Abstract:
The burgeoning obesity epidemic has become as profound a health problem as under-nutrition on the global scale. With the general rise of obesity, there has been a parallel vast increase in the incidence of overweight and obese women of reproductive age. There are consequent increasing rates of serious maternal, fetal and neonatal complications secondary to obesity. Using retrospective analysis of prospectively collected data from the international multicentre Screening for Pregnancy Endpoints (SCOPE) study, and of routinely collected data from National Women’s Health, Auckland, New Zealand from 2006 to 2009, we investigated the role of obesity as a risk factor associated with three common adverse pregnancy outcomes in obese nulliparous women: Caesarean section, postpartum haemorrhage and pre-eclampsia. We reported two novel findings relating to Caesarean section. Firstly, being overweight or obese is an independent risk factor for Caesarean delivery in labour, but this elevated risk is confined to the first stage of labour. Obese women who progress to the second stage of labor are just as likely to birth vaginally as women with normal BMIs. Secondly, we found that although obesity is also associated with hyperlipidaemia and cholesterol inhibits myometrial contractility in vitro, elevated maternal serum cholesterol in early pregnancy is not a risk factor for first stage Caesarean for failure to progress in overweight or obese women. We found that nulliparous obese women have a twofold increase in risk of major postpartum haemorrhage (≥1000mls) compared to women with normal BMI regardless of mode of birth. Higher rates of postpartum haemorrhage among obese women are not attributable to their higher rates of Caesarean delivery. Finally we found that risk factors present at 14-16 weeks of gestation in obese nullipara that were associated with development of pre-eclampsia share similarities with those implicated in cardiovascular disease. This may in part explain the linkage between preeclampsia and later cardiovascular disease. We have identified novel factors that will assist with risk assessment, and clinical management of obstetric care for obese women. Our findings provide direction for future research to assist in reduction of adverse pregnancy outcomes for obese women.