 76% from 1980 to 2009, and accounted for 3.39% of live births in 2014. Triplet or higher-order pregnancies increased by 400% between 1980 and 1998. However, the rate of higher-order pregnancies had declined by 40% by 2009 as a result of primary prevention such as guidelines advocating the transfer of fewer embryos and secondary prevention with multifetal pregnancy reduction (MFPR).
In the 1980s several authors reported on MFPR as a method to improve maternal and fetal outcomes in high-order multiple pregnancies. This procedure involves the termination of one or more presumably normal fetuses to increase the overall likelihood of survival, and to decrease the long-term morbidity of the remaining fetus or fetuses. MFPR increases the rate of live birth, while decreasing the risk of pregnancy loss, preterm delivery, neonatal/infant demise, preeclampsia, and gestational diabetes.
Procedure
Setting
MFPR is performed as an outpatient procedure in an ultrasound (US) unit in the late first or early second trimester.
Counseling
The American College of Obstetrics and Gynecology recommends nondirective counseling when reviewing the details of a patient's multifetal pregnancy (maternal health issues/risks, number of fetuses, and potential outcomes of pregnancy continuation versus reduction). The psychologic, economic, social, and health risks should be addressed before the procedure. The risks of the procedure should be reviewed, as well as the expected prognosis.
US should be performed before counseling to determine fetal number, chorionicity, and screen for possible genetic, growth, or anatomic abnormalities. The chorionicity of the pregnancy should be identified as early as possible, as this will affect the counseling relating to fetal selection for termination. Monochorionic twins are fraught with potential concerns, such as twin-twin transfusion syndrome and unequal placental sharing. Potassium chloride (KCl) termination of one fetus is contraindicated in a monochorionic twin gestation, as the anastomoses in the shared placenta may cause an inadvertent termination of the co-twin. Radiofrequency cord ablation can be used to selectively terminate one fetus in monochorionic twins, but this is associated with a higher risk of preterm labor, delivery in the periviable period, and loss of the pregnancy. Consideration should be given to reducing both monochorionic twins when present in a higher-order multiple pregnancy.
Risks of the procedure are similar to the risks of amniocentesis, including amniotic fluid leakage from the sac of a viable fetus, placental abruption, infection (chorioamnionitis), and pregnancy loss.
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