Triplet pregnancy is associated with significantly increased risks of maternal and neonatal morbidity compared with twin pregnancy. In a study that compared outcomes of 12,193 triplet pregnancies with 316,696 twin pregnancies, triplet pregnancies had significantly higher frequencies of diabetes, anemia, amniotic fluid abnormalities, pregnancy-associated hypertension, eclampsia, cervical insufficiency, uterine bleeding, use of tocolysis, cesarean delivery, abruption, and placenta previa .
The management of triplet gestations and pregnancy complications during mid to late pregnancy will be reviewed here. The incidence, diagnosis, and early prenatal care of triplet pregnancy are discussed separately. (See "Triplet pregnancy: Early pregnancy management".)
Preterm delivery is a common, serious complication of triplet gestation: 75 to 100 percent of triplets are born prematurely. The average duration of gestation for singletons, twins, and triplets is 39, 35, and 32 weeks, respectively . About 95 percent of triplets have birth weights <2500 grams (ie, low birth weight [LBW]) and 35 percent <1500 grams (ie, very low birth weight [VLBW]). By comparison, the rates of LBW and VLBW in singletons are 6.5 and 1.1 percent, respectively. A previous pregnancy resulting in the term birth of an appropriately grown neonate is predictive of longer gestation and higher birth weight in a subsequent triplet pregnancy .
The primary cause of preterm birth in triplet pregnancy is spontaneous preterm labor, with or without preterm premature rupture of membranes (PPROM). Preeclampsia and fetal growth restriction are the most common causes of indicated preterm birth. These complications are more common in multiple gestations than in singleton gestations and account for a large proportion of the excess rate of preterm birth in multiples.
Overview of monitoring and intervention — No intervention has been proven effective in reducing the incidence of spontaneous preterm birth in triplets. We perform sonographic cervical length measurement at 19 to 20 weeks of gestation to identify women at highest risk of developing preterm labor. While the optimum cervical length threshold for cervical shortening in triplet gestations has not been established, a cervical length of ≤25 mm before 25 weeks in triplet pregnancies appears to be predictive of an increased risk for birth prior to 28 to 32 weeks of gestation and is the threshold we use [4-8]. We also see our patients every other week in the office starting at 24 weeks of gestation to ask about symptoms of preterm labor and perform digital examination and/or cervical length ultrasound if they are symptomatic. In patients over 24 weeks with equivocal findings, we obtain a fetal fibronectin test. Alternatively, one can simply obtain a cervical length every two weeks or a fetal fibronectin every two weeks. The combination of both a positive fetal fibronectin result and a short cervical length on ultrasound examination is more predictive of preterm birth within seven days than either test alone [9,10]. (See "Transvaginal ultrasound assessment of the cervix and prediction of spontaneous preterm birth" and "Fetal fibronectin for prediction of preterm labor and delivery".)