#Grand Rounds

NICHD RTC Secondary Analysis: What is the Impact of Indicated vs Spontaneous Preterm Birth on Pregnancy Outcomes?

BACKGROUND AND PURPOSE:

Up to 75% of preterm birth is spontaneous (SPTB) while remainder are indicated (IPTB) deliveries, based on maternal or fetal complications
Public health policy may suggest focusing resources on the more common SPTB cohort, but there is limited data as to which group has the burden of adverse events
Tita et al. (American Journal of Perinatology, 2018) compared the risks of adverse maternal and neonatal outcomes associated SPTB vs IPTB

Retrospective Cohort Study
- Secondary analysis of multicenter trial including women with SPTB and IPTB
- Original study: NICHD RCT of vitamin C and E to prevent preeclampsia in low risk nulliparous patients
Primary exposure: PTB (<37w0d) – SPTB vs IPTB
Primary maternal outcome: Composite of the following
- Death |Pulmonary edema |Blood transfusion | ARDS | Cerebrovascular accident | ATN | DIC | Liver rupture
Primary neonatal outcome: Composite of the following
- Neonatal death | RDS | Grades III or IV IVH |Sepsis | NEC | ROP

9,867 women were included in the study
- 1,038 women underwent preterm births
- 340 IPTBs
- 698 SPTBs

Maternal Adverse Events

Composite maternal outcome was more frequent in IPTB (4.4%) vs SPTB (0.9%)
- adjusted odds ratio [aOR], 4.0 (95% CI, 1.4–11.8)
Blood transfusion was more common in IPTB (3.4%) vs SPTB (0.9%); P=0.005
- aOR 3.2 (95% CI, 1.1-9.8)
Prolonged hospital stay was more frequent in ITPB (8.7%) vs SPTB (1.8%); P<0.001
- aOR 3.7 (95% CI, 1.8-7.7)

Newborn Adverse Events

Composite neonatal outcome was less frequent in IPTB (22.6%) vs SPTB (24.1%) but when adjusted for confounders inlcuding demographics and peripartum infections, risk increased
- aOR, 1.8 (95% CI, 1.1–3.0)
Other outcomes that were increased in IPTB vs STB group
- RDS: aOR 1.7 (95% CI, 1.1-2.7)
- SGA <5th percentile: aOR 7.9 (95% CI, 4.0-15.7)
- NICU admission: aOR 1.8 (95% CI, 1.3-2.5)
Crude risk of death higher in SPTB
Most frequent reason for IPTB was pregnancy-associated hypertension
- Outcomes for this indication only were similar to the overall group, except that neonatal composite and RDS were no longer statistically different

IPTB vs SPTB have a fourfold higher incidence of maternal adverse events
The authors state that based on the results of this study “interventions to prevent the underlying causes of IPTBs such as preeclampsia, to reduce the risk of IPTBs and hence reduce the associated burden of adverse outcomes may deserve as much attention as directed toward SPTBs”

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