Some 1,118 new-born children had congenital abnormalities out of a total 25,386 admissions over a five-year period in six federal hospitals, according to a review.

The hospitals were chosen to represent data in their respective geopolitical zones: University of Ilorin Teaching Hospital, Ilorin; Obafemi Awolowo University Teaching Hospital, Ile-Ife; Ahmadu Bello Univesity Teaching Hospital, Zaria; Federal Medical Centre, Gombe; University of Calabar Teaching Hosptial, Calabar; and Imo State University Teaching Hospital.

The finding means birth defects are as high as 44 out of every 1,000 newborns, but the burden is still unknown, according to the National Expert Meeting on Birth Defect Surveillance and Prevention, which did the review last year.

Olubunmi Lawal-Aiyedun, founder of Spina Bifida and Hydrocephalus Care Foundation, said the finding emerged after researchers reviewed birth data going back five years in teaching hospitals, and indicates a growing prevalence of birth defects.

Nine out of every 1,000 affected children died from birth defects, contributing to infant mortality figures in Nigeria, and goes unrecognised, said Lawal-Aiyedun.

Speaking at a workshop to raise awareness on birth defects in Abuja, she said congenital abnormalities are mostly misdiagnosed or not observed during pregnancy scans.

"Women are pregnant and ultrasound doesn't pick up [abnormalities]. You have to screen for it. It is not good enough to say the heart is pumping. The other parts are they okay."

Speaking at a workshop ahead of the second-ever Birth Defects Day in Abuja, Lawal-Aiyedun called for a survey to determine Nigeria's actual burden. It is unknown how many of the 7 million children born each year have a birth defect, and the cause of almost 66 percent of birth defects is still unknown, she said.

Hayat Gommaa, head of nursing services department at Ahmadu Bello University's faculty of medicine, advocated preconception health as a means of preventing birth defects. Gommaa said a required 0.4 milligramme of folic acid daily for men and women well before and during pregnancy could reduce the risk of congenital abnormalities.