Placental pathology and risk of recurrent preterm birth

Abstract

Preterm birth (PTB) is the leading cause of perinatal mortality and morbidity. Although our understanding of the etiology behind this pregnancy complication is poor, it has a tendency to recur.1Ananth C.V. Getahun D. Peltier M.R. Salihu H.M. Vintzileos A.M. Recurrence of spontaneous versus medically indicated preterm birth.Am J Obstet Gynecol. 2006; 195: 643-650Abstract Full Text Full Text PDF PubMed Scopus (162) Google Scholar,2Yang J. Baer R.J. Berghella V. et al.Recurrence of preterm birth and early term birth.Obstet Gynecol. 2016; 128: 364-372Crossref PubMed Scopus (63) Google Scholar Patients who have had a previous PTB are usually very anxious during the second pregnancy, which itself can lead to spontaneous PTB. Therefore, risk predictors individual to a patient’s pregnancy or delivery are needed to aid counseling for these patients. Recently, Suresh et al3Suresh S.C. Freedman A.A. Hirsch E. Ernst L.M. A comprehensive analysis of the association between placental pathology and recurrent preterm birth.Am J Obstet Gynecol. 2022; ([Epub ahead of print])Abstract Full Text Full Text PDF Google Scholar determined the independent contributions of the major placental pathology histologic types toward recurrent PTBs in a total of 924 pregnancy pairs. The authors reported that only high-grade chronic inflammation was independently associated with an increased risk of recurrent PTB. They concluded that placental pathology can be utilized to change risk assessment. However, the study raises some important issues that should be addressed. The placenta was submitted for pathologic review in 947 (57.2%) index PTBs and not submitted in 708 (42.8%). Subsequent pregnancy outcome (gestational age) was available in 924 (97.6%) out of 947 cases with placental pathology, including 376 early PTBs (<34 weeks) and 548 late PTBs (34–36 weeks). The authors mentioned that standardized institutional indications for the examination of placentas by pathology included the following: intrauterine fetal demise, fetal growth restriction, PTB ≤34 weeks’ gestation, severe preeclampsia, etc. This indicated that most of the 548 cases of late PTB had other adverse conditions. In other words, obstetricians would not apply for a pathologic examination in the case of late PTB without a coexisting undesirable condition. Therefore, it would be interesting to know the recurrent rate in the 708 patients with index PTBs but no placental histology. The risk of recurrent PTB was 27% in the study sample. Were there any differences between patients with early PTB and those with late PTB? Was the pathologic type of placenta correlated with a maternal medical condition? Indeed, one finding of this study confirmed the results of a previous study that recurrent PTB was more likely to occur among women with inflammatory lesions observed on placental pathology from a previous PTB.4Himes K.P. Simhan H.N. Risk of recurrent preterm birth and placental pathology.Obstet Gynecol. 2008; 112: 121-126Crossref PubMed Scopus (35) Google Scholar Chronic inflammation has been implicated, particularly in late PTB. Another finding was that low-grade maternal vascular malperfusion was associated with recurrent PTB only among those with early PTB (<34 weeks). The authors did not discuss the implications of this finding. We speculate that the risk factors of early PTBs are different from those causing late PTBs. Therefore, they could not be evidenced by placental pathology. Response to: placental pathology and recurrent preterm birthAmerican Journal of Obstetrics & GynecologyVol. 227Issue 6PreviewWe thank Chen et al1 for their interest in our work.2 The indications for placental examination as stated are recommendations and not fully reflective of clinical practice. Although preterm birth (PTB) at >34 weeks was not a “standard” indication for placental examination, in our cohort, 52.9% of preterm placentas >34 weeks were sent to pathology, at a rate similar to the rate of 64.2% of placentas of those who delivered at ≤34 weeks sent to pathology. The risk of recurrent PTB in our >34 week samples was similar among the included (pathology) and excluded (nonpathology) samples (21.8% vs 22.2%). Full-Text PDF