Placental weight and efficiency in relation to maternal body mass index and the risk of pregnancy complications in women delivering singleton babies

• Published in: Placenta (Eastbourne) Vol. 33; no. 8; pp. 611 - 618
• Main Authors: Wallace, J.M, Horgan, G.W, Bhattacharya, S
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-08-2012; Elsevier
• Subjects: Adult; Biological and medical sciences; Cohort Studies; Databases, Factual; Embryology: invertebrates and vertebrates. Teratology; Female; Fundamental and applied biological sciences. Psychology; Humans; Hypertrophy; Internal Medicine; Maternal body mass index; Obesity; Obesity - physiopathology; Obesity, Morbid - physiopathology; Obstetrics and Gynecology; Organ Size; Overweight - physiopathology; Placenta - pathology; Placenta - physiopathology; Placental efficiency; Placental Insufficiency - epidemiology; Placental Insufficiency - etiology; Placental Insufficiency - pathology; Placental Insufficiency - physiopathology; Placental weight; Placentation; Pregnancy; Pregnancy complications; Pregnancy Complications - epidemiology; Pregnancy Complications - etiology; Pregnancy Complications - pathology; Pregnancy Complications - physiopathology; Retrospective Studies; Risk Factors; Thinness - physiopathology; United Kingdom - epidemiology; Young Adult; Obesity; Maternal body mass index; Placental weight; Placental efficiency; Pregnancy complications; Human; Fetal membrane; Body weight; Infant; Pregnancy; Body mass index; Vertebrata; Mammalia; Placenta; Mother; Efficiency; Risk factor; Complication; Female
• ISSN: 0143-4004; 1532-3102
• DOI: 10.1016/j.placenta.2012.05.006

Abstract Herein we report placental weight and efficiency in relation to maternal BMI and the risk of pregnancy complications in 55,105 pregnancies. Adjusted placental weight increased with increasing BMI through underweight, normal, overweight, obese and morbidly obese categories and accordingly underweight women were more likely to experience placental growth restriction [OR 1.69 (95% CI 1.46–1.95)], while placental hypertrophy was more common in overweight, obese and morbidly obese groups [OR 1.59 (95% CI 1.50–1.69), OR 1.97 (95% CI 1.81–2.15) and OR 2.34 (95% CI 2.08–2.63), respectively]. In contrast the ratio of fetal to placental weight (a proxy for placental efficiency) was lower ( P  < 0.001) in overweight, obese and morbidly obese than in both normal and underweight women which were equivalent. Relative to the middle tertile reference group (mean 622 g), placental weight in the lower tertile (mean 484 g) was associated with a higher risk of pre-eclampsia, induced labour, spontaneous preterm delivery, stillbirth and low birth weight ( P  < 0.001). Conversely placental weight in the upper tertile (mean 788 g) was associated with a higher risk of caesarean section, post-term delivery and high birth weight ( P  < 0.001). With respect to assumed placental efficiency a ratio in the lower tertile was associated with an increased risk of pre-eclampsia, induced labour, caesarean section and spontaneous preterm delivery ( P  < 0.001) and a ratio in both the lower and higher tertiles was associated with an increased risk of low birth weight ( P  < 0.001). Placental efficiency was not related to the risk of stillbirth or high birth weight. No interactions between maternal BMI and placental weight tertile were detected suggesting that both abnormal BMI and placental growth are independent risk factors for a range of pregnancy complications.