It appears that the earlier a pregnant woman is afflicted with the Zika virus, the more likely it is her baby may suffer from brain damage, a Brazilian doctor has observed.
Dr Heron Werner, a specialist in gynaecology, obstetrics and foetal medicine at Alta Excelencia Diagnostica, said that he has seen six pregnant women with Zika since late last year.
Four of them developed symptoms including fever, rashes, joint pains and conjunctivitis in their first trimesters. Through ultrasound, Dr Werner detected microcephaly in their foetuses by the time they were in their third trimesters.
Microcephaly is a condition marked by abnormally small heads in newborn babies that can result in developmental problems.
Dr Werner could also pick up brain atrophy (shrinking of the brain), calcium deposits and dilation of ventricles (connecting cavities) of the brain. All these would contribute to brain damage, which then affect the child's development, among other things.
Yet he could not detect any abnormalities in the foetuses of the other two women who had Zika at later stages of their pregnancy- 16 and 27 weeks of gestation. A diagnosis is made when newborn babies have their head sizes measured at birth.
Dr Pedro Octavio de Britto Pereira, an obstetrician at Casa de Saude Sao Jose who is not looking after these six women, agreed that this seems to suggest that "the most serious cases occur when the disease affects the pregnant woman in the first trimester".
But their observation has yet to be proven in clinical studies.
Zika has spread rapidly through Latin America and the Caribbean, with Brazil the worst hit, followed by Colombia.
Last Monday, Brazilian researchers said they discovered Zika in the brains of babies with microcephaly, adding to growing evidence of a link between the mosquito-transmitted virus and the birth defect.
According to the Brazilian Health Ministry, the suspected and confirmed cases of microcephaly linked to the Zika virus had increased to 4,443 as of Feb 13, from 4,314 a week earlier.
Microcephaly cases rare in Singapore, say docs
The ministry said it had confirmed 508 of those cases as either microcephaly or other changes to the central nervous system.
Three Brazilian doctors told Mind & Body that their pregnant patients live in fear of Zika, with some rushing to the emergency department for minor symptoms that may be unrelated to the virus.
Yet in the current sweltering summer heat of Brazil, it is not uncommon to see pregnant women exposing their limbs in short dresses.
In Brazil, the virus can be picked up using two different blood tests - one which identifies the presence of genetic material of the virus and the other which detects specific antibodies against the virus.
Dr Werner said the second test will be used routinely in public hospitals soon, as it can test for the presence of the Zika virus even in those without symptoms. This is because four in five patients have no symptoms.
Dr Pedro said these tests are in need of greater distribution in the Brazilian health systems.
In Singapore, doctors have said that cases of microcephaly are rare, with not even a single case seen at the National University Hospital (NUH) in the last five years.
Associate Professor Chan Shiao-Yng, a consultant at NUH Women's Centre, warned that the virus could be transmitted to the baby at all stages of a pregnancy.
She said much remains unknown about Zika - whether all or a proportion of infected mothers will transmit the virus to their foetuses or what proportion of the potentially infected babies actually display detectable abnormalities.
According to the Ministry of Health here, there is no evidence so far to suggest that pregnant women are more susceptible to Zika virus infection or will experience more severe disease.
Professor Victor Samuel Rajadurai, head and senior consultant at the department of neonatology at KK Women's and Children's Hospital, said most cases of microcephaly here are due to chromosomal abnormalities or intrauterine infections .
He said microcephaly cannot be reversed by medical treatment. These children undergo rehabilitation which includes environmental stimulation, physiotherapy, and speech and occupational therapy.
Within South-east Asia, sporadic cases of Zika have been detected in Cambodia, Indonesia, the Philippines, East Malaysia and Thailand.
It may be a matter of time before Singapore sees its first case as people travel and as Aedes mosquitoes, which also spread dengue and chikungunya, are present.
"Singaporeans should be concerned, but not overly alarmed," assured Dr Lim Poh Lian, head of the infectious diseases department at the Institute of Infectious Diseases and Epidemiology at TanTock Seng Hospital.