Why do women in the private sector have shorter pregnancies in Brazil?: Left shift of gestational age, caesarean section and inversion of the expected disparity - Diniz, Carmen Simone Grilo; Miranda, Marina Jorge de; Reis-Queiroz, Jéssica; Queiroz, Marcel Reis; Salgado, Heloisa de Oliveira (Journal of Human Growth and Development, 2016)