Does breastfeeding improve maternal heart health? Probably not.

Breastfeeding rates have risen dramatically over the past 50 years and NONE of the predicted benefits for infant health have come to pass.

Why not?

Because breastfeeding is SOCIALLY patterned (breastfeeding is closely associated with higher socio-economic status) and most of the purported benefits of breastfeeding are actually benefits of maternal wealth, education and access to healthcare.

Lately the focus has been on claiming maternal benefits of breastfeeding. But those probably don’t exist either because breastfeeding is also MEDICALLY patterned. Women who are more likely to have difficulty breastfeeding for medical reasons are also more likely to develop serious illness later in life.

That’s the message from a new evaluation of claims that breastfeeding protects against maternal heart disease. The paper is Adverse Pregnancy Outcomes: The Missing Link in Discovering the Role of Lactation in Cardiovascular Disease Prevention published in Journal of the American Heart Association.

The authors reference a paper published earlier this year that received a lot of media attention:

[T]he January 2022 issue of the Journal of the American Heart Association (JAHA) included the article by Tschiderer and colleagues titled, “Breastfeeding Is Associated With a Reduced Maternal Cardiovascular Risk: Systematic Review and Meta‐Analysis Involving Data from 8 Studies and 1 192 700 Parous Women.”1 The compilation and synthesis of data from over 1 million women is a valuable contribution to the literature. The primary findings were that a history of any duration of breastfeeding was associated with 11% to 17% reduction in the relative risks of later life adverse cardiovascular outcomes … for coronary heart disease; HR, 0.88 … for stroke; and HR, 0.83 … for fatal CVD),1 after accounting for reproductive and sociodemographic factors.

That study did not account for an important confounding variable, adverse pregnancy outcomes like pre-eclampsia, gestational diabetes or premature birth.

These pregnancy complications are established risk factors for both future CVD in women and also  for difficulty breastfeeding.

In other words reduced breastfeeding doesn’t cause future maternal cardiovascular disease, it predicts it.

Prepregnancy obesity, chronic conditions, and certain APOs [adverse pregnancy outcomes], especially preeclampsia and preterm delivery, can interfere with breastfeeding initiation and lead to delayed onset of lactogenesis and earlier cessation, as well as increased CVD risk in later life.

The implications don’t merely undercut the claimed benefit of breastfeeding in preventing maternal cardiac disease, they undercut the unquestioned assumptions about breastfeeding that have been promoted by the lactation profession.

Lactation professionals assume — and have aggressively advocated the idea — that every woman is biologically capable of successful breastfeeding. To the extent that women experience difficulty breastfeeding, lactation professionals ascribe it to malingering (“perceived insufficient breastmilk”), formula advertising or infant anatomical abnormalities (tongue-ties).

But difficulty breastfeeding has biological markers (breastmilk sodium concentrations), genetic markers and associations with adverse pregnancy outcomes.

…Maternal and neonate medical complications related to clinical outcomes (ie, prematurity) and physiologic effects (ie, delayed onset of lactogenesis) of APOs are recognized barriers to lactation success… Thus, the findings of a consistent protective association between lactation and adverse CVD outcomes based on the summary risk estimates … leave open the question of reverse causation, effect modification, or confounding.

Just as we find that nearly all predicted infant benefits of breastfeeding disappear when maternal socio-economic status is taken into account, we may find that nearly all predicted maternal benefits of breastfeeding disappear when maternal adverse pregnancy outcomes are taken into account. That’s because the same factors that lead to maternal chronic diseases also lead to breastfeeding difficulties.

In order to understand what is going on, we need a massive realignment in the way that we think about breastfeeding:

Difficulty breastfeeding is NOT the result of cultural and psychological factors but rather of MEDICAL factors.

Instead of blaming “society” and women themselves for breastfeeding difficulties we should be exploring the biology of insufficient breastmilk and its implications for women’s health overall.