Impact of past obstetric history and cervical excision on preterm birth rate

IntroductionTo determine the impact on preterm birth (PTB) of a history of large loop excision of the transformation zone (LLETZ)-alone compared with a history of previous preterm birth-alone (PPTB) or a history of both (LLETZ+PPTB). Secondary analyses were performed to evaluate the impact of antenatal interventions, depth of cervical excision, and patient risk factors on PTB rate in each cohort.Material and methodsA retrospective observational cohort study of women referred to a tertiary Antenatal Prematurity Prevention Clinic with a history of LLETZ, PPTB, or LLETZ+PPTB. Information was collated from routinely collected clinical data on patient demographics, previous obstetric history, LLETZ dimensions, antenatal investigations/interventions, and gestation at delivery.ResultsA total of 1231 women with singleton pregnancies were included, 543 with history of LLETZ-alone, 607 with a history of PPTB-alone and 81 with a history of LLETZ+PPTB. PTB rates were 8.8% in the LLETZ-alone group, which mirrored the PTB rate in the local background obstetric population (8.9%) compared with 28.7% in the PPTB-alone and 37.0% in the LLETZ+PPTB cohorts. PTB rates were higher in LLETZ cohorts treated with antenatal intervention (cervical cerclage or progesterone pessary) and there was no evidence of an effect of intervention on risk of PTB in post-excision patients with identified shortened mid-trimester cervical length. Logistic regression modeling identified PPTB as a strong predictor of recurrent PTB. Excision depth was correlated with gestation at delivery in the LLETZ-alone group (r = −0.183, p ConclusionsPPTB has a greater impact on subsequent PTB risk compared with depth of cervical excisional treatment. The value and nature of antenatal interventions should be investigated in the post-excision population.</div

Description of <i>NLRP7</i> mutations with methylation and expression profiling of imprinted loci.

<p>(A) Confirmation of recessive <i>NLRP7</i> mutations in female patients and heterozygous status in the RHM samples. The asterisk (*) on the electropherogram highlights the position of the mutation. For patient 3 the position of the deletion is shown. (B) Circular heat map of the 616 Infinium array probes mapping to 36 ubiquitously imprinted DMRs. The inner circle represents the methylation values of androgenetic HMs, the middle circles normal placental biopsies and the outer circle the RHMs associated with maternal-effect <i>NLRP7</i> mutations. (C) Confirmation of the methylation profile of the <i>NLRP7</i> mutated RHMs at the <i>NAP1L5</i>, <i>PEG10</i>, <i>RB1</i>, <i>L3MBTL1</i> and <i>H19</i> DMRs by bisulphite PCR and subcloning. Each circle represents a single CpG dinucleotide on a DNA strand, a methylated cytosine (●) or an unmethylated cytosine (○). For clarity, only the first 10 CpG dinucleotides from each amplicon are shown with the letters in the parentheses indicating SNP genotype. (D) Allelic expression analysis of imprinted genes <i>NAP1L5</i>, <i>HYMAI</i>, <i>PEG10</i> and <i>PEG3</i> in control placenta samples (PL) and <i>NLRP7</i>-mutated moles (RHM).</p

Identification of additional placenta-specific imprinted DMRs in RHM samples.

<p>(A) A heatmap for the β_mean of the Infinium probes with a methylation difference (>20%, minimum 3 consecutive probes) in RHMs associated with maternal effect <i>NLRP7</i> mutations compared to control placental biopsies. (B) Schematic representation of the methylation-sensitive <i>Hpa</i>II genotyping assay. (C) Methylation profiles as determined by methylation-sensitive genotyping and (D) bisulfite PCR and subcloning on placenta and somatic tissue DNA samples at the <i>SCIN</i>, <i>ST8AIA1</i> and <i>CABIN1</i> promoters. Note that the samples used for methylation-sensitive genotyping and bisulphite PCR maybe different to highlight that methylation is not associated with genotype but parental origin.</p

Methylation and expression analyses of placenta-specific DMRs in RHM samples.

<p>(A) Circular heatmap of the 153 Infinium array probes mapping to the 18 known placenta-specific imprinted DMRs. The inner circles represent the methylation values of androgenetic HMs, the middle circles normal placental biopsies and the outer circle the RHMs associated with maternal-effect <i>NLRP7</i> mutations. (B) Confirmation of the methylation profile at the maternally methylated <i>GLIS3</i>, <i>DNMT1</i> and <i>MCCC1</i> DMRs by bisulphite PCR and subcloning. Each circle represents a single CpG dinucleotide on a DNA strand, a methylated cytosine (●) or an unmethylated cytosine (○). For clarity, only the first 10 CpG dinucleotides from each amplicon are shown with the letters in the parentheses indicating SNP genotype. (C) Allelic expression analysis of imprinted genes <i>MCCC1</i>, <i>LIN28B</i> and <i>GLIS3</i> in control placenta samples (PL) and <i>NLRP7</i>-mutated moles (RHM). (D) Quantitative RT-PCR for <i>H19</i>, <i>DNMT1</i> and <i>AGBL3</i> in RHM samples. The boxplot show the median expression (whiskers 5–95% percentile) determined for 15 control placenta samples with the values of RHMs highlighted.</p