A Screaming Newborn, Newfound Exhaustion, and a Sensitive Period?

Wei Perng, PhD, MPH

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​Sitting the month. Most women of Asian or Middle Eastern descent can rattle off a list of things a new mother must not do in the month following delivery. The most common examples include: taking a bath, washing her hair, drinking cold beverages or foods, touching cold water, washing dishes, lifting heavy items (probably an all-around good idea anyway), sitting in front of a fan… and heaven forbid, do not even think about leaving the house. In Mandarin, we call this “sitting the month.” The motivation behind these rules, which have been featured on NPR, is to protect the recuperating mother from environments that may leave her vulnerable to chronic conditions later on. As wacky as these ideas seemed to me as a child, I recently began to wonder whether the postpartum period is, indeed, a sensitive period for a new mother’s future well-being. While there is little scientific research on this topic, the postpartum period is undoubtedly a time of rapid change in hormones, weight, and lifestyle that could set the tone for health down the road.

​Hormones and mood disorders.  Shortly after delivery, estrogen and progesterone take a plunge from the equivalent to taking a hundred birth control pills per day.  By the end of the first week, these hormones return to pre-pregnancy levels, causing some women to feel a little blue. Prolactin and oxytocin surge to encourage lactogenesis, which may offset the emotional low of the estrogen and progesterone drop. For many women, thyroid hormone can increase or decrease due to inflammation of the thyroid gland and changes to liver function. And the list goes on.  The magnitude and duration of hormonal fluctuations may contribute to future disease risk. Epidemiological studies and rodent models indicate that larger fluctuations in female steroid hormones correlate with emergence of mood disorder symptoms and episodes, and one instance of postpartum depression is correlated with future episodes of depressive disorders.

Weight retention and cardiometabolic disease. Most women lose weight after pregnancy, retaining an average of 0.5 - 1.5 kg at 6-18 months postpartum. However, a non-negligible 13% to 20% remain >5 kg heavier than their pre-pregnancy weight. This is worrisome because excess weight after childbirth tends to be deposited centrally as metabolically active fat. Additionally, retention of weight within the first year after delivery could lead to long-term obesity, contribute to development of obesity-related illnesses like heart disease and diabetes, and could contribute to additional weight gain in subsequent pregnancies.

Lactation and metabolism. We’ve all heard the mantra, “Breast is best.” Not only is breastfeeding good for your baby, but breast milk production encourages mobilization of weight gained during pregnancy and has beneficial effects on metabolism. In a study of 522 postpartum women, breastfeeding mothers had better insulin sensitivity than those who were formula-feeding. To rule out reverse causation (i.e., healthier women with better glycemic control are more likely to breastfeed), a subsequent study compared blood glucose levels of lactating women who breastfed vs. did not breastfeed their infants after an oral glucose tolerance test (OGGT). Women who breastfed during the OGTT had lower post-load glucose and insulin than their counterparts, suggesting that lactation is independently associated with mobilization of glucose. Although longer term studies are required to link glycemic control during the postpartum period to future health outcomes, these studies do indicate some short-term benefits of breastfeeding for a woman’s metabolic health. Additionally, breastfeeding has been consistently found to be protective against breast cancer via its effects on mammary gland cell differentiation, hormonal changes, and its impact on circulating lipids (discussed here).

So, can I take a bath and eat a bowl of ice cream? I cannot say for sure, but I personally took a shower upon returning home, and I touched/drank a lot of ice water (just don’t tell my mom). However, a key take-away message is that many of the physiological changes that occur during the postpartum period can be influenced by diet and lifestyle. For example, magnesium,  fatty acids, and physical activity can modulate hormonal fluctuations. In similar vein, a healthy diet, maintaining an active life style, and breastfeeding can help shed pounds and encourage mood-enhancing hormones like oxytocin and endorphins. Given that current literature focuses on acute consequences of circumstances and lifestyle during this timeframe for the mother and baby, there is need for investigations linking maternal lifestyle and condition during the postpartum to long-term health outcomes.