Nearly six weeks have passed since Cyclone Nargis tore through much of Burma, killing tens of thousands of people. Relief agencies say the extent of the devastation remains uncertain because the Burmese government has prevented assessment teams from going into the hardest-hit areas. This week, the Burmese junta is allowing hundreds of relief workers - including foreigners - to fan out across the hard-hit Irawaddy Delta. VOA's Luis Ramirez reports from Bangkok.

Relief agencies hope the government's decision to allow about 250 foreign and Burmese relief workers into the delta to assess the needs of victims will give a more accurate sense of the scope of the devastation.

The government of Burma puts the number of dead and missing at 134,000, but has not updated the figure for weeks.

United Nations officials have relied on information provided by the government and the accounts of workers who have returned from the scene of the devastation. U.N. spokeswoman Amanda Pitt told reporters in Bangkok there is no reliable and comprehensive assessment of damage or casualties.

"Some areas of the delta have been completely devastated," she said. "There is nothing there at all, particularly where the tidal surge came in. Other areas are now functioning almost normally. So, there is huge sort of gaps and huge differences in how things have been affected. Some people have already started to get their lives back on track."

U.N. officials say relief workers have yet to reach roughly half of the 2.4 million people that the agencies estimate were severely affected by the storm.

Wednesday, the officials said expectant mothers are among the most vulnerable of the victims. The U.N. Population Fund's William Ryan estimates tens of thousands of pregnant women are among those who have not been reached yet.

"These women urgently need prenatal care and clean and safe delivery options," he said. "Pregnancy and childbirth in Myanmar were already dangerous, before the storm. The destruction of health centers and the loss of midwives have greatly increased the risks."

Ryan says his agency has started sending doctors to two hard-hit townships, last week, to provide prenatal exams.

"They found that many pregnant clients also needed counseling for emotional trauma and grief over the loss of their children and husbands. Most did not know where they would give birth," he said.

The Burmese military government's reluctance to allow relief agencies full access to the hard-hit region have raised concerns of a second wave of deaths due to disease, malnutrition, or exposure.

But U.N. officials say they have heard about cases of respiratory illnesses, diarrhea, and dengue fever, but no reports of major outbreaks.