The purpose of this study is to investigate what proportion of obese women will have a self-reported delay in lactogenesis II ("breastmilk coming in") compared to women with a normal weight. We hypothesize that obese women will have an absolute 20% increase in delayed lactogenesis II.

We will compare two group of women for delayed lactogenesis II, one group with obese women (BMI>30) and one group of women with a normal weight (BMI<30).

The secondary objective is to assess what other factors influence the self-reported delayed lactogenesis II.

Lactogenesis I occurs during pregnancy (midpregnancy and beyond), when the mammary glands becomes sufficiently differentiated to secrete small quantities of specific milk components. Lactogenesis II is defined as the onset of plentiful milk secretion and typically occurs between 30-40 hours post delivery. It is typically described by women as a sense of fullness and leakage of milk which is subjectively reported between 50-73 hours post delivery. The incidence of delayed lactogenesis II ranges from 17-44%.

The risk of neonatal weight loss is up to 7 times greater for exclusively breastfed infants of women who experience delayed lactogenesis II as compared to women who experience typical onset lactogenesisII. In a qualitative study of 114 lactating women, increasing BMI was significantly associated with maternal perceptions of delayed onset of lactogenesis II.

The United States Breastfeeding Committee supports exclusive breastfeeding for the first 6 months of life because it "may exert a small but positive influence in reducing the risk of obesity in childhood and later in life…" Breastfeeding has also been associated with decreased risk of maternal morbidities such as type 2 diabetes, subclinical cardiovascular disease and less abdominal visceral adiposity. Given that prolonged breastfeeding improves the overall health of the mother infant dyad, it is critical to obtain a better understanding of those factors predictive of successful breastfeeding outcomes.

At University of South Florida our clinics serve an ethnically diverse population which would benefit from directed efforts at improving breastfeeding. Before we can undertake such a plan we need to assess the contemporary factors impacting lactogenesis.

We plan to prospectively enroll 186 pregnant women into a protocol to examine factors associated with delayed lactogenesis. Ninety-three women will have a BMI of 30 or higher at the time of delivery and the other 93 women will have a BMI ≤ 29 at the time of delivery.

Inclusion Criteria:

• intend to attempt breastfeeding
• Expecting a live-born infant
• Singleton pregnancy
• English or Spanish language fluency
• Delivered at fullterm gestation

Exclusion Criteria:

• Multiple gestation delivery
• Delivered pre-term (<36weeks and 6 days of gestation)
• Not admitted to Mother Baby Unit (MBU) (ie admitted to intensive or special care unit or to Labor & Delivery Unit for postpartum monitoring)
• Mother did not initiate breastfeeding within 12 hours.
• No telephone access
• History of breast reduction or enlargement surgery
• Planning to formula feed from birth (no intention to breastfeed or try breastfeeding).

We plan to prospectively enroll 186 pregnant women into a protocol to examine factors associated with delayed lactogenesis. Ninety-three women will have a BMI of 30 or higher at the time of delivery and the other 93 women will have a BMI ≤ 29 at the time of delivery.