Fetal mortality and cleft lip with or without cleft palate

Birth order and oral clefts: a meta analysis

BACKGROUND

There is evidence that late birth order is associated with some complex disorders. For orofacial clefts there is no consensus as to whether increased birth order is associated or not. A meta-analysis of published data on cleft lip or cleft palate (CL/P and CP) was carried out to ascertain whether there is an increased risk for children of high birth order to have an oral cleft.

METHODS

All data available with information regarding the frequency of live births and CL/P and CP cases by birth order (1, 2, 3, and 4 or more) were included in the analysis, and the birth order category "1" was considered to be with no risk (OR = 1.0).

RESULTS

Children with higher birth order are more likely to have CL/P and CP with odds ratios increasing with birth order to a peak of 3.0 in children birth order "4 or more." Results are not different when isolated and syndromic cases are combined.

CONCLUSIONS

CL/P and CP occurrence is correlated with increasing birth order. Further studies, taking into consideration sample size and factors such as income status, race, paternal age, vitamin intake, and social habits, should be done to determine conclusively the association between birth order and oral clefts.

Reproductive history of mothers of children with solitary, nonsyndromic cleft lip and/or palate

The reproductive history was studied to evaluate if the three types of solitary, nonsyndromic clefts: cleft lip (CL), cleft lip and palate (CLP), and cleft palate (CP) are homogeneous entities. Occurrence of fetal loss, maternal health, and drug consumption of the mother during the pregnancy were compared in cases involving three types of clefts. Data was gathered from 87 children with clefts, 55 males and 32 females. Spontaneous abortions and vaginal bleeding were found to occur significantly more often in the (older) mother of a CLP child. This suggests that the factors involved in the etiology of CLP differ from the factors involved in CL and CP. Therefore, grouping of data of the three types of clefts in studies on the etiology should be avoided.

New study on the relationship between oral clefts and fetal loss

The sibships of 741 non-syndromic individuals with cleft lip with or without cleft palate (CL +/- P), those of 115 subjects with isolated cleft palate (CP), plus 2 series of controls of the same size were studied in a variety of ways. The 2 most significant findings were a) a higher fetal loss in the sibships of probands of the most frequently affected sex (CL +/- P: male; CP: female) and b) increased fetal mortality in the sibships with sporadic cases of CL +/- P when compared to that found in sibships with more than one affected. In general the results do not support the hypothesis of a causal relationship between fetal death and non-syndromic CL +/- P or CP.

Maternal fertility, reproductive loss, and defective human embryos

It is possible that many abnormal conceptuses are lost at an early stage without the mother's knowledge. To investigate this further the reproductive history of the mothers of defective embryos (neural tube defects, holoprosencephaly, cleft lip, polydactyly, and early embryonic resorption) was compared with that of the mothers of normal embryos. The frequency of prior miscarriages was higher in the case mothers than in normal controls matched for maternal age and gravidity, the difference being significant for all the anomalies except for polydactyly. The case mothers had fewer prior recognised pregnancies than control mothers matched for maternal age. There were more primigravid mothers in abnormal groups, and the difference from controls was significant for neural tube defects. It was assumed that the gravidity of the case mothers may be underestimated, possibly due to increased early abortions which are not recognised clinically. Thus, it seems that both recognised and unrecognised abortions occur more often in the mothers of defective embryos. Since many spontaneous abortuses are morphologically and/or cytogenetically abnormal, some women appear to conceive abnormal embryos repeatedly. Most of these embryos, however, may be screened out prenatally and escape clinical detection. Information on prior reproductive history of the woman should be examined carefully in genetic counselling.

Fetal mortality in sibships with one or more affected members with oral clefts

We investigated the fetal mortality in 903 sibships with at least one member having cleft lip with or without cleft palate [CL(P)] and 213 with at least one individual affected with cleft palate (CP) derived from three different data sources in México. The frequency of fetal wastage (abortion and/or stillbirth) was not increased in sibships where the propositi had cleft lip and palate (CLP) as compared with cleft lip (CL) nor in those where index cases had a bilateral lesion as compared to a unilateral one, nor when the index cases with CL(P) were female rather than males, nor when the index case was a female with bilateral lesion as compared to males with a unilateral one. Similarly fetal mortality was not increased in sibships in which the propositus had CP compared to those in which the index case was a female. These findings are contrary to some reports that claim to support a two-threshold model according to which individuals reaching the first one would be born with an oral cleft, and those reaching the second would be aborted. Our results, together with others, suggest the possibility that liability to oral clefts is independent of liability to fetal wastage.

Maternal reproductive loss and cleft lip with or without cleft palate in human embryos

Recognized spontaneous abortions in previous pregnancies were significantly more frequent in mothers of 87 Japanese embryos with cleft lip with or without cleft palate (CL(P] than in mothers of normal embryos. The number of prior pregnancies was found to be smaller in mothers of CL(P) embryos with additional defects, suggesting that unrecognized abortions might also occur more frequently in these women. The higher incidence of abortions was associated with more severe forms of CL(P), ie, CL(P) with associated anomalies rather than isolated CL(P), and bilateral rather than unilateral CL. These results are compatible with the "multifactorial two-threshold" model with a lower threshold beyond which the malformation occurs and a higher one beyond which the embryo dies. The present results are in contrast with the reduced spontaneous abortion rates in families of CL(P) probands reported previously. The reduced rates may be due to selection of those families in which CL(P) embryos escaped spontaneous abortion and survived to birth, although the effects of compensatory reproduction or maternal recall bias in postnatal data cannot be ruled out completely.

Fetal mortality in oral cleft families (V): Studies of sporadic vs familial and pure vs syndromic clefts

The frequencies of fetal deaths in sibships of oral cleft probands are analysed in relation to sporadic or familial clefts, and pure or syndromic clefts. In a study of 1823 pregnancies in 630 sibships of probands with CL(P), the frequency of fetal deaths was found to be increased, but not significantly, in the sporadic group as compared to the familial group of sibships from Indiana. However, such an increase was found to be significant in the Montreal data. The pooled data from both these centers also show a significant increase in the sporadic group. For CP, no such differences were found. Similar comparisons of fetal mortality in relation to pure and syndromic clefts indicated that the frequencies of fetal deaths were consistently elevated in sibships of probands with syndromic clefts with one exception, which is the Indiana CP group where the lowest frequency of fetal deaths was observed in the sibships. This group mostly consisted of sibships with solitary pregnancies. This may have been a result of early zygotic mortality in this group. Further data will be obtained to confirm this observation.

Fetal mortality in oral cleft families (VII): Birth intervals

Birth intervals in sibships of oral cleft probands are analysed to detect prolonged delays between successive pregnancies. Such intervals are useful indicators of undetected fetal mortality. The present study indicates that the average interval for 462 cleft families in Indiana is 30.61 months. The average interval leading to the birth of a cleft child is 33.94 and is significantly greater than the average interval for the entire sample. Although the contraception status of the Indiana population is not known, the significantly greater delay preceding the birth of a cleft child is indicative of a cause other than contraception. This finding is in agreement with the report by Drillien et al. (1966) that abnormal conceptions occur more frequently adjacent to cleft offspring. It is interesting that some increase in the average interval is also noted in the present study immediately following the birth of a cleft child. Such delays occurring both preceding and following the birth of a cleft child (in contrast to smaller intervals for other pregnancies in the same sibships) may indicate excessive fetal wastage due to a combination of genetic and environmental factors.

Additional data on spontaneous abortion and facial cleft malformations

Examination of fetal wastage data for a large collection of CL +/- P and CP sibships reported previously (Bear 1978) does not indicate the frequency of recognized abortion to be higher in the sibships of CL + P vs CL index cases, female vs male CL +/- P index cases, bilateral vs unilateral CL +/- P index cases, female bilateral CL +/- P index cases vs male unilateral CL +/- P index cases, or male vs female CP index cases. These observations fail to confirm those reported by Dronamraju (Dronamraju et al. 1982, Dronamraju & Bixler 1983a, b), and provide no evidence of a positive relation between degree of liability to facial cleft malformation and fetal mortality.

Fetal mortality in oral cleft families(IV): the "doubling effect"

Fetal mortality data from Lancaster, Penn., Chicago, Ill. and Minneapolis, Minn. are presented which support the authors' earlier findings in Indiana and Montreal that a positive relationship exists between the degree of liability to malformation and the incidence of fetal deaths in probands' sibships. Altogether, the study involved 189 CL sibships, 690 CLP sibships, and 3,416 pregnancies. On the basis of these data, which are derived from families of several different backgrounds of European ancestry, it is generalized that, as we proceed from CL sibships to CLP sibships, there is a doubling effect on fetal mortality. The consistency of this finding in several population samples is impressive. The implications of this observation are discussed with reference to genetic counseling.

Fetal mortality in oral cleft families: data from Indiana and Montreal

Analysis of 418 sibships of oral cleft probands from Indiana, and 288 sibships from Montreal indicate that the incidence of fetal mortality is significantly greater in sibships of probands with cleft lip and cleft palate (CLP) as compared to that in sibships of probands with cleft lip (CL) alone. These findings support a multifactorial-two-threshold concept, according to which a lower level of liability results in clefting whereas a higher level of liability causes fetal deaths. They add confirmatory evidence in support of the authors' earlier work, utilizing data from two different sources.