• Nathan Riley, MD

Obgyno Wino Podcast Episode 72 - Multifetal Gestations

“Death is our friend precisely because it brings us into absolute and passionate

presence with all that is here, that is natural, that is love… Life always says Yes and

No simultaneously. Death (I implore you to believe) is the true Yea-sayer.

It stands before eternity and says only: Yes.” ― Rainer Maria Rilke

2017 Red Blend from King Estate Winery

PB #169, Published October 2016 (Reaffirmed 2016)

Five Pearls

1. Multifetal gestations have overall increased risk of morbidity for both mom and baby.

2. Chorionicity is an important piece of information for managing these pregnancies. Monochorionic pregnancies carry higher risks than dichorionic pregnancies.

3. Outside of dx of cervical insufficiency: available data doesn't support cervical cerclages, bed rest, tocolytics, or pessaries decrease morbidity or mortality associated with preterm birth in setting of multifetal gestation.

4. NIH recommends administration of corticosteroids for any pregnancy, irrespective of GA, at risk of birthing from 24-34 wga within 7 days

5. Unless monoamniotic, twin pregnancy is not a preclusion to vaginal birth

Multifetal gestations usually birth early and come with fancy risks

- 5x risk of stillbirth

- 6x risk of prematurity

- 13x risk of birth at <32 wga

- 7x risk of neonatal death due to tendency for prematurity

- increased risk for cerebral palsy (CP)

- twins born at <32 wga have 2x risk of high-grade intraventricular hemorrhage and periventricular leukomalacia than singletons of similar gestational age

- 10x greater care for preterm infants compared with term infants

Chorionicity is an independent risk factor for some bad stuff

- US is pretty reliable for diagnosing number of gestations, chorionicity, amnionicity, and estimation of gestational age

- amnion: refers to the sac

- chorion: refers to the placenta

- if there are clearly two different placenta or different fetal sexes, then you are definitely looking at a dichorionic pregnancy

Source: EasyHumanatomy on Youtube

- if it appears that only one placenta is present, look for the twin peak sign

- outcomes and risks for multi-fetal gestations differ depending on chorionicity

- dizygotic twinning is basically like two separate babies growing completely separately at the same time (two distinct sets of genetic material); always dichorionic, diamniotic (Di/Di)

- monozygotic twinning: chorionicity and amnionicity depends on timing of blastocyst division

- earlier division leads to Di/Di monozygotic twins; later division leads to Mo/Mo


- chorionicity has clinical importance: higher fetal and neonatal mortality with monochorionic versus dichorionic twins, along with risks for fetal growth restriction, congenital anomalies, and prematurity

- risks increase with higher-order gestation

- easier to diagnose by US earlier in pregnancy

Maternal morbidity and mortality is also impacted with multifetal gestations

- higher risk for hyperemasis gravidarum, GDM, anemia, postpartum hemorrhage, c-section and postpartum depression (same management as singletons)

- hypertensive complication risk in singletons: 6.5% (twins = 12%; triplets= 20%)

- relative risk (RR) of preeclampsia with twins is 2.6 (and it tends to occur earlier in pregnancy)

- multifetal gestations also more likely to present with aytpical symptoms of preeclampsia (e.g. HELLP syndrome)

- RR of preeclampsia is also increased among pregnancies conceived through assisted reproductive technology (ART) even after controlling for maternal age and parity

- all of this contributes to the higher prematurity rate (due to recommendation for preterm delivery) and higher risk for placental abruption

- risk of spontaneous multifetal gestation increases with maternal age (independent of ART use); rate is 16 per 1000 is <20 years old, 7 per 1000 if ≥ 40

Note: remember that advanced maternal age is an independent risk factor itself for complications in child combined with multifetal gestation, you need to pay attention their health throughout pregnancy...

Selective termination

- if multifetal gestation is diagnosed, the associated risks (e.g. prematurity, preeclampsia) can be decreased by selectively terminating one or more embryos/fetuses

- how does one choose? generally decision is based on accessibility to the fetus

- one of a set of monochorionic twins, if terminated, may cause issues for the surviving twin (unknown risk or consequence!)

- risk of losing a health fetus when selectively reducing a higher order pregnancy is 11% (compared to 2.5% if reducing a twin pregnancy to singleton)

Spontaneous preterm birth in multifetal gestation can't be predicted or prevented

- cervical length and fetal fibronectin aren't helpful with or without symptoms of labor

- outside of dx of cervical insufficiency: available data doesn't support cervical cerclages, bed rest, tocolytics, or pessaries decrease morbidity or mortality associated with preterm birth in setting of multifetal gestation

- 17-OHP isn't helpful, either, even with US evidence of short cervical length of <25 mm (vaginal nor IM)

Management of preterm labor in multifetal pregnancy

- tocolytics can modestly lengthen time to birth

- goal of tocolytics is to get corticosteroids on board

- first-line tocolysis method for short-term pregnancy prolongation is Ca-channel blocker (e.g. nifedipine) or NSAID (e.g. indomethacin)

- corticosteroids administered for gestations at risk of birth from 24-34 wga have been shown to reduce risk of neonatal death, RDS, NEC, and intraventricular hemorrhage (data from singleton pregnancies)

- NIH recommends administration of corticosteroids for any pregnancy, irrespective of GA, at risk of birthing from 24-34 wga within 7 days (updated practice bulletin states that this can be extended to 23 wga based - no data to support this)

- 2nd course (even in multifetal pregnancies) can be considered if 1st course was administered >2 weeks prior to 2nd course

- more than 2 courses is never recommended

- magnesium sulfate: recommended for fetal neuroprotection if preterm labor ensues <32 wga

Any difference in prenatal genetic screening for multifetal gestations?

- screening and diagnostics should be offered to any woman at any age for any order of gestation

- risk of aneuploidy is overall increased in multifetal pregnancy compared with singleton even if controlling for maternal age

- serum screening is less sensitive (false positive rate ~10%)

- nuchal translucent screening is unaffected

- limited data on NIPT as a screening method in multifetal gestation, but early results are promising

Fun fact: in a study of monochorionic twin pregnancies, a nuchal translucency value >95%tile had 38% positive predictive value for later development of severe twin-twin transfusion syndrome (TTTS)

- CVS and amniocentesis carry 1-2% risk of fetal loss, which is slightly higher than singleton

- 1% risk of sampling the wrong fetus with CVS (lower risk with amniocentesis)

Growth discordance

- defined as >20% difference in EFW

- calculated by divided their difference in weight by the weight of the larger fetus

- if at least one fetus is growth restricted (<10%tile), ~7-8x risk of major neonatal morbidity

What if one fetus spontaneously dies in-utero?

- early in pregnancy, this is known as "vanishing twin" syndrome

- 36% risk in twins, 53% in triplets, 65% in quadruplets

- Mo/Di has increased risk compared with Di/Di (twins)

- 15% chance that the 2nd twin will also die in monochorionic twins; 3% in dichorionic

- despite this data, if <34 wga, immediate delivery of the 2nd twin after demise of the 1st hasn't been shown to improve outcomes

Role of antepartum fetal surveillance

Dichorionic twins

- routine 2nd trimester anatomic surveys...obviously

- serial growth ultrasound q4-6 weeks can begin after 28-32 wga (rate of growth restriction in uncomplicated twin pregnancies is the same as singleton prior to this) in the absence of other complications

- in the absence of fetal growth restriction or other pregnancy complications, other antepartum fetal testing is only recommended for other obstetric indications

Monochorionic twins

- definitely require closer monitoring than dichorionic

- TTTS affects 10-15% of monochorionic pregnancies

- caused by an imbalance in fetal-placental circulations

- q2 week US surveillance for TTTS begins as early as 16 wga

- Quintero staging is used for classification by severity

Monoamniotic twins

- theoretical risk of "cord entanglement"

- no agreed upon management strategy When should twins ideally be birthed?

- for starters: loaded question

- twins usually spontaneously birth around 36 wga

- risk of perinatal mortality begins to rise around 38 wga (still low absolute risk)

- so the official guideline for timing of "delivery" are:

  • uncomplicated Di/Di twins: 38 wga

  • uncomplicated Mo/Di twins: 34- 37w6d

  • uncomplicated Mo/Mo twins: 32-34 wga

- if comorbidities are present or in higher-order gestations, earlier may be recommended given clinical circumstances

- unless monoamniotic, twin pregnancy is not a preclusion to vaginal birth (concern for cord complication)

- esp for uncomplicated Di/Di twin pregnancies in which presenting fetus is vertex, vaginal delivery should be considered

- if non-presenting twin is not vertex while presenting twin is birthing, non-presenting twin can be birthed by breech extraction if it doesn't vert itself while descending prior to engagement

- internal podalic version is also an option (...but why?!)

- if the 2nd twin begins to rump, let's just hope that you've been to a recent vaginal breech workshop like those offered by Breech Without Borders or Birthing Instincts

- you should also check out my podcast interview with Rixa Freeze and David Hays on vaginal breech birth

Note: If the birth attendant is comfortable with vaginal breech delivery and shared decision making has been properly engaged, then vaginal breech birth of the 2nd twin is reasonable to offer.

- higher order gestations are most likely going to end up with c-section if in a hospital because the ability to monitor more than two fetuses intrapartum is nearly impossible even with continuous fetal monitoring (shared decision making is your best friend)

Is history of prior c-section a contraindication to TOLAC in twin pregnancy?

- Hell to the no

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