During the study period, 209 women of childbearing age (15-44 years) were admitted to an intensive care unit with confirmed 2009 H1N1 infection. Of these, 64 (31%) were either pregnant or post partum; 57 were admitted to an intensive care unit in Australia and seven to an intensive care unit in New Zealand.
At the time of onset of symptoms of influenza, 10 of these 64 women were at less than 20 weeks’ gestation, 49 were at 20 weeks or more, and five were post partum. The estimated number of women of childbearing age in Australia and New Zealand during the study period was 5
000, giving 70
000 women weeks—that is, weeks of potential pregnancy over the 13 weeks of the pandemic. Overall, there were 1
000 women weeks of gestation at less than 20 weeks, 1
000 women weeks of gestation at 20 weeks or more, and 358
000 women weeks post partum.
The overall risk of admission to an intensive care unit for non-pregnant women of childbearing age was 1 in 35
300 compared with 1 in 14
600 for gestations less than 20 weeks, 1 in 2700 for gestations of 20 weeks or more, and 1 in 5500 for the postpartum period. Compared with non-pregnant women of childbearing age, pregnant women with a gestation of 20 weeks or more had a 13-fold greater risk of admission to an intensive care unit as a result of 2009 H1N1 infection (relative risk 13.2, 95% confidence interval 9.6 to 18.3). The corresponding risk for postpartum women was 6.4 (2.6 to 15.7) and for women with a gestation of less than 20 weeks was 2.4 (1.3 to 4.6). Overall, compared with non-pregnant women of childbearing age the relative risk of women who were pregnant or post partum being admitted to an intensive care unit with 2009 H1N1 infection was 7.4 (5.5 to 10.0).
Figure 1 summarises the maternal and perinatal outcomes after admission to an intensive care unit. Of the 64 women admitted to an intensive care unit, 40 (63%) were pregnant, 22 (34%) were post partum, and 2 (3%) had miscarried. Twenty six women (41%) were discharged from the intensive care unit with ongoing pregnancy, of whom 23 (36%) had given birth at last follow-up. Three women should have delivered according to dates but could not be followed up as of 22 February 2010. Admission to an intensive care unit post partum or after miscarriage occurred a median of 0 (range 0-8) days after delivery, and 19 of 24 women (79%) had onset of influenza symptoms while pregnant. Figure 2 shows the duration of gestation at onset of influenza symptoms for women categorised as having had a miscarriage, being post partum at admission to an intensive care unit, delivering while in the unit, or being discharged from the unit with an ongoing pregnancy.
Fig 1Outcomes after admission to intensive care unit
Fig 2Gestation at onset of influenza symptoms in women, according to pregnancy status
Tables 1 and 2 list the characteristics, influenza syndromes and onset of symptoms, management in intensive care, and outcome of pregnant or postpartum women admitted to an intensive care unit with 2009 H1N1 infection. Thirteen of 57 patients (20%) in Australia were Australian Aboriginal or Torres Strait Islanders. Admission to an intensive care unit was more common in this group than in non-indigenous women (relative risk 6.2, 95% confidence interval 3.8 to 9.9). Admission to an intensive care unit was also more common among Maori and Pacific Islander women compared with other pregnant women (2.3, 1.4 to 3.7). Of 59 women with available data, 25 (39%) had a body mass index of more than 30 and 13 (20%) an index or more than 35. Overall, 36 women (56%) had a documented coexisting illness, of whom 21 (33% of total) had asthma. Other coexisting illnesses included documented valvular or congenital heart disease in four women (6%), depression requiring drugs in three (5%), and diabetes and essential hypertension in two women (3%). Sixteen women (25%) developed a new obstetric problem during their pregnancy, of whom six (9%) developed gestational diabetes and seven (11%) pregnancy induced hypertension or pre-eclampsia. No women had been immunised against seasonal influenza.
Table 1 Characteristics of pregnant or postpartum women admitted to intensive care units with 2009 H1N1 infection. Values are numbers (percentages) unless stated otherwise
Table 2 Influenza syndromes and onset of symptoms, intensive care management, and outcome of pregnant or postpartum women admitted to intensive care unit with 2009 H1N1 infection. Values are numbers (percentages) unless stated otherwise
Forty four women (69%) were mechanically ventilated for a median of nine days (range 1-45 days), and nine (14%) were treated with extracorporeal membrane oxygenation. Eighteen women (28%) received corticosteroids for reasons other than fetal lung maturation and 81% received oseltamivir in the intensive care unit (no other neuraminidase inhibitors were used).
Seven women (11%) died from 2009 H1N1 influenza. All seven had viral pneumonitis or acute respiratory distress syndrome secondary to 2009 H1N1 infection. In addition, two had pulmonary haemorrhage and one each had septic shock, viral encephalitis, and the syndrome of haemolysis, elevated liver enzymes, and low platelets. All were mechanically ventilated and three were treated with extracorporeal membrane oxygenation. Four received corticosteroids. All were treated with oseltamivir. Six of the nine women (67%) treated with extracorporeal membrane oxygenation survived.
As of 22 February 2010, 59 of the women were known to have given birth to 60 babies of at least 20 weeks’ gestation; 56 were live born and four were stillbirths. There was one set of liveborn twins. Of the 22 postpartum women, 14 (64%) had had an emergency caesarean section and eight (36%) had spontaneous vaginal deliveries. Fourteen women (26%) gave birth during their stay in an intensive care unit, 13 (93%) by emergency caesarean section. Non-mutually exclusive indications for delivery that occurred in women while in an intensive care unit were maternal hypoxaemia in 13 (93%), maternal haemodynamic instability in 8 (57%), and concern for fetal wellbeing in 3 (21%). Three of the 14 women (21%) requiring caesarean section while in the intensive care unit died. In only one case was concern for fetal wellbeing the sole indication for delivery while in the intensive care unit. Of 23 women who delivered after discharge from intensive care, 17 (74%) had vaginal deliveries and six (26%) caesarean sections, of which three were elective and three were during labour. Seven women (16%) had postpartum haemorrhage (blood loss >1500 ml).
Table 3 describes the perinatal outcomes of the 60 babies. Eleven (18%) had gestations between 32 and 37 weeks, and 11 (18%) between 20 and 32 weeks. Ten (17%) weighed between 1500 g and 2500 g at birth, whereas eight (13%) weighed less than 1500 g. The birth weight of three male neonates (5%) was below the 10th centile for gestational age for males. Thirty two (57% of 56 liveborn babies) were admitted to a neonatal intensive care unit or special care nursery, including three babies born after the mother was discharged from the intensive care unit, for a median stay of 18 days (range 1-79 days). Twenty one (38% of 56 liveborn babies) required continuous positive airway pressure ventilation or endotracheal intubation with positive pressure ventilation. Of 20 neonates tested, two were positive for 2009 H1N1 virus infection. Three infants died (two neonates and one post-neonatal infant), all related to complications of prematurity, hypoxic encephalopathy, or both.
Table 3 Perinatal outcomes. Values are numbers (percentages) unless stated otherwise