Pregnancy

Depending on different cultures, between 5% and 60% of women who become pregnant while still breastfeeding continue to breastfeed during pregnancy. ^{(Çınar 2022, Molitoris 2019, López 2017, Merchant 1990)}

No differences have been found in the duration of pregnancy, newborn weight and subsequent growth, or in the rate of miscarriage between healthy, well-nourished pregnant women who continue breastfeeding and those who do not. ^{(Stalimerou 2023, Molitoris 2019, López 2017, Shaaban 2015, Pareja 2015, Ayrim 2014, Cetin 2014, Madarshahian 2012, Ishii 2009, Moscone 1993)}

A retrospective study with many limitations showed an increased risk of miscarriage with exclusive breastfeeding during pregnancy but not with breastfeeding together with complementary feeding ^{(Molitoris 2019)}, which could actually be explained by the shorter spacing between pregnancies.

Breastfeeding during pregnancy does not produce adverse results in either the mother or the fetus in a normal low-risk pregnancy, although it may generate a nutritional burden for the mother. ^(Minh 2021)

Nutritional, energy, mineral and vitamin needs are very high in pregnancy and more so during breastfeeding ^{(Molitoris 2019)}, which is why less weight gain, decreased hemoglobin levels and other problems have been reported in women who breastfeed during pregnancy, especially in economically disadvantaged populations. ^{(Shaaban 2015, Ayrim 2014; Marquis 2003 and 2002, Siega 1993)}

By ensuring the necessary extra dietary intake, breastfeeding is considered compatible and safe in a new pregnancy (CLM 2012, HWA 2009). The Working Group on Breastfeeding of the Italian Association of Perinatal Medicine have positioned themselves in this regard. ^{(Cetin 2014)}

Although nipple stimulation has been used to elicit cervical ripening and induce labour ^{(Kavanagh 2005)}, there is no evidence that oxytocin released during breastfeeding can induce preterm labour or miscarriage ^{(Molitoris 2019)}, as the oxytocin peak is not sufficient and because the uterine oxytocin receptors are not complete until the end of pregnancy in the uterus. ^{(López 2017)}

Breastfeeding has historically been a method of spacing pregnancies, but, outside the first 6 months and exclusively and intensively (LAM method), it cannot be considered a contraceptive method nor is it at odds with planning a new pregnancy. ^{(Tikka 1998, Short 1991, Chao 1987)}

Possible changes in milk taste, increased breast tenderness, a woman's sense of refusal to continue breastfeeding, cultural taboo, self-beliefs, social pressures, advice from preofessionals, a decrease in milk production, and spontaneous weaning of the infant are factors that have been implicated in the increased frequency of weaning that occurs during pregnancy. ^{(Çınar 2022, Moscone 1993)}

If breastfeeding continues throughout the pregnancy, the breast returns to producing colostrum around the time of delivery and the immediate postpartum period.