Thirty-eight infants admitted to a neonatal intensive care unit because of pneumonia (14 patients) and pulmonary maladaption syndrome (PMA) (24 patients) were included in the study. Samples of potentially pathogenic, facultatively anaerobic bacteria were taken from the external ear, blood, throat, nasopharynx, umbilicus and gastric aspirates of the children, and from urethra and cervix of the mothers. Group B streptococci (GBS) and Escherichia coli were the only potentially pathogenic bacteria isolated from the infants. Out of 14 infants with pneumonia 11 (79%) harboured one of these bacteria, in contrast to 3 out of 24 (13%) with PMA (P less than 0.001). GBS was found in 8/14 infants with pneumonia and in 1/24 infants with PMA (P less than 0.001). The respective frequencies for Escherichia coli were 3/14 and 2/24 (not significant). The infant and/or the mother in 10/14 pneumonia cases harboured GBS, in contrast to 4/24 pairs in the PMA group (P less than 0.001). The levels of antibodies against GBS in sera of mothers to infants with pneumonia did not differ from the antibody levels in control sera (parturient GBS-carriers giving birth to healthy infants). The results gave evidence for an important manifestation of neonatal GBS-infection: pneumonia without septicemia. The incidence of the disease is estimated to be 1:25 parturient GBS-carriers. Finally, maternal fever, gestational age above 42 weeks, more severe respiratory difficulties and the occurrence of severe changes in fetal heart rate during the first stage of labour were found to be typical characteristics of pneumonia, as compared to PMA.

A method has been developed for the detection in human sera of antibodies to surface antigens of group B streptococci (GBS), types Ia, Ib, or III. The sera were absorbed with GBS type II and then added to a suspension of GBS of the type against which antibodies were to be measured. After incubation and washing of the bacteria, the antibodies present on the surface of the cells were quantitated with radiolabelled protein A. Antibodies of IgG class were detected, probably specific for types Ia, Ib, or III, with the exception that the Ib GBS suspension used could detect some antibodies to type Ia. With this method it was found that 6/7 mothers to infants with GBS septicemia had low levels of serum antibodies to the infant's type of GBS. Urogenital carriers of GBS, giving birth to neonatally healthy infants, had higher serum antibody levels against the colonizing type.

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Urethral and cervical specimens were obtained from 786 parturients during labour. 126 women (16%) were found to be urogenital carriers of group B streptococci (GBS). Bacteriological specimens were also obtained from the throat, umbilicus and external auditory canal of their 786 infants immediately after birth, and from 671 of the infants staying at the maternity unit 4 days later. 51% (64/126) of the infants born to GBS carriers were culture-positive for GBS immediately after birth. Only 27% (6/22) of the infants born to women who were GBS culture-positive in the urethra but not in the cervix contracted GBS at the delivery, in contrast to 59% (58/85) of the infants born to combined urethral and cervical carriers (P less than 0.05). This difference in colonization rate was not related to differences in levels of antibodies to the type of GBS carried by the individual parturient. On day 4, 13% (90/671) of the infants in the maternity unit were colonized with GBS. 39% of them were colonized at birth from their mother, 12% were culture negative at birth but had become colonized by day 4 with the same type of GBS as that isolated from the urogenital tract of the mother, and 37% were GBS positive on day 4 but culture-negative at birth and the mother's specimens did not reveal GBS. The distribution of serotypes among these infants was identical with that found among the other colonized infants, indicating that they might have contracted their GBS from the other infants in the maternity unit.

The obstetrical significance of maternal urogenital carriage of group B streptococci (GBS) was investigated in a prospective study comprising 799 parturients and their infants. 128 mothers were GBS carriers. Fetal heart rate recording showing abnormal baseline frequency and concomitant late decelerations during delivery were found in 6 infants born of GBS carriers (5%) and in 7 (1%) of non-carriers (P < 0.01). The pH of fetal blood was determined in 14 (11%) GBS carriers and in 53 (8%) non-carriers. 6/14 (43%) infants of GBS carriers had pH values below 7.20, in contrast to 4/53 (8%) of the non-carrier group (P < 0.01). Mothers of infants showing signs of intrauterine asphyxia had the same amount of antibodies to GBS as mothers of infants without signs of asphyxia. Among the GBS carriers, 11/128 (9%) were delivered later than the 42nd week of pregnancy. A smaller proportion of non-carriers, 21/671 (3%), were delivered postterm (P < 0.01).