Genetic Studies of Spontaneous Preterm Birth in Ghanaian Women

Abstract

Background: Live birth before 37 gestation weeks, also known as preterm birth affects approximately 13.4 million births globally. Complications of preterm birth are responsible for about 1 million child deaths worldwide and lead to neonatal death every hour in Ghana. Approximately, two-thirds of preterm births occur spontaneously. However, the aetiology of spontaneous preterm birth (SPTB) is poorly understood. African women have the highest incidence of SPTB globally, even if environmental and socioeconomic conditions are adjusted for, suggesting a peculiar genetic predisposition. Genetic studies of SPTB in Africa are virtually unavailable. Understanding the genetic linkage will enhance the development of appropriate interventions. The study sought to identify specific phenotypes and genetic variants associated with SPTB among Ghanaian women. It was based on the hypothesis that SPTB among Ghanaian women is associated with a unique genetic variant. Methods: The use of human subject for this study was approved by Ghana Health Service Ethics Review Committee with additional permission from all study centres. Informed consent was documented for all study participants prior to recruitment. The participants were recruited from seven health facilities across Ghana. Participants with acute infection and/or non-communicable diseases were excluded. A case-control study design was used involving 604 post-partum mothers with singleton births. Cases were 277 mothers with SPTB and controls were 327 mothers with term birth. Gestational ages of 24 to 42 weeks were considered. The demographic and phenotypic characteristics were identified through health records and structured interview questionnaire. Maternal psychological distress was assessed using the CES-D Scale. Maternal knowledge of their personal or immediate family (sister and mother) history of preterm birth was also assessed via interviews. Neonatal anthropometries including birth weight, head circumference, length, and first and fifth minute Apgar scores were assessed. Placental samples were also collected for histological and RT-qPCR assessment. Whole blood (5 ml) was collected from each mother for DNA isolation and analysis. Six polymorphisms SERPINH1 (- 656 C/T), ADCY5 rs9861425 (A/C), AGTR2 rs5950491 (C/A), MMP-1 (-1607 1G/2G), EEFSEC rs2955117 (G/A) and WNT-4 were genotyped using restriction fragment length polymorphism (RFLP). Univariate and multivariate analysis were conducted using the open-source statistical software R. Result: Maternal age less than 20 years, less than antenatal 4 visits and depression were independently associated with SPTB by about 2-fold. Nulliparity, moderate Hb (Hb 9.9 – 7.0 g/dl) and “Not married status” were associated with increased SPTB risk by 64%, 60% and 71%, respectively but the associations were not independent. Chorioamnionitis was detected in 12.2% of placental samples. Its prevalence was high among SPTB placentas (16%) compared with 8.82% among term birth placentas. However, the difference was not statistically significant (p < 0.07). Indicators of maternal placental malperfusion were also detected in 6 out of 10 SPTB placental tissues. Ghanaian neonatal anthropometries (birth weight, head circumference and length) started dipping and diverged from that of the Olsen curve from the 29th gestation week till delivery either as SPTB or term. The first minute Apgar score of 0 – 3 was 7.1% and reduced to 3.5% in the fifth minute. The 7 – 10 Apgar scores increased from 67.4% in the first minute to 79.3% in the fifth minute. The association between four genetic markers (AGTR2 rs5950491, WNT4 rs56318008, EEFSEC rs2955117 and ADCY5 rs9861425) identified in the European genome-wide association studies to be associated with gestational duration was not replicated in this study. The WNT4 rs56318008 (C/T) was found to be monomorphic with the CC genotype among Ghanaian women. The T allele frequency of the SERPINH1- 656 (C/T) SNP was 0.1 in among Ghanaian women. The T allele of the SERPINH1- 656 (C/T) SNP and associated with over 2 days decrease in gestational duration, and 63% and 90% increased risk of SPTB and PPROM respectively in Ghanaian women. The SERPINH1- 656 (C/T) SNP was also associated with 67% and 77% increased risk of SPTB based on the heterozygous and additive models respectively. The TT genotype frequency was 0.0038 in the Ghanaian women population. It was observed only among women with SPTB, specifically those with PPROM. The TT genotype of the SERPINH1- 656 (C/T) SNP reduced the expression on SERPINH1 in the placenta at a fold change of 0.77 compared with 0.94 for the CT (cases) as well as 1.07, 1.20 and 1.05 for the CT (controls), CC (control) and CC (cases) respectively. However, the reduced TT expression was not significantly different from the other genotypes (p = 0.12). Generally, the MMP1 (-1607 1G/2G) SNP was not associated with SPTB except the heterozygous 1G/2G genotype that provided a 34% suggestive risk to SPTB but did not reach statistical significance (p < 0.08). Two out of 3 Ghanaian women with SPTB do not know whether they were born preterm or term. Over 7 out of 10 Ghanaian women with SPTB do not know whether either their mother and/or sister(s) was born preterm or term. Conclusion: SPTB among Ghanaian women is influenced by both genetic and environmental factors. SPTB is independently influenced by maternal factors like age, antenatal visits and psychological distress. Signs of reduced rate of intrauterine development of Ghanaian foetuses is evident in the 29th week of gestation. The T allele of SERPINH1- 656 (C/T) could be a genetic risk associated gestational duration with PPROM occurrence in Ghana. A multi-omic study of SPTB will provide a very comprehensive understanding of the aetiology of SPTB in Ghana. Additionally, a comprehensive transgenerational study embedded with lifestyle characteristics is needed to better understand how SPTB runs through families in Ghana. Additionally, a larger nationwide population-based study is needed to provide much information about the foetal growth dynamics of Ghanaians.