*3.2.1 In mother*

Pregnancy is an anabolic state where adequate energy stores are required to cater to the nutritional demands of the growing fetus. However, pregnancy is a state of leptin resistance and the role of leptin in pregnancy deviates considerably from its classical role of controlling food intake [15, 16].

The functions can be elaborated as follows (**Figure 1**) [8, 17]:



### *3.2.2 In fetus*

Fetal leptin is predominantly fetal in origin and is present in fetal blood from 18 weeks of gestation [8, 18]. Maternal leptin does not cross the placenta to affect fetal functions due to its high molecular weight [19].

However, the umbilical cord blood leptin concentrations correlate strongly with fetal fat mass serving as a good indicator for the same [8, 10, 11, 20]. Fetal leptin levels increase as gestational age increases [21]. Female foetuses have higher serum leptin levels than their male counterparts due to the suppression of leptin by testosterone in males [22].

Leptin receptors have been reported to be expressed in fetal tissues, for example, bone, kidney, and hypothalamus and fetal leptin supports fetal endocrine functions, for example, angiogenesis and erythropoiesis.
