Is time-interval between mini-pill ingestion and breastfeeding essential?

Distribution of progesterone receptor immunoreactivity in the midbrain and hindbrain of postnatal rats

“…The perinatal female ovary begins to secrete progesterone after the first week of life (Schlegel et al, 1967;Quattropani and Weisz, 1973;Greco and Payne, 1994). However, the developing brain of both males and females may be exposed to significant levels of progesterone deriving from maternal sources (Pepe and Rothchild, 1974;Martin et al, 1977;Sanyal, 1978;Betrabet et al, 1987;Toddywalla et al, 1995;Quadros and Wagner, 1999) or through the de novo synthesis of progesterone from cholesterol within the developing brain itself (Compagnone et al, 1995a,b;Kohchi et al, 1998;Ukena et al, 1998Ukena et al, , 1999.…”

“…Although the perinatal ovary is quiescent until the second week of life (Schlegel et al, 1967;Quattropani and Weisz, 1973;Greco and Payne, 1994), there appear to be at least two alternate sources of progesterone: the maternal ovary and/or de novo synthesis within the developing brain itself. Maternal progesterone levels are high, not only during gestation, but also during lactation (Pepe and Rothchild, 1974;Martin et al, 1977;Sanyal, 1978;Quadros and Wagner, 1999) and progesterone may pass to neonates through mother's milk (Betrabet et al, 1987;Toddywalla et al, 1995). In addition, the perinatal rodent brain expresses all the enzymes necessary for the de novo synthesis of progesterone from cholesterol (Compagnone et al, 1995a;Kohchi et al, 1998;Ukena et al, 1998;Zwain and Yen, 1999), potentially producing locally high concentrations of progesterone within specific brain regions.…”

Progesterone Receptors and Neural Development: A Gap between Bench and Bedside?

“…Recent evidence suggests that progestins in contraceptives can enter mother's milk, can be detected in the serum of breast-fed infants (2)(3)(4)15), and may influence the infant hypothalamo-pituitary-thyroid axis (16). Yet a recently published meta-analysis of clinical reports concluded that evidence regarding the use of hormonal contraceptive during lactation is limited and of poor quality and stressed the urgent need for a properly conducted clinical trial in this field (17).…”

“…Preliminary studies from our laboratory demonstrate that plasma P levels in mothers and fetuses are positively correlated at the end of gestation and suggest that P from maternal circulation can bind to nuclear PR within the fetal male rat MPN (20). In humans, progesterone has been isolated and quantified in mother's milk (51), and it has been demonstrated that progestins in milk can pass to breast-fed neonates (2)(3)(4). In addition to potential maternal sources of P, the perinatal rodent brain expresses all the enzymes necessary for the de novo synthesis of P from cholesterol (52)(53)(54)(55), potentially producing locally high concentrations of P within specific brain regions.…”

“…In addition, breast-fed neonates may be exposed to progestins from maternal contraceptive use (2)(3)(4), and clinical trials in which premature infants are treated with progesterone and estradiol are underway in Europe (5). Yet very little is known about the effects of progestin exposure on the developing brain.…”