Mallory Hoffman, MD - 2024 Fetal Care Center Navigating Perinatal Care for Trisomy 13 & 18

13% of patients with trisomy 13 or trisomy 18 had preterm labor, not significantly different from the general population rate of about 10%.

Polyhydramnios in trisomy 13/18 can result from GI blockage, micrognathia preventing swallowing, or brain differences affecting swallowing signals.

Amnio-reduction uses a 20-gauge spinal needle and may remove several liters of amniotic fluid to relieve uterine stretch and prolong pregnancy.

The risk for stillbirth in trisomy 13/18 once in the third trimester is about 13%.

Non-stress tests are recommended twice weekly to help detect fetal distress earlier, though they are not perfect for preventing stillbirth.

Growth restriction and Doppler abnormalities may prompt earlier delivery timing.

The cesarean section rate for trisomy 13/18 pregnancies is 48%, compared to 32% in the general US population.

Increased cesarean section risk in trisomy 13/18 may be related to smaller babies, placentas that don't tolerate labor well, or structural differences like omphalocele or enlarged head size.

Patients at a fetal care center are more selected toward those interested in interventions after delivery, compared to general MFM practices.

Financial limitations and late diagnosis can restrict access to out-of-state termination, leading more patients to choose comfort care.

Some OB providers still counsel that comfort care is the only option for trisomy 13/18, reflecting outdated teaching that these are uniformly lethal diagnoses.

Medical school teaching historically presented trisomy 13/18 as lethal, with survivors assumed to be mosaic; more recent evidence shows full trisomy cases can survive beyond one year with support.

Ohio has a ban on termination for Down syndrome (trisomy 21), which has led some clinics to require amniocentesis confirmation for high-risk trisomy 13/18 screens to ensure it is not trisomy 21.

Rates of preeclampsia are higher in pregnancies with abnormal placentas, which is typical in trisomy 13/18.

Classical cesarean incisions (vertical on the uterus) do not heal as well as low transverse incisions and require preterm cesarean sections in all future pregnancies.

ACOG supports cesarean section on maternal request, meaning any mother who requests a C-section can have one even without a fetal indication.

In inductions with no fetal monitoring, the baby is often still born alive.

Families commonly change their minds multiple times during pregnancy and even during labor regarding their care preferences.

NIPT performs best for trisomy 21, then less well for trisomy 18, and least well for trisomy 13, partly due to technical factors and partly due to disease prevalence affecting positive predictive value.

NIPT tests free placental DNA, not fetal DNA, so false positives may reflect confined placental mosaicism rather than true fetal abnormality.

False positive NIPT results cause significant stress, often occurring in a diagnostic gray zone between CVS and amniocentesis timing.

Even after a low-risk amniocentesis following high-risk NIPT, growth scans in the third trimester are recommended due to potential placental impact on fetal growth.