The incidence of multiple births was studied using the maternity records of 5750 Hausa women living in the savannah zone of Nigeria. There were 40 twins and 2 triplets/1000 births. Twenty six per cent of twins were monozygous. The incidence of multiple births, which was about five times higher than that observed in any western population, was significantly lower than that of other ethnic groups, who live in the hot and humid climate of the southern pat of country. The incidence of multiple births was related to maternal age but did not bear any association to the climate or prevalence of malaria.
PIP: The incidence of multiple births among the Hausa population in Katsina, Nigeria, is studied. Hospital maternity records for 5750 women delivering in 1974-1978 revealed 228 sets of twins and 12 sets of triplets, for a twinning rate of 39.7/1000 births, a triplet rate of 2.1/1000 births and a multiple birth rate of 41.7/1000; about 4 times the rate in Western countries. Data from the hospital's catchment area indicate that the results are valid for the area, but lower than for other parts of Nigeria. The incidence increased gradually with advancing maternal age, peaking at 30-34 years. The twinning rate gradually increased with birth order, with peak incidence at parity 5. The greatest incidence of triplets occurred at parity 7 or above, lower parities showed no consistent trend. Age and parity had independent effects of the twinning rate; the results are similar to those obtained in other studies. The most common presentation for twins was vertex/vertex (60%); for triplets, vertex/vertex/breech. Of the 190 cases where the twins' sex was recorded, 63.2% were like-sexed. The sex ratio was 1.29. Of 9 sets of triplets, 3 sets were all male, 3 all female, and 3 mixed. The sex ratio was 1.08. 26.3% of the twins were monozygous. Advancing maternal age had a more profound effect on the incidence of dizygous twins than on monozygous twins. The mean birth weight of the twins was 2.2 kg and for triplets 1.7 kg; lower than for full term singleton Hausa infants. Among the twins, 51 were stillborn and mortality was higher among like-sexed infants. Among the triplets, 6 were stillborn. Pregnancy duration averaged 268.5 days and was lower than singleton deliveries. Complications associated with twins included: prematurity (11.5% of the cases), postpartum hemorrhage (1.6%), and hydramnios (.9%). The effects of climate on the multiple birth rate is unclear. Some studies have shown a higher incidence in hot, humid climates. In this study, a higher incidence was observed among conceptions occurring in the cold, dry season. Some researchers have suggested a causal relationship between malaria and the incidence of twinning which was not confirmed in this study.