Thyroid hormones are important in the development of the fetus and the placenta as well as in maintaining maternal wellbeing. Thyroid disorders are common in the population as a whole, particularly in women, and therefore are common during pregnancy and the puerperium. Biochemical derangement of thyroid function tests are present in approximately 2.5–5% of pregnant women.

Polycystic ovary syndrome (PCOS) is a common hormonal disorder affecting around 5–8% of women of reproductive age. It has a variable clinical spectrum including hyperandrogenism, menstrual abnormalities, polycystic ovaries and metabolic features like diabetes mellitus, obesity and dyslipidaemia. The manifestation of PCOS and its impact especially on reproductive function and pregnancy are profoundly affected by associated features of obesity/raised body mass index and metabolic syndrome.

Premature rupture of membranes (PROM) is a major cause of perinatal mortality and morbidity associated with preterm delivery in a third of cases. Fetal survival is even more compromised when the membranes rupture early in the second trimester (very early PROM). Survival is associated with problems of delivery of the very preterm fetus as well as associated risks of feto-maternal infection. In the context of studies of amnioinfusion, very early rupture of membranes is defined as rupture between 16 and 26 weeks of pregnancy.

The most common maternal risk factor associated with neonatal complications during delivery is obesity. Although gestational diabetes mellitus (GDM) occurs in 5–10% of the pregnant population, obesity, by virtue of its prevalence, far outpaces GDM as the most important underlying risk factor for increased fetal adiposity. The mechanisms underlying maternal insulin resistance may play an important role in the diversion of excess fuels to the fetus. Maternal adipose depots increase in early pregnancy, followed by increased adipose tissue lipolysis and subsequent hyperlipidaemia, which mainly corresponds to increased triglyceride levels (TG). A positive correlation between maternal TG and infant body weight or fat mass has been found in both GDM and non-GDM obese women. Increased oxidative stress, altered adipokines, and inflammatory cytokines have also been found in obese pregnant women, suggesting an adverse metabolic outcome even in normoglycemic conditions.